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Street PHILADELPHIA 




THE LIBRARY 

OF 

THE UNIVERSITY 
OF CALIFORNIA 



PRESENTED BY 

PROF. CHARLES A. KOFOID AND 

MRS. PRUDENCE W. KOFOID 




PLEASUEES OF THE TELESCOPE 



PLEASUKES OF THE 
TELESCOPE 



AN ILLUSTRATED GUIDE FOR AMATEUR ASTRONOMERS 

AND A POPULAR DESCRIPTION OF THE CHIEF 

WONDERS OF THE HEAVENS FOR 

GENERAL READERS 



BY 

GARRETT P. SERVISS 

AUTHOR OF ASTRONOMY WITH AN OPERA-GLASS 



1 This being made, He yearned for worlds to make 
From other chaos out beyond our night 
For to create is still God^s prime delight. 
The large moon, all alone, sailed her dark lake, 
And the first tides were moving to her might ; 
Then Darkness trembled, and began to quake 
Big with the birth of stars, and when He spake 
A million worlds leapt into radiant light. 1 '' 

LLOYD MIFFLIN. 



WITH MANY ILLUSTRATIONS 



NEW YORK 
D. APPLETON AND COMPANY 

1901 



COPYRIGHT, 1901, 
BY D APPLETON AND COMPANY. 



PREFACE 



BY the introduction of a complete series of star maps, 
drawn specially for the use of the amateur and dis- 
tributed through the body of the work, thus facilitating 
consultation, it is believed that this book makes a step in 
advance of its predecessors. The maps show all of the 
stars visible to the naked eye in the regions of sky repre- 
sented, and, in addition, some stars that can only be seen 
with optical aid. The latter have been placed in the maps 
as guide posts in the telescopic field to assist those who 
are searching for faint and inconspicuous objects referred 
to in the text. As the book was not written for those who 
possess the equipment of an observatory, with telescopes 
driven by clockwork and provided with graduated circles, 
right ascensions and declinations are not given. All of 
the telescopic phenomena described are, however, repre- 
sented in the maps. Star clusters are indicated by a con- 
ventional symbol, and nebulae by a little white circle; 
while a small cross serves to mark the places where nota- 
ble new stars have appeared. The relative magnitudes of 
the stars are approximately shown by the dimensions of 
their symbols in the maps, the smaller stars being repre- 
sented by white dots and the larger by star-shaped figures. 

In regard to binary stars, it should be remembered 
that, in many cases, their distances and angles of posi- 
tion change so rapidly that any statement concerning 
them remains valid only for a few years at the most. 
There is also much confusion among the measurements 



vi PLEASURES OF THE TELESCOPE 

announced by different authorities. In general, the most 
recent measurements obtainable in 1900 are given in the 
text, but the observer who wishes to study close and rapid 
binaries will do well to revise his information about them 
as frequently as possible. An excellent list of double 
stars kept up to date, will be found in the annual Com- 
panion to the Observatory, published in London. 

In the lunar charts the plan of inserting the names of 
the principal formations has been preferred to that usually 
followed, of indicating them only by numbers, accompanied 
by a key list. Even in the most detailed charts of the 
moon only a part of what is visible with telescopes can be 
shown, and the representation, at best, must be merely 
approximate. It is simply a question of what to include 
and what to omit; and in the present case the probable 
needs of the amateur observer have governed the selec- 
tion readiness and convenience of reference being the 
chief aim. 

It should, perhaps, be said here that the various chap- 
ters composing this book like those of " Astronomy with 
an Opera-glass " were, in their original form, with the 
single exception of Chapter IX, published in Appletons' 
Popular Science Monthly. The author, it is needless to say, 
was much gratified by the expressed wish of many readers 
that these scattered papers should be revised and collected 
in a more permanent form. As bearing upon the general 
subject of the book, a chapter has been added, at the end, 
treating on the question of the existence of planets among 
the stars. This also first appeared in the periodical above 
mentioned. 

In conclusion, the author wishes for his readers as 
great a pleasure in the use of the telescope as he himself 
has enjoyed. GPS 

BOROUGH OF BROOKLYN, NEW YORK, January, 1901. 



CONTENTS 



CHAPTER I 

PAGE 

THE SELECTION AND TESTING OF A GLASS 1 

How to get a good telescope Difference between reflectors and 
refractors How a telescope is made achromatic The way to test a 
telescope on stars. 

CHAPTER II 
IN THE STARRY HEAVENS. 19 

Orion and its wonders, Lepus, Canis Major, Argo, Monoceros, 
Canis Minor, and the Head of Hydra. 

CHAPTER III 

FROM GEMINI TO LEO AND ROUND ABOUT 38 

The zodiacal constellations Gemini, Cancer, and Leo, and their 
neighbors Auriga, the Lynx, Hydra, Sextans, and Coma Berenices. 

CHAPTER IV 
VIRGO AND HER NEIGHBORS 57 

Crater and Corvus, Hydra, Virgo, the "Field of the Nebulae," 
Libra, Bootes, and the great Arcturus, Canes Venatici, and Corona 
Borealis. 

CHAPTER V 
IN SUMMER STAR-LANDS 75 

Scorpio and its red-green gem. Ophiuchus, Sagittarius, Scutum 
Sobieskii, Capricornus, Serpens, Hercules, Draco, Aquila, and Delphinus. 

CHAPTER VI 
FROM LYRA TO ERIDANUS v ... . .97 

Lyra and its brilliant Vega, Cygnus, Vulpecula, Aquarius, Equuleus, 
Pegasus, Cetus, and Eridanus. 

vii 



viii PLEASURES OF THE TELESCOPE 

CHAPTER VII 

PAGE 

PISCES, ARIES, TAURUS, AND THE NORTHERN MARS .... 117 

The first double star ever discovered, the Pleiades and their photo- 
graphic wonders, the Royal Family of the Sky, Andromeda, Cassiopeia, 
Perseus and Cepheus, Ursa Major, Camelopardalus, Ursa Minor, and the 
Pole Star. 

CHAPTER VIII 
SCENES ON THE PLANETS 139 

Jupiter, its belts and its moons Saturn, the ringed planet Saturn's 
moons and Roche's limit Mars and its white polar caps and so-called 
seas and continents Venus and her atmosphere The peculiar rota- 
tions of Venus and Mercury. 

CHAPTER IX 

THE MOUNTAINS AND PLAINS OF THE MOON AND THE SPECTACLES 

OF THE SUN 156 

Peculiarities of the lunar landscapes The sVcalled seas, the craters, 
the ring mountains, the inclosed plains, the mountain ranges, Tycho's 
mysterious streaks, and other lunar features described How to view 
the sun and its spots. 

CHAPTER X 

ARE THERE PLANETS AMONG THE STARS ? 183 

Significance of Dr. See's observations Why our telescopes do not 
show planets circling around distant suns Reasons for thinking that 
such planets may exist The bearing of stellar evolution on the ques- 
tion. 



PLEASURES OP THE TELESCOPE 



CHAPTER I 

THE SELECTION AND TESTING OF A GLASS 

"O telescope, instrument of much knowledge, more precious than any scep- 
ter! Is not he who holds thee in his hand made king and lord of the works of 
God ? " JOHN KEPLER. 

IF the pure and elevated pleasure to be derived from 
the possession and use of a good telescope of three, four, 
five, or six inches aperture were generally known, I am 
certain that no instrument of science would be more com- 
monly found in the homes of intelligent people. The 
writer, when a boy, discovered unexpected powers in a 
pocket telescope not more than fourteen inches long when 
extended, and magnifying ten or twelve times. It became 
his dream, which was afterward realized, to possess a 
more powerful telescope, a real astronomical glass, with 
which he could see the beauties of the double stars, the 
craters of the moon, the spots on the sun, the belts and 
satellites of Jupiter, the rings .of Saturn, the extraor- 
dinary shapes of the nebula, the crowds of stars in the 
Milky Way, and the great stellar clusters. And now he 
would do what he can to persuade others, who perhaps 
are not aware how near at hand it lies, to look for them- 
selves into the wonder-world of the astronomers. 

There is only one way in which you can be sure of 
getting a good telescope. First, decide how large a glass 
you are to have, then go to a maker of established reputa- 



2 PLEASURES OF THE TELESCOPE 

tion, fix upon the price you are willing to pay remem- 
bering that good work is never cheap and finally see 
that the instrument furnished to you answers the proper 
tests for a telescope of its size. There are telescopes and 
telescopes. Occasionally a rare combination of perfect 
homogeneity in the material, complete harmony between 
the two kinds of glass of which the objective is composed, 
and lens surfaces whose curves are absolutely right, pro- 
duces a telescope whose owner would part with his last 
dollar sooner than with it. Such treasures of the lens- 
maker's art can not, perhaps, be commanded at will, yet, 
they are turned out with increasing frequency, and the 
best artists are generally able, at all times, to approxi- 
mate so closely to perfection that any shortcoming may 
be disregarded. 

In what is said above I refer, of course, to the refract- 
ing telescope, which is the form of instrument that I 
should recommend to all amateurs in preference to the 
reflector. But, before proceeding further, it may be well 
to recall briefly the principal points of difference between 
these two kinds of telescopes. The purpose of a telescope 
of either description is, first, to form an image of the 
object looked at by concentrating at a focus the rays of 
light proceeding from that object. The refractor achieves 
this by means of a carefully shaped lens, called the object 
glass, or objective. The reflector, on the other hand, 
forms the image at the focus of a concave mirror. 

A very pretty little experiment, which illustrates these 
two methods of forming an optical image, and, by way of 
corollary, exemplifies the essential difference between re- 
fracting and reflecting telescopes, may be performed by 
any one who possesses a reading glass and a magnifying 
hand mirror. In a room that is not too brightly illumi- 
nated pin a sheet of white paper on the wall opposite to a 



THE SELECTION AND TESTING OF A GLASS 3 

window that, by preference, should face the north, or 
away from the position of the sun. Taking first the read- 
ing glass, hold it between the window and the wall paral- 




IMAGE AT THE Focus OF A LENS. 

lei to the sheet of paper, and a foot or more distant from 
the latter. By moving it to and fro a little you wil be able 
to find a distance, corresponding to the focal length of the 
lens, at which a picture of the window is formed on the 
paper. This picture, or image, will be upside down, be- 
cause the rays of light cross at the focus. By moving the 
glass a little closer to the wall you will cause the picture 



4 PLEASURES OF THE TELESCOPE 

of the window to become indistinct, while a beautiful im- 
age of the houses, trees, or other objects of the outdoor 
world beyond, will be formed upon the paper. We thus 
learn that the distance of the image 'from the lens varies 
with the distance of the object whose image is formed. 
In precisely a similar manner an image is formed at the 
focus of the object glass of a refracting telescope. 




IMAGE AT THE Focus OF A CONCAVE MIRROR. 



Take next your magnifying or concave mirror, and 
detaching the sheet of paper from the wall, hold it nearly 
in front of the mirror between the latter and the window. 



THE SELECTION AND TESTING OF A GLASS 5 

When you have adjusted the distance to the focal length 
of the mirror, you will see an image of the window pro- 
jected upon the paper, and by varying the distance, as 
before, you will be able to produce, at will, pictures of 
nearer or more remote objects. It is in this way that 
images are formed at the focus of the mirror of a reflect- 
ing telescope. 

Now, you w r ill have observed that the chief apparent 
difference between these two methods of forming an im- 
age of distant objects is that in the first case the rays of 
light, passing through the transparent lens, are brought 
to a focus on the side opposite to that where the real 
object is, while in the second case the rays, being reflected 
from the brilliant surface of the opaque mirror, come 
to a focus on the same side as that on which the object 
itself is. From this follows the most striking difference 
in the method of using refracting and reflecting tele- 
scopes. In the refractor the observer looks toward the 
object; in the reflector he looks away from it. Sir Wil- 
liam Herschel made his great discoveries with his back to 
the sky. He used reflecting telescopes. This principle, 
again, can be readily illustrated by means of our simple 
experiment with a reading glass and a magnifying mirror. 
Hold the reading glass between the eye and a distant 
object with one hand, and with the other hand place a 
smaller lens such as a pocket magnifier, near the eye, and 
in line with the reading glass. Move the two carefully 
until they are at a distance apart equal to the sum of the 
focal lengths of the lenses, and you will see a magnified 
image of the distant object. In other words, you have 
constructed a simple refracting telescope. Then take the 
magnifying mirror, and, turning your back to the object 
to be looked at, use the small lens as before that is to 
say, hold it- between your eye and the mirror, so that its 



6 PLEASURES OF THE TELESCOPE 

distance from the latter is equal to the sum of the focal 
lengths of the mirror and the lens, and you will see again 
a magnified image of the distant object. This time it is 
a reflecting telescope that you hold in your hands. 

The magnification of the image reminds us of the 
second purpose which is subserved by a telescope. A 
telescope, whether* refracting or reflecting, consists of 
two essential parts, the first being a lens, or a mirror, to 
form an image, and the second a microscope, called an 
eyepiece, to magnify the image. The same eyepieces will 
serve for either the reflector or the refractor. But in 
order that the magnification may be effective, and serve 
to reveal what could not be seen without it, the image 
itself must be as nearly perfect as possible; this requires 
that every ray of light that forms the image shall be 
brought to a point in the image precisely corresponding 
to that from which it emanates in the real object. In 
reflectors this is effected by giving a parabolic form to 
the concave surface of the mirror. In refractors there is 
a twofold difficulty to be overcome. In the first place, a 
lens with spherical surfaces does not bend all the rays 
that pass through it to a focus at precisely the same dis- 
tance. The rays that pass near the outer edge of the 
lens have a shorter focus than that of the rays which pass 
near the center of the lens; this is called spherical aberra- 
tion. A similar phenomenon occurs with a concave mir- 
ror whose surface is spherical. In that case, as we have 
seen, the difficulty is overcome by giving the mirror a 
parabolic instead of a spherical form. In an analogous 
way the spherical aberration of a lens can be corrected 
by altering its curves, but the second difficulty that arises 
with a lens is not so easily disposed of: this is what is 
called chromatic aberration. It is due to the fact that 
the rays belonging to different parts of the spectrum have 



TEE SELECTION AND TESTING OF A GLASS 7 

different degrees of refrangibility, or, in other words, that 
they come to a focus at different distances from the lens; 
and this is independent of the form of the lens. The blue 
rays come to a focus first, then the yellow, and finally the 
red. It results from this scattering of the spectral rays 
along the axis of the lens that there is no single and exact 
focus where all meet, and that the image of a star, for 
instance, formed by an ordinary lens, even if the spherical 
aberration has been corrected, appears blurred and dis- 
colored. There is no such difficulty with a mirror, be- 
cause there is in that case no refraction of the light, and 
consequently no splitting up of the elements of the spec- 
trum. 

In order to get around the obstacle formed by chro- 
matic aberration it is necessary to make the object glass 
of a refractor consist of two lenses, each composed of a 
different kind of glass. One of the most interesting facts 
in the history of the telescope is that Sir Isaac Newton 
could see no hope that chromatic aberration would be 
overcome, and accordingly turned his attention to the 
improvement of the reflecting telescope and devised a 
form of that instrument which still goes under his name. 
And even after Chester More Hall in 1729, and John Dol- 
lond in 1757, had shown that chromatic aberration could 
be nearly eliminated by the combination of a flint-glass 
lens with one of crown glass, William Herschel, who 
began his observations in 1774, devoted his skill entirely 
to the making of reflectors, seeing no prospect of much 
advance in the power of refractors. 

A refracting telescope which has been freed from the 
effects of chromatic aberration is called achromatic. The 
principle upon which its construction depends is that by 
combining lenses of different dispersive power the separa- 
tion of the spectral colors in the image can be corrected 



8 



PLEASURES OF THE TELESCOPE 




ACHROMATIC OBJECT GLASS. 
a, crown glass ; 6, fliat glass. 



while the convergence of the rays of light toward a focus 
is not destroyed. Flint glass effects a greater dispersion 
than crown glass nearly in the ratio of three to two. 

The chromatic combination 
consists of a convex lens 
of crown backed by a con- 
cave, or plano-concave, lens 
of flint. When these two 
lenses are made of focal 
lengths which are directly 
proportional to their dis- 
persions, they give a prac- 
tically colorless image at 
their common focus. The 
skill of the telescope-maker 
and the excellence of his work depend upon the selection 
of the glasses to be combined and his manipulation of the 
curves of the lenses. 

Now, the reader may ask, " Since reflectors require no 
correction for color dispersion, while that correction is 
only approximately effected by the combination of two 
kinds of lenses and two kinds of glass in a refractor, why 
is not the reflector preferable to the refractor? " 

The answer is, that the refractor gives more light and 
better definition. It is superior in the first respect be- 
cause a lens transmits more light than a mirror reflects. 
Professor Young has remarked that about eighty-two per 
cent of the light reaches the eye in a good refractor, while 
" in a Newtonian reflector, in average condition, the per- 
centage seldom exceeds fifty per cent, and more frequently 
is lower than higher." The superiority of the refractor in 
regard to definition arises from the fact that any dis- 
tortion at the surface of a mirror affects the direction of 
a ray of light three times as much as the same distortion 



THE SELECTION AND TESTING OF A GLASS 9 

would do at the surface of a lens. And this applies 
equally both to permanent errors of curvature and to tem- 
porary distortions produced by strains and by inequality 
of temperature. The perfect achromatism of a reflector 
is, of course, a great advantage, but the chromatic aber- 
ration of refractors is now so well corrected that their 
inferiority in that respect may be disregarded. It must 
be admitted that reflectors are cheaper and easier to 
make, but, on the other hand, they require more care, and 
their mirrors frequently need resilvering, while an object 
glass with reasonable care never gets seriously out of 
order, and will last for many a lifetime. 

Enough has now, perhaps, been said about the respec- 
tive properties of object glasses and mirrors, but a word 
should be added concerning eyepieces. Without a good 
eyepiece the best telescope will not perform well. The 
simplest of all eyepieces is a single double-convex lens. 
With such a lens the magnifying power of the telescope 
is measured by the ratio of the focal length of the objec- 
tive to that of the eye lens. Suppose the first is sixty 
inches and the latter half an inch; then the magnifying 
power will be a hundred and twenty diameters i. e., the 
disk of a planet, for instance, will be enlarged a hundred 
and twenty times along each diameter, and its area will 
be enlarged the square of a hundred and twenty, or four- 
teen thousand four hundred times. But in reckoning 
magnifying power, diameter, not area, is always consid- 
ered. For practical use an eyepiece composed of an ordi- 
nary single lens is seldom advantageous, because good 
definition can only be obtained in the center of the field. 
Lenses made according to special formula?, however, and 
called solid eyepieces, give excellent results, and for high 
powers are often to be preferred to any other. The eye- 
pieces usually furnished with telescopes are, in their 



10 



PLEASURES OF THE TELESCOPE 



essential principles, compound microscopes, and they are 
of two descriptions, " positive " and " negative." The for- 
mer generally goes under the name of its inventor, Hams- 
den, and the latter is name'd 'after the great Dutch astron- 
omer, Huygens. The Huygens eyepiece consists of two 



NEGATIVE EYEPIECE. 



POSITIVE EYEPIECE. 



plano-convex lenses whose focal lengths are in the ratio 
of three to one. The smaller lens is placed next to the 
eye. Both lenses have their convex surfaces toward the 
object glass, and their distance apart is equal to half the 
sum of their focal lengths. In this kind of eyepiece the 
image is formed between the two lenses, and if the work 
is properly done such an eyepiece is achromatic. It ,is 
therefore generally preferred for mere seeing purposes. 
In the Ramsden eyepiece two plano-convex lenses are also 
used, but they are of equal focal length, are placed at a 
distance apart equal to two thirds of the focal length of 
either, and have their convex sides facing one another. 
With such an eyepiece the image viewed is beyond the 
farther or field lens instead of between the two lenses, and 
as this fact renders it easier to adjust wires or lines for 
measuring purposes in the focus of the eyepiece, the 
Ramsden construction is used when a micrometer is to 
be employed. In order to ascertain the magnifying power 
which an eyepiece gives when applied to a telescope it 
is necessary to know the equivalent, or combined, focal 
length of the two lenses. Two simple rules, easily re- 
membered, supply the means of ascertaining this. The 
equivalent focal length of a negative or Huygens eyepiece 



THE SELECTION AND TESTING OF A GLASS H 

is equal to half the focal length of the larger or field lens. 
The equivalent focal length of a positive or Ramsden eye- 
piece is equal to three fourths of the focal length of either 
of the lenses. Having ascertained the equivalent focal 
length of the eyepiece, it is only necessary to divide it into 
the focal length of the object glass (or mirror) in order to 
know the magnifying power of your telescope when that 
particular eyepiece is in use. 

A first-class object glass (or mirror) will bear a mag- 
nifying power of one hundred to the inch of aperture 
when the air is in good condition that is, if you are look- 
ing at stars. If you are viewing the moon, or a planet, 
better results will always be obtained with lower powers 
say fifty to the inch at the most. And under ordinary 
atmospheric conditions a power of from fifty to seventy- 
five to the inch is far better for stars than a higher power. 
With a five-inch telescope that would mean from two hun- 
dred and fifty to three hundred and seventy-five diame- 
ters, and such powers should only be applied for the sake 
of separating very close double stars. As a general rule, 
the lowest power that will distinctly show what you de- 
sire to see gives the best results. The experienced ob- 
server never uses as high powers as the beginner does. 
The number of eyepieces purchased with a telescope should 
never be less than three a very low power say ten to 
the inch; a very high power, seventy-five or one hundred 
to the inch, for occasional use; and a medium power say 
forty to the inch for general use. If you can afford it, 
get a full battery of eyepieces six or eight, or a dozen 
for experience shows that different objects require differ- 
ent powers in order to be best seen, and, moreover, a slight 
change of power is frequently a great relief to the eye. 

There is one other thing of great importance to be 
considered in purchasing a telescope the mounting. If 



12 PLEASURES OF THE TELESCOPE 

your glass is not well mounted on a steady and easily 
managed stand, you might better have spent your money 
for something more useful. I have endured hours of tor- 
ment while trying to see stars through a telescope that 
was shivering in the wind and dancing to every motion 
of the bystanders, to say nothing of the wriggling contor- 
tions caused by the application of my own fingers to the 
focusing screw. The best of all stands is a solid iron 
pillar firmly fastened into a brick or stone pier, sunk at 
least four feet in the ground, and surmounted by a well- 
made equatorial bearing whose polar axis has been care- 
fully placed in the meridian. It can be readily protected 
from the weather by means of a wooden hood or a rubber 
sheet, while the tube of the telescope may be kept indoors, 
being carried out and placed on its bearing only when ob- 
servations are to be made. With such a mounting you 
can laugh at the observatories with their cumbersome 
domes, for the best of all observatories is the open air. 
But if you dislike the labor'of carrying and adjusting the 
tube every time it is used, and are both fond of and able 
to procure luxuries, then, after all, perhaps, you had 
better have the observatory, dome, draughts and all. 

The next best thing in the way of a mounting is a port- 
able tripod stand. This may be furnished either with 
an equatorial bearing for the telescope, or an altazimuth 
arrangement which permits both up-and-down and hori- 
zontal motions. The latter is cheaper than the equatorial 
and proportionately inferior in usefulness and conven- 
ience. The essential principle of the equatorial bearing 
is motion about two axes placed at right angles to one 
another. When the polar axis is in the meridian, and in- 
clined at an angle equal to the latitude of the place, the 
telescope can be moved about the two axes in such a way 
as to point to any quarter of the sky, and the motion of a 



THE SELECTION AND TESTING OF A GLASS 13 

star, arising from the earth's rotation, can be followed 
hour after hour without disturbing the instrument. 
When thus mounted, the telescope may be driven by clock- 
work, or by hand with the aid of a screw geared to a 
handle carrying a universal joint. 

And now for testing the telescope. It has already 
been remarked that the excellence of a telescope depends 
upon the perfection of the image formed at the focus of 
the objective. In what follows I have only a refractor in 
mind, although the same principles would apply to a re- 
flector. With a little practice anybody who has a correct 
eye can form a fair judgment of the excellence of a tele- 
scopic image. Suppose we have our telescope steadily 
mounted out of doors (if you value your peace of mind you 
will not try to use a telescope pointed out of a window, 
especially in winter), and suppose we begin our observa- 
tions with the pole star, employing a magnifying power of 
sixty or seventy to the inch. Our first object is to see if 
the optician has given us a good glass. If the air is not 
reasonably steady we had better postpone our experiment 
to another night, because we shall find that the star as 
seen in the telescope flickers and " boils," and behaves in 
so extraordinary a fashion that there is no more defini- 
tion in the image than there is steadiness in a bluebottle 
buzzing on a window pane. But if the night is a fine one 
the star image will be quiescent, and then we may note the 
following particulars: The real image is a minute bright 
disk, about one second of arc in diameter if we are using a 
four-and-a-half or five-inch telescope, and surrounded by 
one very thin ring of light, and the fragments, so to speak, 
of one or possibly two similar rings a little farther from 
the disk, and visible, perhaps, only by glimpses. These 
" diffraction rings " arise from the undulatory nature of 
light, and their distance apart as well as the diameter of 



14: PLEASURES OF THE TELESCOPE 

the central disk depend upon the length of the waves of 
light. If the telescope is a really good one, and both 
object glass and eyepiece are properly adjusted, the disk 
will be perfectly round, slightly softer at the edge, but 
otherwise equally bright throughout; and the ring or 
rings surrounding it will be exactly concentric, and not 
brighter on one side than on another. Even if our tele- 
scope were only two inches or two inches and a half in 
aperture we should at once notice a little bluish star, the 
mere ghost of a star in a small telescope, hovering near 
the polar star. It is the celebrated " companion," but we 
shall see it again wnen we have more time to study it. 
Now let us put the star out of focus by turning the focusing 
screw. Suppose we turn it in such a way that the eyepiece 
moves slightly outside the focus, or away from 
the object glass. Very beautiful phenomena im- 
mediately begin to make their appearance. A 
slight motion outward causes the little disk 
to expand perceptibly, and just as this expan- 
sion commences, a bright-red point appears at the precise 
center of the disk. But, the outward motion continuing, 
this red center disappears, and is replaced by a blue 
center, which gradually expands into a sort of flare 
over the middle of the disk. The disk itself has in 
the mean time enlarged into a series of concentric bright 
rings, graduated in luminosity with beautiful precision 
from center toward circumference. The outermost ring 
is considerably brighter, however, than it would be if 
the same gradation applied to it as applies to the inner 
rings, and it is surrounded, moreover, on its outer edge 
by a slight flare which tends to increase its apparent 
width. Next let us return to the focus and then move 
the eyepiece gradually inside the focal point or plane. 
Once more the star disk expands into a series of circles, 




THE SELECTION AND TESTING OF A GLASS 15 

and, if we except the color phenomena noticed outside the 
focus, these circles are precisely like those seen before in 
arrangement, in size, and in brightness. If they were not 
the same, we should pronounce the telescope to be im- 
perfect. There is one other difference, however, besides 
the absence of the blue central flare, and that is a faint 
reddish edging around the outer ring when the expansion 
inside the focus is not carried very far. Upon continuing 
to move the eyepiece inside or outside the focus we ob- 
serve that the system of rings becomes larger, while the 
rings themselves rapidly increase in number, becoming at 
the same time individually thinner and fainter. 

By studying the appearance of the star disk when in 
focus and of the rings when out of focus on either side, an 
experienced eye can readily detect any fault that a tele- 
scope may have. The amateur, of course, can only learn 
to do this by considerable practice. Any glaring and seri- 
ous fault, however, will easily make itself manifest. Sup- 
pose, for example, we observe that the image of a star 
instead of being perfectly round is oblong, and that a simi- 
lar defect appears in the form of the rings when the eye- 
piece is put out of focus. We know at once that some- 
thing is wrong; but the trouble may lie either in the ob- 
ject glass, in the eyepiece, in the eye of the observer him- 
self, or in the adjustment of the lenses in the tube. A 
careful examination of the image and the out-of-focus 
circles will enable us to determine with which of these 
sources of error we have to deal. If the star image when 
in focus has a sort of wing on one side, and if the rings 
out of focus expand eccentrically, appearing wider and 
larger on one side than on the other, being at the same 
time brightest on the least expanded side, then the object 
glass is probably not at right angles to the axis of the 
tube and requires readjustment. That part of the object 



16 PLEASURES OF THE TELESCOPE 

glass on the side where the rings appear most expanded 
and faintest needs to be pushed slightly inward. This 
can be effected by means of counterscrews placed for that 
purpose in or around the cell. But if, after we have got 
the object glass properly squared to the axis of the tube 
or the line of sight, the image and the ring system in and 
out of focus still appear oblong, the fault of astigmatism 
must exist either in the objective, the eyepiece, or the 
eye. The chances are very great that it is the eye itself 
that is at fault. We may be certain of this if we find, on 
turning the head so as to look into the telescope with 
the eye in different positions, that the oblong image turns 
with the head of the observer, keeping its major axis con- 
tinually in the same relative position with respect to the 
eye. The remedy then is to consult an oculist and get a 
pair of cylindrical eyeglasses. If the oblong image does 
not turn round with the eye, but does turn when the eye- 
piece is twisted round, then the astigmatism is in the lat- 
ter. If, finally, it does not follow either the eye or the 
eyepiece, it is the objective that is at fault. 

But instead of being oblong, the image and the rings 
may be misshapen in some other way. If they are three- 
cornered, it is probable that the object glass is subjected 
to undue pressure in its cell. This, if the telescope has 
been brought out on a cool night from a warm room, may 
arise from the unequal contraction of the metal work and 
the glass as they cool off. In fact, no good star image 
can be got while a telescope is assuming the temperature 
of the surrounding atmosphere. Even the air inclosed in 
the tube is capable of making much trouble until its tem- 
perature has sunk to the level of that outside. Half an 
hour at least is required for a telescope to adjust itself to 
out-of-door temperature, except in the summer time, and 
it is better to allow an hour or two for such adjustment in 



THE SELECTION AND TESTING OF A GLASS 



17 




cold weather. Any irregularity in the shape of the rings 
which persists after the lenses have been accurately ad- 
justed and the telescope has properly cooled may be as- 
cribed to imperfections, such as veins or spots of unequal 
density in the glass forming the 
objective. 

The spherical aberration of 
an object glass may be under- 
corrected or overcorrected. In 
the former case the central rings 
inside the focus will appear faint 

and the outer ones unduly strong, while outside the focus 
the central rings will be too bright and the outer ones too 
feeble. But if the aberration is overcorrected the central 
rings will be overbright inside the focus and abnormally 
faint outside the focus. 

Assuming that we have a telescope in which no ob- 
vious fault is discernible, the next thing is to test its pow- 



123 
THE OuT-OF-Focus RINGS. 
1, Correct figure ; 2 and 3, spher- 
ical aberration. 




Two VIEWS OF MARS IN 
The smaller with a three-and-three-eighths-inch telescope ; the larger with a nine-inch. 

ers in actual work. In what is to follow I shall endeavor 
to describe some of the principal objects in the heavens 
from which the amateur observer may expect to derive 
pleasure and instruction, and which may at the same time 



18 PLEASURES OF THE TELESCOPE 

serve as tests of the excellence of his telescope. No one 
should be deterred or discouraged in the study of celes- 
tial objects by the apparent insignificance of his means of 
observation. The accompanying pictures of the planet 
Mars may serve as an indication of the fact that a small 
telescope is frequently capable of doing work that ap- 
pears by no means contemptible when placed side by side 
with that of the greater instruments of the observatories. 



CHAPTER II 

IN THE STARRY HEAVENS 

" Now constellations, Muse, and signs rehearse; 
In order let them sparkle in thy verse." MANILIUS. 

LET us imagine ourselves the happy possessors of 
three properly mounted telescopes of five, four, and three 
inches aperture, respectively. A fine midwinter evening 
has come along, the air is clear, cool, and steady, and the 
heavens, of that almost invisible' violet which is reserved 
for the lovers of celestial scenery, are spangled with stars 
that hardly twinkle. We need not disturb our minds 
about a few thin clouds here and there floating lazily in 
the high air; they announce a change of weather, but 
they will not trouble us to-night. 

Which way shall we look? Our eyes will answer the 
question for us. However we may direct them, they in- 
stinctively return to the south, and are lifted to behold 
Orion in his glory, now near the meridian and midway to 
the zenith, with Taurus shaking the glittering Pleiades 
before him, and Canis Major with the flaming Dog Star 
following at his heels. 

Not only is Orion the most brilliant of all constella- 
tions to the casual star-gazer, but it contains the richest 
mines that the delver for telescopic treasures can any- 
where discover. We could not have made a better begin- 
ning, for here within a space of a few square degrees we 
have a wonderful variety of double stars and multiple 

19 



20 PLEASURES OF THE TELESCOPE 

stars, so close and delicate as to test the powers of the 
best telescopes, besides a profusion of star-clusters and 
nebulae, including one of the supreme marvels of space, 
the Great Nebula in the Sword. 

Our star map No. 1 will serve as a guide to the objects 
which we are about to inspect. Let us begin operations 
with our smallest telescope, the three-inch. I may re- 
mark here that, just as the lowest magnifying power that 
will clearly reveal the object looked for gives ordinarily 
better results than a higher power, so the smallest tele- 
scope that is competent to show what one wishes to see 
is likely to yield more satisfaction, as far as that particu- 
lar object is concerned, than a larger glass. The larger 
the object glass and the higher the power, the greater are 
the atmospheric difficulties. A small telescope will per- 
form very well on a night when a large one is helpless. 

Turn the glass upon /3 (Rigel), the white first-magni- 
tude star in Orion's left foot. Observe whether the image 
with a high power is clear, sharp, and free from irregular 
wisps of stray light. Look at the rings in and out of 
focus, and if you are satisfied with the performance, try 
for the companion. A good three-inch is certain to show 
it, except in a bad state of the atmosphere, and even then 
an expert can see it, at least by glimpses. The com- 
panion is of the ninth magnitude, some say the eighth, 
and the distance is about 9.5", angle of position (hereafter 
designated by p.) 199.* Its color is blue, in decided con- 

* The angle of position measures the inclination to the meridian of a line 
drawn between the principal star and its companion ; in other words, it shows in 
what direction from the primary we must look for the companion. It is reckoned 
from up to 360, beginning at the north point and passing around by east 
through south and west to north again. Thus, if the angle of position is or 
360, the companion is on the north side of the primary; if the angle is 90, the 
companion is to the east; if 180, to the south; if 270, to the west, and so for 
intermediate angles. It must be remembered, however, that in the field of the 
telescope the top is south and the bottom north, unless a prism is used, when 




MAP No. i. 



22 PLEASURES OF THE TELESCOPE 

trast with the white light of its great primary. Sir John 
Herschel, however, saw the companion red, as others have 
done. These differences are doubtless due to imperfec- 
tions of the eye or the telescope/" In 1871 Burnham be- 
lieved he had discovered that the companion was an ex- 
ceedingly close double star. No one except Burnham 
himself succeeded in dividing it, and he could only do so 
at times. Afterward, when he was at Mount Hamilton, 
he tried in vain to split it with the great thirty-six-inch 
telescope, in 1889, 1890, and 1891. His want of success 
induced him to suggest that the component stars were in 
rapid motion, and so, although he admitted that it might 
not be double after all, he advised that it should be 
watched for a few years longer. His confidence was justi- 
fied, for in 1898 Aitken, with the Lick telescope, saw and 
measured the distance of the extremely minute companion 
distance 0.17", p. 177. 

Rigel has been suspected of a slight degree of variabil- 
ity. It is evidently a star of enormous actual magnitude, 
for its parallax escapes trustworthy measurement. It 
can only be ranked among the very first of the light- 
givers of the visible universe. Spectroscopically it be- 
longs to a peculiar type which has very few representa- 
tives among the bright stars, and which has been thus 
described: " Spectra in which the hydrogen lines and the 
few metallic lines all appear to be of equal breadth and 
sharp definition." Rigel shows a line which some believe 
to represent magnesium; but while it has iron lines in its 
spectrum, it exhibits no evidence of the existence of any 
such cloud of volatilized iron as that which helps to en- 
velop the sun. 

directions become complicated. East and west can be readily identified by 
noticing the motion of a star through the field ; it moves toward the west and 
from the east. 



IN THE STARRY HEAVENS 23 

For another test of what the three-inch will do turn 
to ?, the lower, or left-hand, star in the Belt. This is a 
triple, the magnitudes being second, sixth, and tenth. 
The sixth-magnitude star is about 2.5" from the primary, 
p. 149, and has a very peculiar color, hard to describe. 
It requires careful focusing to get a satisfactory view of 
this star with a three-inch telescope. Use magnifying 
powers up to two hundred and fifty diameters. With our 
four-inch the star is much easier, and the five-inch show r s 
it readily with a power of one hundred. The tenth-magni- 
tude companion is distant 56", p. 8, and may be glimpsed 
with the three-inch. Upon the whole, we shall find that 
we get more pleasing views of f Orionis with the four- 
inch glass. 

Just to the left of f, and in the same field of view with 
a very low power, is a remarkable nebula bearing the 
catalogue number 1227. We must use our five-inch on 
this with a low power, but with ? out of the field in order 
to avoid its glare. The nebula is exceedingly faint, and 
we can be satisfied if we see it simply as a hazy spot, 
although with much larger telescopes it has appeared at 
least half a degree broad. Tempel saw several centers 
of condensation in it, and traced three or four broad nebu- 
lous streams, one of which decidedly suggested spiral 
motion. 

The upper star in the Belt, 8, is double; distance, 53", 
p. 360; magnitudes, second and seventh very nearly; 
colors, white and green or blue. This, of course, is an 
easy object for the three-inch with a low magnifying 
power. It Would be useless to look for the two fainter 
companions of S, discovered by Burnham, even with our 
five-inch glass. But we shall probably need the five-inch 
for our next attempt, and it will be well to put on a high 
power, say three hundred diameters. The star to be ex- 



24 PLEASURES OF THE TELESCOPE 

amined is the little brilliant dangling below the right- 
hand end of the Belt, toward Rigel. It appears on the 
map as TJ. Spare no pains in getting an accurate focus, 
for here is something worth looking at, and unless you 
have a trained eye you will not easily see it. The star is 
double, magnitudes third and sixth, and the distance from 
center to center barely exceeds 1", p. 87. A little tremu- 
lousness of the atmosphere for a moment conceals the 
smaller star, although its presence is manifest from the 
peculiar jutting of light on one side of the image of the 
primary. But in an instant the disturbing undulations 
pass, the air steadies, the image shrinks and sharpens, 
and two points of piercing brightness, almost touch- 
ing one another, dart into sight, the more brilliant one 
being surrounded by an evanescent circle, a tiny ripple of 
light, which, as it runs round the star and then recedes, 
alternately embraces and releases the smaller companion. 
The wash of the light-waves in the atmosphere provokes 
many expressions of impatience from the astronomer, but 
it is often a beautiful phenomenon nevertheless. 

Between rj and 3 is a fifth-magnitude double star, 2 725, 
which is worth a moment's attention. The primary, of a 
reddish color, has a very faint star, eleventh magnitude, 
at a distance of 12.7", p. 88. 

Still retaining the five-inch in use, we may next turn 
to the other end of the Belt, where, just under f, we per- 
ceive the fourth-magnitude star o-. He must be a person 
of indifferent mind who, after looking with unassisted 
eyes at the modest glimmering of this little star, can see 
it as the telescope reveals it without a thrill of wonder 
and a cry of pleasure. The glass, as by a touch of magic, 
changes it from one into eight or ten stars. There are 
two quadruple sets three and a half minutes of arc apart. 
The first set exhibits a variety of beautiful colors. The 



IN THE STARRY HEAVENS 25 

largest star, of fourth magnitude, is pale gray; the second 
in rank, seventh magnitude, distance 42", p. 61, presents 
a singular red, "grape-red" Webb calls it; the third, 
eighth magnitude, distance 12", p. 84, is blue; and the 
fourth, eleventh magnitude, distance 12", p. 236, is ap- 
parently white. Burnham has doubled the fourth-mag- 
nitude star, distance 0.23". The second group of four 
stars consists of three of the eighth to ninth magnitude, 
arranged in a minute triangle with a much fainter star 
near them. Between the two quadruple sets careful gaz- 
ing reveals two other very faint stars. While the five- 
inch gives a more satisfactory view of this wonderful mul- 
tiple star than any smaller telescope can do, the four-inch 
and even the three-inch would have shown it to us as a 
very beautiful object. However we look at them, there 
is an appearance of association among these stars, shin- 
ing with their contrasted colors and their various degrees 
of brilliance, which is significant of the diversity of con- 
ditions and circumstances under which the suns and 
worlds beyond the solar walk exist. 

From <r let us drop down to see the wonders of Orion's 
Sword displayed just beneath. We can use with advan- 
tage any one of our three telescopes; but since we are 
going to look at a nebula, it is fortunate that we have a 
glass so large as five inches aperture. It will reveal in- 
teresting things that escape the smaller instruments, be- 
cause it grasps more than one and a half times as much 
light as the four-inch, and nearly three times as much as 
the three-inch; and in dealing with nebula a plenty of 
light is the chief thing to be desired. The middle star in 
the Sword is 0, and is surrounded by the celebrated 
Nebula of Orion. The telescope shows separated into 
four stars arranged at the corners of an irregular square, 
and shining in a black gap in the nebula. These four 
3 



26 PLEASURES OF THE TELESCOPE 

stars are collectively named the Trapezium. The bright- 
est is of the sixth magnitude, the others are of the 
seventh, seven and a half, and eighth magnitudes respec- 
tively. The radiant mist about them has a faint green- 
ish tinge, while the four stars, together with three others 
at no great distance, which follow a fold of the nebula 
like a row of buttons on a coat, always appear to me to 
show an extraordinary liveliness of radiance, as if the 
strange haze served to set them off. 

Our three-inch would have shown the four stars of the 
Trapezium perfectly well, and the four-inch would have 
revealed a fifth star, very faint, outside a line joining the 

smallest of the four 
and its nearest neigh- 
bor. But the five- 
inch goes a step far- 
ther and enables us,, 
with steady gazing to 
see even a sixth star, 
of only the twelfth 
magnitude, just out- 

THE TRAPEZIUM WITH THE FIFTH AND SIXTH STARS. ^ ne * r ^P^ zlum > 

near the brightest 

member of the quartet. The Lick telescope has disclosed 
one or two other minute points of light associated with 
the Trapezium. But more interesting than the Trape- 
zium is the vast cloud, full of strange shapes, surrounding 
it. Nowhere else in the heavens is the architecture of 
a nebula so clearly displayed. It is an unfinished temple 
whose gigantic dimensions, while exalting the imagina- 
tion, proclaim the omnipotence of its builder. But 
though unfinished it is not abandoned. The work of crea- 
tion is proceeding within its precincts. There are stars 
apparently completed, shining like gems just dropped 




IN THE STAEBY HEAVENS 27 

from the hand of the polisher, and around them are 
masses, eddies, currents, and swirls of nebulous matter 
yet to be condensed, compacted, and constructed into 
suns. It is an education in the nebular theory of the 
universe merely to look at this spot with a good tele- 
scope. If we do not gaze at it long and wistfully, and 
return to it many times with unflagging interest, we may 
be certain that there is not the making of an astronomer 
in us. 

Before quitting the Orion nebula do not fail to notice 
an eighth-magnitude star, a short distance northeast of 
the Great Nebula, and nearly opposite the broad opening 
in the latter that leads in toward the gap occupied by the 
Trapezium. This star is plainly enveloped in nebulosity, 
that is unquestionably connected with the larger mass of 
which it appears to form a satellite. 

At the lower end of the Sword is the star *, somewhat 
under the third magnitude. Our three-inch will show 
that it has a bluish companion of seventh or eighth mag- 
nitude, at a little more than 11" distance, p. 142, and the 
larger apertures will reveal a third star, of tenth mag- 
nitude, and reddish in color, distance 49", p. 103. Close 
by i we find the little double star 2 747, whose compo- 
nents are of five and a half and six and a half magnitudes 
respectively, and separated 36", p. 223. Above the up- 
permost star in the Sword is a small star cluster, No. 
1184, which derives a special interest from the fact that it 
incloses a delicate double star, 2 750, whose larger com- 
ponent is of the sixth magnitude, while the smaller is of 
the ninth, and the distance is only 4.3", p. 59. We may 
try the four-inch on this object. 

Having looked at a (Betelgeuse), the great topaz star 
on Orion's right shoulder, and admired the splendor of its 
color, we may turn the four-inch upon the star 2 795, fre- 



28 PLEASURES OF THE TELESCOPE 

quently referred to by its number as " 52 Orionis." It con- 
sists of one star of the sixth and another of sixth and a 
half magnitude, only 1.5" apart, p. 200. Having sepa- 
rated them with a power of two hundred and fifty diame- 
ters on the four-inch, we may try them with a high power 
on the three-inch. We shall only succeed this time if 
our glass is of first-rate quality and the air is perfectly 
steady. 

The star X in Orion's head presents an easy conquest 
for the three-inch, as it consists of a light-yellow star of 
magnitude three and a half and a reddish companion of 
the sixth magnitude; distance 4", p. 43. There is also 
a twelfth-magnitude star at 27", p. 183, and a tenth or 
eleventh magnitude one at 149", p. 278. These are tests 
for the five-inch, and we must not be disappointed if we 
do not succeed in seeing the smaller one even with that 
aperture. 

Other objects in Orion, to be found with the aid of 
our map, are: 2 627, a double star, magnitude six and a 
half and seven, distance 21", p. 260; O 2 98, otherwise 
named i Orionis, double, magnitude six and seven, distance 
1", p. 180, requires five-inch glass; 2 652, double, magni- 
tudes six and a half and eight, distance 1.7", p. 184; p, 
double, magnitudes five and eight and a half, the latter 
blue, distance 7", p. 62, may be tried with a three-inch; T, 
triple star, magnitudes four, ten and a half, and eleven, 
distances 36", p. 249, and 36", p. 60. Burnham discov- 
ered that the ten-and-a-half magnitude star is again 
double, distance 4", p. 50. There is not much satisfac- 
tion in attempting T Orionis with telescopes of ordinary 
apertures; 2 Osfr, otherwise m Orionis, double, magnitudes 
five and a half (greenish) and seven, distance 31.7", p. 28, 
a pretty object; 2 728, otherwise A 32, double, magnitudes 
five and seven, distance, 0.5" or less, p. 206, a rapid 



IN THE STARRY HEAVENS 29 

binary,* which is at present too close for ordinary tele- 
scopes, although it was once within their reach; 2 729, 
double, magnitudes six and eight, distance 2", p. 26, the 
smaller star pale blue try it with a four-inch, but five- 
inch is better; 2 816, double, magnitudes six and half and 
eight and a half, distance 4", p. 289; ^2, double, magni- 
tudes five and a half and eleven, distance 3", or a little 
less, p. 322; 905, star cluster, contains about twenty 
stars from the eighth to the eleventh magnitude; 1267, 
nebula, faint, containing a triple star of the eighth magni- 
tude, two of whose components are 51" apart, while the 
third is only 1.7" from its companion, p. 85; 1376, star 
cluster, small and crowded; 1361, star cluster, triangular 
shape, containing thirty stars, seventh to tenth magni- 
tudes, one of which is a double, distance 2.4". 

Let us now leave the inviting star-fields of Orion and 
take a glance at the little constellation of Lepus, crouch- 
ing at the feet of the mythical giant. We may begin with 
a new kind of object, the celebrated red variable R Le- 
poris (map No. 1). This star varies from the sixth or 
seventh magnitude to magnitude eight and a half in a 
period of four hundred and twenty-four days. Hind's 
picturesque description of its color has frequently been 
quoted. He said it is " of the most intense crimson, re- 
sembling a blood-drop on the black ground of the sky." 
It is important to remember that this star is reddest when 
faintest, so that if we chance to see it near its maximum of 
brightness it will not impress us as being crimson at all, 
but rather a dull, coppery red. Its spectrum indicates 
that it is smothered with absorbing vapors, a sun near 
extinction which, at intervals, experiences an accession of 
energy and bursts through its stifling envelope with ex- 

* The term "binary" is used to describe double stars which are in motion 
about their common center of gravity. 



30 PLEASURES OF THE TELESCOPE 

plosive radiance, only to faint and sink once more. It is 
well to use our largest aperture in examining this star. 

We may also employ the. five-inch for an inspection of 
the double star i, whose chief component of the fifth mag- 
nitude is beautifully tinged with green. The smaller 
companion is very faint, eleventh magnitude, and the dis- 
tance is about 13", p. 337. 

Another fine double in Lepus is *, to be found just 
below *; the components are of the fifth and eighth mag- 
nitudes, pale yellow and blue respectively, distance 2.5", 
p. 360; the third-magnitude star a has a tenth-magnitude 
companion at a distance of 35", p. 156, and its neighbor ft 
(map No. 2), according to Burnham, is attended' by three 
eleventh-magnitude stars, two of which are at distances 
of 206", p. 75, and 240", p. 58, respectively, while the 
third is less than 3" from 0, p. 288 ; the star 7 (map No. 2) 
is a wide double, the distance being 94", and the magni- 
tudes four and eight. The star numbered 45 is a remark- 
able multiple, but the components are too faint to possess 
much interest for those who are not armed with very pow- 
erful telescopes. 

From Lepus we pass to Canis Major (map No. 2). 
There is no hope of our being able to see the companion 
of a (Sirius), at present (1901), even with our five-inch. 
Discovered by Alvan Clark with an eighteen-inch tele- 
scope in 1862, when its distance was 10" from the center 
of Sirius, this ninth-magnitude star has since been swal- 
lowed up in the blaze of its great primary. At first, it 
slightly increased its distance, and from 1868 until 1879 
most of the measures made by different observers con- 
siderably exceeded 11". Then it began to close up, and in 
1890 the distance scarcely exceeded 4". Burnham was 
the last to catch sight of it with the Lick telescope in that 
year. After that no human eye saw it until 1896, when it 



32 PLEASURES OF THE TELESCOPE 

was rediscovered at the Lick Observatory. Since then 
the distance has gradually increased to nearly 5". Ac- 
cording to Burnham, its periodic time is about fifty-three 
years, and its nearest approach to Sirius should have 
taken place in the middle of 1892. Later calculations 
reduce the periodic time to forty-eight or forty-nine years. 
If we can not see the companion of the Dog Star with our 
instruments, we can at least, while admiring the splendor 
of that dazzling orb, reflect with profit upon the fact that 
although the companion is ten thousand times less bright 
than Sirius, it is half as massive as its brilliant neighbor. 
Imagine a subluminous body half as ponderous as the sun 
to be set revolving round it somewhere between Uranus 
and Neptune. Remember that that body would possess 
one hundred and sixty-five thousand times the gravitating 
energy of the earth, and that five hundred and twenty 
Jupiters would be required to equal its power of attrac- 
tion, and then consider the consequences to our easy-going 
planets! Plainly the solar system is not cut according to 
the Sirian fashion. We shall hardly find a more remark- 
able coupling of celestial bodies until we come, on another 
evening, to a star that began, ages ago, to amaze the 
thoughtful and inspire the superstitious with dread the 
wonderful Algol in Perseus. 

We may remark in passing that Sirius is the brightest 
representative of the great spectroscopic type I, which 
includes more than half of all the stars yet studied, and 
which is characterized by a white or bluish-white color, 
and a spectrum possessing few or at best faint metallic 
lines, but remarkably broad, black, and intense lines of 
hydrogen. The inference is that Sirius is surrounded by 
an enormous atmosphere of hydrogen, and that the in- 
tensity of its radiation is greater, surface for surface, 
than that of the sun. There is historical evidence to sup- 



/A^ THE STARRY HEAVENS 33 

port the assertion, improbable in itself, that Sirius, with- 
in eighteen hundred years, has changed color from red 
to white. 

With either of our telescopes we shall have a feast for 
the eye when we turn the glass upon the star cluster 
No. 1454, some four degrees south of Sirius. Look for a 
red star near the center. Observe the curving rows so 
suggestive of design, or rather of the process by which 
this cluster was evolved out of a pre-existing nebula. You 
will recall the winding streams in the Great Nebula of 
Orion. Another star cluster worth a moment's attention 
is No. 1479, above and to the left of Sirius. We had bet- 
ter use the five-inch for this, as many of the stars are very 
faint. Not far away we find the double star p, whose 
components are of the fifth and eighth magnitudes, dis- 
tance 2.8", p. 343. The small star is pale blue. Cluster 
No. 1512 is a pleasing object with our largest aperture. 
In No. 1511 we have a faint nebula remarkable for the 
rows of minute stars in and near it. The star 7 is an 
irregular variable. In 1670 it is said to have almost dis- 
appeared, while at the beginning of the eighteenth cen- 
tury it was more than twice as bright as it is to-day. The 
reddish star 8 is also probably variable. In my " Astron- 
omy with an Opera Glass " will be found a cut showing 
a singular array of small stars partly encircling S. These 
are widely scattered by a telescope, even with the lowest 
power. 

Eastward from Canis Major we find some of the stars 
of Argo Navis. 2 1097, of the sixth magnitude, has two 
minute companions at 20" distance, p. 311 and 312. 
The large star is itself double, but the distance, 0.8", 
p. 166, places it beyond our reach. According to Burn- 
ham, there is yet a fourth faint star at 31", p. 40. Some 
three degrees and a half below and to the left of the star 



IN THE STARRY HEAVENS 35 

just examined is a beautiful star cluster, No. 1551. Nos. 
1564, 1571, and 1630 are other star clusters well worth 
examination. A planetary nebula is included in 1564. 
With very powerful telescopes this nebula has been seen 
ring-shaped. 2 1146, otherwise known as 5 Navis, is a 
pretty double, colors pale yellow and blue, magnitudes 
five and seven, distance 3.25", p. 19. Our three-inch will 
suffice for this. 

North of Canis Major and Argo we find Monoceros and 
Canis Minor (map No. 3). The stars forming the western 
end of Monoceros are depicted on map No. 1. We shall 
begin with these. The most interesting and beautiful is 
11, a fine triple star, magnitudes five, six, and seven, 
distances 7.4", p. 131, and 2.7", p. 103. Sir William Her- 
schel regarded this as one of the most beautiful sights in 
the heavens. It is a good object to try our three-inch on, 
although it should not be difficult for such an aperture. 
The star 4 is also a triple, magnitudes six, ten, and eleven, 
distances 3.4", p. 178, and 10", p. 244. We should glance 
at the star 5 to admire its fine orange color. In 8 we find 
a golden fifth-magnitude star, combined with a blue or 
lilac star of the seventh magnitude, distance 14", p. 24. 
2 938 is a difficult double, magnitudes six and a half and 
twelve, distance 10", p. 210. 2 921 is double, magnitudes 
six and a half and eight, distance 16", p. 4. At the spot 
marked on the map 1424 we find an interesting cluster 
containing one star of the sixth magnitude. 

The remaining stars of Monoceros will be found on 
map No. 3. The double and triple stars to be noted are S, 
or 2 950 (which is also a variable and involved in a faint 
nebula), magnitudes six and nine, distance 2.5", p. 206; 
21183, double, magnitudes five and a half and eight, dis- 
tance 31", p. 326; 2 1190, triple, magnitudes five and a 
half, ten, and nine, distances 31", p. 105, and 67", p. 244. 



36 PLEASURES OF THE TELESCOPE 

The clusters are 1465, which has a minute triple star near 
the center; 1483, one member of whose swarm is red; 
1611, very small but rich; and 1637, interesting for the 
great number of ninth-magnitude tars that it contains. 
We should use the five-inch for all of these. 

Canis Minor and the Head of Hydra are also contained 
on map No. 3. Procyon, a of Canis Minor, has several mi- 
nute stars in the same field of view. There is, besides, a 
companion which, although it was known to exist, no tele- 
scope was able to detect until November, 1896. It must be 

of immense mass, since 
its attraction causes 
perceptible perturba- 
tions in the motion of 
Procyon. Its magni- 
tude is eight and a 
half, distance 4.83", p. 
338. One of the small 
stars just referred to, 
the second one east of 
Procyon, distant one 
third of the moon's di- 
ameter, is an interest- 

PROCYON AND ITS NEIGHBORS. 

ing double. Our four- 
inch may separate it, and the five-inch is certain to do so. 
The magnitudes are seven and seven and a half or eight, 
distance 1.2", p. 133. This star is variously named 2 1126 
and 31 Can. Min. Bode. Star No. 14 is a wide triple, mag- 
nitudes six, seven, and eight, distances 75, p. 65, and 115", 
p. 154. 

In the Head of Hydra we find 2 1245, a double of the 
sixth and seventh magnitudes, distance 10.5", p. 25. The 
larger star shows a fine yellow. In e we have a beautiful 
combination of a yellow with a blue star, magnitudes four 




IN THE STARRY HEAVENS 37 

and eight, distance 3.4", p. 198. Finally, let us look at 
for a light test with the five-inch. The two stars com- 
posing it are of the fourth and twelfth magnitudes, dis- 
tance 50", p. 170. 

The brilliant constellations of Gemini and Taurus 
tempt us next, but warning clouds are gathering, and we 
shall do well to house our telescopes and warm our fingers 
by the winter fire. There will be other bright nights, and 
the stars are lasting. 



CHAPTER III 

FROM GEMINI TO LEO AND ROUND ABOUT 

"If thou wouldst gaze on starry Charioteer, 
And hast heard legends of the wondrous Goat, 
Vast looming shalt thou find on the Twins' left, 
His form bowed forward." POSTE'S ARATUS. 

THE zodiacal constellations of Gemini, Cancer, and 
Leo, together with their neighbors Auriga, the Lynx, 
Hydra, Sextans, and Coma Berenices, will furnish an 
abundance of occupation for our second night at the tele- 
scope. We shall begin, using our three-inch glass, with a, 
the chief star of Gemini (map No. 4). This is ordinarily 
known as Castor. Even an inexperienced eye perceives 
at once that it is not as bright as its neighbor Pollux, P. 
Whether this fact is to be regarded as indicating that 
Castor was brighter than Pollux in 1603, when Bayer at- 
tached their Greek letters, is still an unsettled question. 
Castor may or may not be a variable,, but it is, at any rate, 
one of the most beautiful double stars in the heavens. A 
power of one hundred is amply sufficient to separate its 
components, whose magnitudes are about two and three, 
the distance between them being 6", p. 226. A slight 
yet distinct tinge of green, recalling that of the Orion 
nebula, gives a peculiar appearance to this couple. Green 
is one of the rarest colors among the stars. Castor be- 
longs to the same general spectroscopic type in which 
Sirius is found, but its lines of hydrogen are broader than 
those seen in the spectrum of the Dog Star. There is 

38 



40 PLEASURES OF THE TELESCOPE 

reason for thinking that it may be surrounded with a 
more extensive atmosphere of that gaseous metal called 
hydrogen than any other bright star possesses. There 
seems to be no doubt that the components of Castor are 
in revolution around their common center of gravity, 
although the period is uncertain, varying in different esti- 
mates all the way from two hundred and fifty to one thou- 
sand years; the longer estimate is probably not far from 
the truth. There is a tenth-magnitude star, distance 73", 
p. 164, which may belong to the same system. 

From Castor let us turn to Pollux, at the same time 
exchanging our three-inch telescope for the four-inch, or, 
still better, the five-inch. Pollux has five faint compan- 
ions, of which we may expect to see three, as follows: 
Tenth magnitude, distance 175", p. 70; nine and a half 
magnitude, distance 206", p. 90, and ninth magnitude, 
distance 229", p. 75. Burnham has seen a star of thir- 
teen and a half magnitude, distance 43", p. 275, and has 
divided the tenth-magnitude star into two components, 
only 1.4" apart, the smaller being of the thirteenth mag- 
nitude, and situated at the angle 128. A calculation 
based on Dr. Elkin's parallax of 0.068" for Pollux shows 
that that star may be a hundredfold more luminous than 
the sun, while its nearest companion may be a body 
smaller than our planet Jupiter, but shining, of course, by 
its own light. Its distance from Pollux, however, exceeds 
that of Jupiter from the sun in the ratio of about one hun- 
dred and thirty to one. 

In the double star IT we shall find a good light test for 
our three-inch aperture, the magnitudes being six and 
eleven, distance 22", p. 212. The four-inch will show 
that K is a double, magnitudes four and ten, distance 6", 
p. 232. The smaller star is of a delicate blue color, and 
it has been suspected of variability. That it may be vari- 



FROM GEMINI TO LEO AND HOUND ABOUT 41 

able is rendered the more probable by the fact that in the 
immediate neighborhood of K there are three undoubted 
variables, S, T, and U, and there appears to be some mys- 
terious law of association which causes such stars to 
group themselves in certain regions. None of the vari- 
ables just named ever become visible to the naked eye, 
although they all undergo great changes of brightness, 
sinking from the eighth or ninth magnitude down to the 
thirteenth or even lower. The variable R, which lies con- 
siderably farther west, is well worth attention because of 
the remarkable change of color which it sometimes ex- 
hibits. It has been seen blue, red, and yellow in succes- 
sion. It varies from between the sixth and seventh mag- 
nitudes to less than the thirteenth in a period of about 
two hundred and forty-two days. 

Not far away we find a still more curious variable f; 
this is also an interesting triple star, its principal compo- 
nent being a little under the third magnitude, while one 
of the companions is of the seventh magnitude, distance 
90", p. 355, and the other is of the eleventh magnitude or 
less, distance 65", p. 85. We should hardly expect to see 
the fainter companion with the three-inch. The principal 
star varies from magnitude three and seven tenths down 
to magnitude four and a half in a period 
of a little more than ten days. 

With the four- or five-inch we get a 
very pretty sight in 8, which appears split 
into a yellow and a purple star, magni- 
tudes three and eight, distance 7", p. 206. 

Near S, toward the east, lies One Of WONDERFUL NEBULA IN 

GEMINI (1532). 

the strangest of all the nebula. (See 
the figures 1532 on the map.) Our telescopes will show 
it to us only as a minute star surrounded with a nebu- 
lous atmosphere, but its appearance with instruments- 




42 PLEASURES OF THE TELESCOPE 

of the first magnitude is so astonishing and at the same 
time so beautiful that I can not refrain from giving 
a brief description of it as I saw. it in 1893 with the 
great Lick telescope. In the center glittered the star, 
and spread evenly around it was a circular nebulous disk, 
pale yet sparkling and conspicuous. This disk was sharp- 
ly bordered by a narrow black ring, and outside the ring 
the luminous haze of the nebula again appeared, gradu- 
ally fading toward the edge to invisibility. The accom- 
panying cut, which exaggerates the brightness of the 
nebula as compared with the star, gives but a faint idea 
of this most singular object. If its peculiarities were 
within the reach of ordinary telescopes, there are few 
scenes in the heavens that would be deemed equally ad- 
mirable. 

In the star rj we have another long-period variable, 
which is also a double star; unfortunately the companion, 
being of only the tenth magnitude and distant less than 1" 
from its third-magnitude primary, is beyond the reach of 
our telescopes. But y points the way to one of the finest 
star clusters in the sky, marked 1360 on the map. The 
naked eye perceives that there is something remarkable 
in that place, and the opera glass faintly reveals its dis- 
tant splendors, but the telescope fairly carries us into its 
presence. Its stars are innumerable, varying from the 
ninth magnitude downward to the last limit of visibility, 
and presenting a wonderful array of curves which are 
highly interesting from the point of view of the nebular 
origin of such clusters. Looking backward in time, with 
that theory to guide us, we can see spiral lines of nebulous 
mist occupying the space that now glitters with inter- 
lacing rows of stars. It is certainly difficult to under- 
stand how such lines of nebula could become knotted with 
the nuclei of future stars, and then gradually be absorbed 



FROM GEMINI TO LEO AND ROUND ABOUT 43 

into those stars; and yet, if such a process does not occur, 
what is the meaning of that narrow nebulous streak in 
the Pleiades along which five or six stars are strung like 
beads on a string? The surroundings of this cluster, 
1360, as one sweeps over them with the telescope gradu- 
ally drawing toward the nucleus, have often reminded me 
of the approaches to such a city as London. Thicker and 
closer the twinkling points become, until at last, as the 
observer's eye follows the gorgeous lines of stars trend- 
ing inward, he seems to be entering the streets of a bril- 
.liantly lighted metropolis. 

Other objects in Gemini that we can ill miss are: A 6 , 
double, magnitudes three and eleven, distance 73", p. 76, 
colors yellow and blue; 15, double, magnitudes six and 
eight, distance 33", p. 205; 7, remarkable for array of 
small stars near it; 38, double, magnitudes six and eight, 
distance 6.5", p. 162, colors yellow and blue (very pretty); 
X, double, magnitudes four and eleven, distance 10", p. 30, 
color of larger star blue try with the five-inch; e, double, 
magnitudes three and nine, distance 110", p. 94. 

From Gemini we pass to Cancer. This constellation 
has no large stars, but its great cluster Praesepe (1681 on 
map No. 4) is easily seen as a starry cloud with the naked 
eye. With the telescope it presents the most brilliant ap- 
pearance with a very low power. It was one of the first 
objects that Galileo turned to when he had completed his 
telescope, and he wonderingly counted its stars, of which 
he enumerated thirty-six, and made a diagram showing 
their positions. 

The most interesting star in Cancer is , a celebrated 
triple. The magnitudes of its components are six, seven, 
and seven and a half; distances 1.14", p. 6, and 5.7", p. 
114. We must use our five-inch glass in order satisfac- 
torily to separate the two nearest stars. The gravita- 



44 PLEASURES OF THE TELESCOPE 

tional relationship of the three stars is very peculiar. 
The nearest pair revolve around their common center in 
about fifty-eight years, while the third star revolves with 
the other two, around a center common to all three, in a 
period of six or seven hundred years. But the movements 
of the third star are erratic, and inexplicable except upon 
the hypothesis advanced by Seeliger, that there is an in- 
visible, or dark, star near it by whose attraction its mo- 
tion is perturbed. 

In endeavoring to picture the condition of things in f 
Cancri we might imagine our sun to have a companion sun, 
a half or a third as large as itself, and situated within what 
may be called planetary distance, circling with it around 
their center of gravity; while a third sun, smaller than 
the second and several times as far away, and accom- 
panied by a black or non-luminous orb, swings with the 
first two around another center of motion. There you 
would have an entertaining complication for the inhabit- 
ants of a system of planets! 

Other objects in Cancer are: 2 1223, double star, mag- 
nitudes six and six and a half, distance 5", p. 214; 2 1291, 
double, magnitudes both six, distance 1.3", p. 328 four- 
inch should split it; *, double, magnitudes four and a half 
and six and a half, distance 30", p. 308 ; 66, double magni- 
tudes six and nine, distance 4.8", p. 136; 21311, double, 
magnitudes both about the seventh, distance 7", p. 200 ; 
1712, star cluster, very beautiful with the five-inch glass. 

The constellation of Auriga may next command our 
attention (map No. 5). The calm beauty of its leading 
star Capella awakens an admiration that is not dimin- 
ished by the rivalry of Orion's brilliants glittering to the 
south of it. Although Capella must be an enormously 
greater sun than ours, its spectrum bears so much resem- 
blance to the solar spectrum that a further likeness of 



46 PLEASURES OF THE TELESCOPE 

condition is suggested. No close telescopic companion to 
Capella has been discovered. A ninth-magnitude com- 
panion, distant 159", p. 146, and two others, one of 
twelfth magnitude at 78", p. 317, and the other of thir- 
teenth magnitude at 126", p. 183, may be distant satel- 
lites of the great star, but not planets in the ordinary 
sense, since it is evident that they are self-luminous. 
It is a significant fact that most of the first-magnitude 
stars have faint companions which are not so distant 
as altogether to preclude the idea of- physical relation- 
ship. 

But while Capella has no visible companion, Campbell, 
of the Lick Observatory, has lately discovered that it is a 
conspicuous example of a peculiar class of binary stars 
only detected within the closing decade of the nineteenth 
century. The nature of these stars, called spectroscopic 
binaries, may perhaps best be described while we turn 
our attention from Capella to the second star in Auriga 
(Menkalina), which not only belongs to the same class, 
but was the first to be discovered. Neither our tele- 
scopes, nor any telescope in existence, can directly reveal 
the duplicity of fi Auriga to the eye i. e., we can not 
see the two stars composing it, because they are so 
close that their light remains inextricably mingled after 
the highest practicable magnifying power has been ap- 
plied in the effort to separate them. But the spectro- 
scope shows that the star is double and that its compo- 
nents are in rapid revolution around one another, com- 
pleting their orbital swing in the astonishingly short 
period of four days! The combined mass of the two stars 
is estimated to be two and a half times the mass of the 
sun, and the distance between them, from center to center, 
is about eight million miles. 

The manner in which the spectroscope revealed the 



FROM GEMINI TO LEO AND ROUND ABOUT 47 

existence of two stars in /9 Auriga? is a beautiful illustra- 
tion of the unexpected and, so to speak, automatic appli- 
cation of an old principle in the discovery of new facts 
not looked for. It was noticed at the Harvard Observa- 
tory that the lines in the photographed spectrum of /Q 
Auriga? (and of a few other stars to be mentioned later) 
appeared single in some of the photographs and double 
in others. Investigation proved that the lines were 
doubled at regular intervals of about two days, and that 
they appeared single in the interim. The explanation 
was not far to seek. It is known that all stars which are 
approaching us have their spectral lines shifted, by virtue 
of their motion of approach, toward the violet end of the 
spectrum, and that, for a similar reason, all stars which 
are receding have their lines shifted toward the red end 
of the spectrum. Now, suppose two stars to be revolving 
around one another in a plane horizontal, or nearly so, to 
the line of sight. When they are at their greatest angu- 
lar distance apart as seen from the earth one of them 
will evidently be approaching at the same moment that 
the other is receding. The spectral lines of the first will 
therefore be shifted toward the violet, and those of the 
second will be shifted toward the red. Then if the stars, 
when at their greatest distance apart, are still so close 
that the telescope can not separate them, their light will 
be combined in the spectrum; but the spectral lines, being 
simultaneously shifted in opposite directions, will neces- 
sarily appear to be doubled. As the revolution of the 
stars continues, however, it is clear that their motion will 
soon cease to be performed in the line of sight, and will 
become more and more athwart that line, and as this oc- 
curs the spectral lines will gradually assume their normal 
position and appear single. This is the sequence of phe- 
nomena in /3 Auriga?. And the same sequence is found in 



48 PLEASURES OF THE TELESCOPE 

Capella and in several other more or less conspicuous 
stars in various parts of the heavens. 

Such facts, like those connecting rows and groups of 
stars with masses and spiral lines of -nebula are obscure 
signboards, indicating the opening of a way which, start- 
ing in an unexpected direction, leads deep into the mys- 
teries of the universe. 

Southward from $ we find the star 0, which is a beauti- 
ful quadruple. We shall do best with our five-inch here, 
although in a fine condition of the atmosphere the four- 
inch might suffice. The primary is of the third magni- 
tude; the first companion is of magnitude seven and a 
half, distance 2", p. 5; the second, of the tenth magni- 
tude, distance 45", p. 292; and the third, of the tenth 
magnitude, distance 125", p. 350. 

We should look at the double 2 616 with one of our 
larger apertures in order to determine for ourselves what 
the colors of the components are. There is considerable 
diversity of opinion on this point. Some say the larger 
star is pale red and the smaller light blue; others con- 
sider the color of the larger star to be greenish, and some 
have even called it white. The magnitudes are five and 
nine, distance 6", p. 350. . 

Auriga contains several noteworthy clusters which 
will be found on the map. The most beautiful of these is 
1295, in which about five hundred stars have been counted. 

The position of the new star of 1892, known as Nova 
Aurigse, is also indicated on the map. While this never 
made a brilliant appearance, it gave rise to a greater va- 
riety of speculative theories than any previous phenome- 
non of the kind. Although not recognized until January 
24, 1892, this star, as photographic records prove, was in 
existence on December 9, 1891. At its brightest it barely 
exceeded magnitude four and a half, and its maximum 



FROM GEMINI TO LEO AND ROUND ABOUT 49 

occurred within ten days after its first recognition. 
When discovered it was of the fifth magnitude. It was 
last seen in its original form with the Lick telescope on 
April 26th, when it had sunk to the lowest limit of visibil- 
ity. To everybody's astonishment it reappeared in the 
following August, and on the 17th of that month was seen 
shining with the light of a tenth-magnitude star, but pre- 
senting the spectrum of a nebula! Its visual appearance in 
the great telescope was now also that of a planetary 
nebula. Its spectrum during the first period of its visi- 
bility had been carefully studied, so that the means ex- 
isted for making a spectroscopic comparison of the phe- 
nomenon in its two phases. During the first period, when 
only a stellar spectrum was noticed, remarkable shiftings 
of the spectral lines occurred, indicating that two and 
perhaps three bodies were concerned in the production of 
the light of the new star, one of which was approaching 
the earth, while the other or the others receded with ve- 
locities of several hundred miles per second! On the 
revival in the form of a planetary nebula, while the char- 
acter of the spectrum had entirely changed, evidences of 
rapid motion in the line of sight remained. 

But what was the meaning of all this? Evidently a 
catastrophe of some kind had occurred out there in space. 
The idea of a collision involving the transformation of 
the energy of motion into that of light and heat suggests 
itself at once. But what were the circumstances of 
the collision? Did an extinguished sun, flying blindly 
through space, plunge into a vast cloud of meteoric parti- 
cles, and, under the lashing impact of so many myriads of 
missiles, break into superficial incandescence, while the 
cosmical wrack through which it had driven remained 
glowing with nebulous luminosity? Such an explanation 
has been offered by Seeliger. Or was Vogel right when 



50 PLEASURES OF THE TELESCOPE 

he suggested that Nova Auriga? could be accounted for by 
supposing that a wandering dark body had run into colli- 
sion with a system of planets surrounding a decrepit sun 
(and therefore it is to be "hoped uninhabited), and that 
those planets had been reduced to vapor and sent spin- 
ning by the encounter, the second outburst of light being 
caused by an outlying planet of the system falling a prey 
to the vagabond destroyer? Or some may prefer the ex- 
planation, based on a theory of Wilsing's, that two great 
bodies, partially or wholly opaque and nonluminous at 
their surfaces, but liquid hot within, approached one an- 
other so closely that the tremendous strain of their tidal 
attraction burst their shells asunder so that their bowels 
of fire gushed briefly visible, amid a blaze of spouting 
vapors. And yet Lockyer thinks that there was no solid 
or semisolid mass concerned in the phenomenon at all, but 
that what occurred was simply the clash of two immense 
swarms of meteors that had crossed one another's track. 

Well, where nobody positively knows, everybody has 
free choice. In the meantime, look at the spot in the 
sky where that little star made its appearance and under- 
went its marvelous transformation, for, even if you can 
see no remains of it there, you will feel your interest in 
the problem it has presented, and in the whole subject of 
astronomy, greatly heightened and vivified, as the visitor 
to the field of Waterloo becomes a lover of history on 
the spot. 

The remaining objects of special interest in Auriga 
may be briefly mentioned: 26, triple star, magnitudes five, 
eight, and eleven, distances 12", p. 268, and 26", p. 113; 
14, triple star, magnitudes five, seven and a half, and 
eleven, distances 14", p. 224, and 12.6", p. 342, the last 
difficult for moderate apertures; X, double, magnitudes 
five and nine, distance 121", p. 13; e, variable, generally 



FROM GEMINI TO LEO AND HOUND ABOUT 51 



of third magnitude, but has been seen of only four and 
a half magnitude; 41, double, magnitudes five and six, 
distance 8", p. 354; 996, 1067, 1119, and 1166, clusters all 
well worth inspection, 1119 being especially beautiful. 

The inconspicuous Lynx furnishes some fine telescopic 
objects, all grouped near the northwestern corner of the 
constellation. Without a six-inch telescope it would be a 
waste of time to attack the double star 4, whose compo- 
nents are of sixth and eighth magnitudes, distance 0.8", 
p. 103; but its neighbor, 5, a fine triple, is within our 
reach, the magnitudes being six, ten, and eight, distances 
30", p. 139, and 96", p. 272. In 12 Lyncis we find one of 
the most attractive of triple stars, which in good seeing 
weather is not beyond the powers of a three-inch glass, 
although we shall have a far more satisfactory view of it 
with the four-inch. The components are of the sixth, 
seventh, and eighth magnitudes, distances 1.4", p. 117, 
and 8.7", p. 304. A magnifying power which just suffices 
clearly to separate the disks of the two nearer stars 
makes this a fine sight. A beautiful contrast of colors 
belongs to the double star 14, but unfortunately the star 
is at present very close, the distance between its sixth and 
seventh magnitude components not exceeding 0.8", posi- 
tion angle 64. 2 958 is a pretty double, both stars being 
of the sixth magnitude, distance 5", p. 257. Still finer 
is 2 1009, a double, whose stars are both a little above the 
seventh magnitude and nearly equal, distance 3", p. 156. 
A low power suffices to show the three stars in 19, their 
magnitudes being six and a half, seven and a half, and 
eight, distances 15", p. 312, and 215", p. 358. Webb de- 
scribes the two smaller stars as plum-colored. Plum-col- 
ored suns! 

At the opposite end of the constellation are two fine 
doubles, 2 1333, magnitudes six and a half and seven, dis- 



52 PLEASURES OF THE TELESCOPE 

tance 1.4", p. 39; and 38, magnitudes four and seven, dis- 
tance 2.9", p. 235. 

Under the guidance of map No. 6 we turn to Leo, which 
contains one of the leading gems anjbng the double stars, 
7, whose components, of the second and fourth magnitudes, 
are respectively yellow and green, the green star, accord- 
ing to some observers, having a peculiar tinge of red. 
Their distance apart is 3.7", p. 118, and they are un- 
doubtedly in revolution about a common center, the prob- 
able period being about four hundred years. The three- 
inch glass should separate them easily when the air is 
steady, and a pleasing sight they are. 

The star i is a closer double, and also very pretty, mag- 
nitudes four and eight, colors lemon and light blue, dis- 
tance 2.17", p. 53. Other doubles are T, magnitudes five 
and seven, distance 95", p. 170; 88, magnitudes seven and 
nine, distance 15", p. 320; 90, triple, magnitudes six, 
seven and a half, and ten, distance, 3.5", p. 209, and 59", 
p. 234; 54, magnitudes four and a half and seven, dis- 
tance 6.2", p. 102; and 49, magnitudes six and nine, dis- 
tance 2.4", p. 158. 

Leo contains a remarkable variable star, K, deep red 
in color, and varying in a space of a hundred and forty- 
four days from the fifth to the tenth magnitude. It has 
also several nebulae, of which only one needs special men- 
tion, No. 1861. This is spindle-shaped, and large tele- 
scopes show that it consists of three nebula?. The ob- 
server with ordinary instruments finds little to see and 
little to interest him in these small, faint nebulae. 

We may just glance at two double stars in the small 
constellation of Sextans, situated under Leo. These are: 
9, magnitudes seven and eight, distance 53", p. 292; and 
35, magnitudes six and seven, distance 6.9", p. 240. 

Coma Berenices (map No. 6) includes several interest- 



54 PLEASURES OF THE TELESCOPE 

ing objects. Let us begin with the star 2, a double, of 
magnitudes six and seven and a half, distance 3.6", p. 240. 
The color of the smaller s^tar is lilac. This hue, although 
not extremely uncommon among ; double stars elsewhere, 
recurs again and again, with singular persistence, in this 
little constellation. For instance, in the very next star 
that we look at, 12, we find a double whose smaller com- 
ponent is lilac. The magnitudes in 12 are five and eight, 
distance 66", p. 168. So also the wide double 17, magni- 
tudes five and a half and six, distance 145", exhibits a 
tinge of lilac in the smaller component; the triple 35, mag- 
nitudes five, eight, and nine, distances 1", p. 77, and 
28.7", p. 124, has for colors yellow, lilac, and blue, and the 
double 24, magnitudes five and six, distance 20", p. 270, 
combines an orange with a lilac star, a very striking and 
beautiful contrast. We should make a mistake if we 
regarded this wonderful distribution of color among the 
double stars as accidental. It is manifestly expressive of 
their physical condition, although we can not yet decipher 
its exact meaning. 

The binary 42 Coma? Berenicis is too close for ordinary 
telescopes, but it is highly interesting as an intermediate 
between those pairs which the telescope is able to sepa- 
rate and those like ft Aurigse which no magnifying 
power can divide, but which reveal the fact that they are 
double by the periodical splitting of their spectral lines. 
The orbit in 42 Comae Berenicis is a very small one, so that 
even when the components are at their greatest distance 
apart they can not be separated by a five- or six-inch glass. 
Burnham, using the Lick telescope, in 1890 made the dis- 
tance 0.7"; Hall, using the Washington telescope, in 1891 
made it a trifle more than 0.5". He had measured it in 
1886 as only 0.27". The period of revolution is believed 
to be about twenty-five years. 



56 PLEASURES OF THE TELESCOPE 

In Coma Berenices there is an outlying field of the mar- 
velous nebulous region of Virgo, which we may explore 
on some future evening. .But the . nebulae in Coma are 
very faint, and, for an amateur, hardly worth the trouble 
required to pick them up. The two clusters included in 
the map, 2752 and 3453, are bright enough to repay inspec- 
tion with our largest aperture. 

Although Hydra is the largest constellation in the 
heavens, extending about seven hours, or 105, in right 
ascension, it contains comparatively few objects of inter 
est, and most of these are in the head or western end of 
the constellation, which we examined during our first 
night at the telescope. In the central portion of Hydra, 
represented on map No. 7, we find its leading star a, some- 
times called Alphard, or Cor Hydra?, a bright second-mag- 
nitude star that has been suspected of variability. It has 
a decided orange tint, and is accompanied, at a distance 
of 281", p. 153, by a greenish tenth-magnitude star. Bu. 
339 is a fine double, magnitudes eight and nine and a half, 
distance 1.3", p. 216. The planetary nebula 2102 is about 
V in diameter, pale blue in color, and worth looking at, 
because it is brighter than most objects of its class. Tern- 
pel and Secchi have given wonderful descriptions of it, 
both finding multitudes of stars intermingled with nebu- 
lous matter. 

For a last glimpse at celestial splendors for the night, 
let us turn to the rich cluster 1630, in Argo, just above the 
place where the stream of the Milky Way here bright in 
mid-channel and shallowing toward the shores separates 
into two or three currents before disappearing behind the 
horizon. It is by no means as brilliant as some of the 
star clusters we have seen, but it gains in beauty and im- 
pressiveness from the presence of one bright star that 
seems to captain a host of inferior luminaries. 



CHAPTER IV 

VIRGO AND HER NEIGHBORS 

..." that region 
Where still by night is seen 
The Virgin goddess near to bright Bo6tes." POSTE'S ARATUS. 

FOLLOWING the order of right ascension, we come next 
to the little constellations Crater and Corvus, which may 
be described as standing on the curves of Hydra (map 
No. 8). Beginning with Crater, let us look first at a, a 
yellow fourth-magnitude star, near which is a celebrated 
red variable R. With a low power w r e can see both a and 
R in the same field of view, like a very wide double. 
There is a third star of ninth magnitude, and bluish in 
color, near R on the side toward a. R is variable both in 
color and light. When reddest, it has been described as 
"scarlet," "crimson," and "blood-colored"; when palest, 
it is a deep orange-red. Its light variation has a period 
the precise length of which is not yet known. The cycle 
of change is included between the eighth and ninth mag- 
nitudes. 

While our three-inch telescope suffices to show R, it is 
better to use the five-inch, because of the faintness of the 
star. When the color is well seen, the contrast with a is 
very pleasing. 

There is hardly anything else in Crater to interest us, 
and we pass over the border into Corvus, and go at once 
to its chief attraction, the star 8. The components of this 
5 57 



VIRGO AND HER NEIGHBORS 59 

beautiful double are of magnitudes three and eight; dis- 
tance 24", p. 211; colors yellow and purple. 

The night being dark and clear, we take the five-inch 
and turn it on the nebula 3128, which the map shows just 
under the border of Corvus in the edge of Hydra. Her- 
schel believed he had resolved this into stars. It is a 
faint object and small, not exceeding one eighth of the 
moon's diameter. 

Farther east in Hydra, as indicated near the left-hand 
edge of map No. 8, is a somewhat remarkable variable, 
R Hydra3. This star occasionally reaches magnitude 
three and a half, while at minimum it is not much above 
the tenth magnitude. Its period is about four hundred 
and twenty-five days. 

While we have been examining these comparatively 
barren regions, glad to find one or two colored doubles 
to relieve the monotony of the search, a glittering white 
star has frequently drawn our eyes eastward and upward. 
It is Spica, the great gem of Virgo, and, yielding to its 
attraction, we now enter the richer constellation over 
which it presides (map No. 9). Except for its beauty, 
which every one must admire, Spica, or a Virginis, has 
no special claim upon our attention. Some evidence has 
been obtained that, like /3 Auriga3 and Capella, it revolves 
with an invisible companion of great mass in an orbit only 
six million miles in diameter. Spica's spectrum resembles 
that of Sirius. The faint star which our larger apertures 
show about 6' northeast of Spica is of the tenth mag- 
nitude. 

Sweeping westward, we come upon 2 1669, a pretty 
little double with nearly equal components of about the 
sixth magnitude, distance 5.6", p. 124. But our interest 
is not fully aroused until we reach 7, a star with a history. 
The components of this celebrated binary are both nearly 



60 PLEASURES OF THE TELESCOPE 

of the third magnitude, distance about 5.8", p. 150. They 
revolve around their common center in something less 
than two hundred years. According to some authorities, 
the period is one hundred and seventy years, but it is not 
yet certainly ascertained. It was noticed about the be- 
ginning of the seventeenth century that 7 Virginis was 
double. In 1836 the stars were so close together that no 
telescope then in existence was able to separate them, 
although it is said that the disk into which they had 
merged was elongated at Pulkowa. In a few years they 
became easily separable once more. If the one-hundred- 
and-seventy-year period is correct, they should continue 
to get farther apart until about 1921. According to 
Asaph Hall, their greatest apparent distance is 6.3", and 
their least apparent distance 0.5"; consequently, they will 
never again close up beyond the separating power of ex- 
isting telescopes. 

There is a great charm in watching this pair of stars 
even with a three-inch telescope not so much on account 
of what is seen, although they are very beautiful, as on 
account of what we know they are doing. It is no slight 
thing to behold two distant stars obeying the law that 
makes a stone fall to the ground and compels the earth 
to swing round the sun. 

In 6 we discover a fine triple, magnitudes four and a 
half, nine, and ten; distances 7", p. 345, and 65", p. 295. 
The ninth-magnitude star has been described as " violet," 
but such designations of color are often misleading when 
the star is very faint. On the other hand it should not 
be assumed that a certain color does not exist because the 
observer can not perceive it, for experience shows that 
there is a wide difference among observers in the power 
of the eye to distinguish color. I have known persons 
who could not perceive the difference of hue in some of 



62 PLEASURES OF THE TELESCOPE 

the most beautifully contrasted colored doubles to be 
found in the sky. I am acquainted with an astronomer 
of long experience in the use of telescopes, whose eye is 
so deficient in color sense that he d'enies that there are 
any decided colors amongftje' stars. Such persons miss 
one of the finest pleasures of the telescope. In examining 
6 Virginis we shall do best to use our largest aperture, 
viz., the five-inch. Yet Webb records that all three of the 
stars in this triple have been seen with a telescope of only 
three inches aperture. The amateur must remember in 
such cases how T much depends upon practice as well as 
upon the condition of the atmosphere. There are lamen- 
tably few nights in a year when even the best telescope is 
ideally perfect in performance, but every night's obser- 
vation increases the capacity of the eye, begetting a kind 
of critical judgment which renders it to some extent inde- 
pendent of atmospheric vagaries. It will also be found 
that the idiosyncrasies of the observer are reflected in his 
instrument, w T hich seems to have its fits of excellence, its 
inspirations so to speak, while at other times it behaves 
as if all its wonderful powers had departed. 

Another double that perhaps we had better not try 
with less than four inches aperture is 84 Virginis. The 
magnitudes are six and nine; distance, 3.5", p. 233. Col- 
ors yellow and blue. 2 1846 is a fifth-magnitude star 
with a tenth-magnitude companion, distance only 4", 
p. 108. Use the five-inch. 

And now we approach something that is truly marvel- 
ous, the " Field of the Nebula?." This strange region, 
lying mostly in the constellation Virgo, is roughly out- 
lined by the stars /3, 77, 7, S, and e, which form two sides of 
a square some 15 across. It extends, however, for some 
distance into Coma Berenices, while outlying nebula? be- 
longing to it are also to be found in the eastern part of 



VIRGO AND HER NEIGHBORS 63 

Leo. Unfortunately for those who expect only brilliant 
revelations when they look through a telescope, this 
throng of nebula? consists of small and inconspicuous 
wisps as ill defined as bits of thistle-down floating high 
in the air. There are more than three hundred of them 
all told, but even the brightest are faint objects when 
seen with the largest of our telescopes. Why do they 
congregate thus? That is the question which lends an 
interest to the assemblage that no individual member of 
it could alone command. It is a mystery, but beyond 
question it is explicable. The explanation, however, is 
yet to be discovered. 

The places of only three of the nebula? are indicated on 
the map. No. 2806 has been described as resembling in 
shape a shuttle. Its length is nearly one third of the 
moon's diameter. It is brightest near the center, and has 
several faint companions. No. 2961 is round, in diame- 
ter, and is accompanied by another round nebula in the 
same field of view toward the south. No. 3105 is double, 
and powerful telescopes show two more ghostly compan- 
ions. There is an opportunity for good and useful work 
in a careful study of the little nebula? that swim into view 
all over this part of Virgo. Celestial photography has 
triumphs in store for itself here. 

Scattered over and around the region where the nebu- 
la? are thickest we find eight or nine variable stars, three 
of the most remarkable of which, K, S, and U, may be 
found on the map. R is very irregular, sometimes attain- 
ing magnitude six and a half, while at other times its 
maximum brightness does not exceed that of an eighth- 
magnitude star. At minimum it sinks to the tenth or 
eleventh magnitude. Its period is one hundred and forty- 
five days. U varies from magnitude seven or eight down 
to magnitude twelve or under and then regains its light, 



64: PLEASURES OF THE TELESCOPE 

in a period of about two hundred and seven days. S is 
interesting for its brilliant red color. When brightest, it 
exceeds the sixth magnitude, but at some of its maxima 
the magnitude is hardly greater 'than the eighth. At 
minimum it goes below the twelfth magnitude. Period, 
three hundred and seventy-six days. 

Next east of Virgo is Libra, which contains a few 
notable objects (map No. 10). The star a has a fifth-mag- 
nitude companion, distant about 230", which can be easily 
seen with an opera glass. At the point marked A on the 
map is a curious multiple star, sometimes referred to by 
its number in Piazzi's catalogues as follows: 212 P. xiv. 
The two principal stars are easily seen, their magnitudes 
being six and seven and a half; distance 15", p. 290. 
Burnham found four other faint companions, for which 
it would be useless for us to look. The remarkable thing 
is that these faint stars, the nearest of which is distant 
about 50" from the largest member of the group and the 
farthest about 129", do not share, according to their dis- 
coverer, in the rapid proper motion of the two main stars. 

In i we find a double a little difficult for our three-inch. 
The components are of magnitudes four and a half and 
nine, distance 57", p. 110. Burnham discovered that 
the ninth-magnitude star consists of two of the tenth less 
than 2" apart, p. 24. 

No astronomer who happens to be engaged in this part 
of the sky ever fails, unless his attention is absorbed by 
something of special interest, to glance at /? Libra?, which 
is famous as the only naked-eye star having a decided 
green color. The hue is pale, but manifest.* 

The star is a remarkable variable, belonging to what 
is called the Algol type. Its period, according to Chan- 

* Is the slight green tint perceptible in Sirius variable ? I am sometimes dis- 
posed to think it is. 



66 PLEASURES OF THE TELESCOPE 

dler, is 2 days 7 hours, 51 minutes, 22.8 seconds. The time 
occupied by the actual changes is about twelve hours. At 
maximum the star is of magnitude five and at minimum of 
magnitude 6.2. 

We may now conveniently turn northward from Virgo 
in order to explore Bootes, one of the most interesting of 
the constellations (map No. 11). Its leading star a, Arctu- 
rus, is the brightest in the northern hemisphere. Its pre- 
cedence over its rivals Vega and Capella, long in dispute, 
has been settled by the Harvard photometry. You notice 
that the color of Arcturus, when it has not risen far above 
the horizon, is a yellowish red, but when the star is near 
mid-heaven the color fades to light yellow. The hue is 
possibly variable, for it is recorded that in 1852 Arctu- 
rus appeared to have nearly lost its color. If it should 
eventually turn white, the fact would have an important 
bearing upon the question whether Sirius was, as alleged, 
once a red or flame-colored star. 

But let us sit here in the starlight, for the night is 
balmy, and talk about Arcturus, which is perhaps actually 
the greatest sun within the range of terrestrial vision. 
Its parallax is so minute that the consideration of the 
tremendous size of this star is a thing that the imagina- 
tion can not placidly approach. Calculations, based on 
its assumed distance, which show that it outshines the sun 
several thousand times, may be no exaggeration of the truth! 
It is easy to make such a calculation. One of Dr. Elkin's 
parallaxes for Arcturus is 0.018". That is to say, the dis- 
placement of Arcturus due to the change in the observer's 
point of view when he looks at the star first from one 
side and then from the other side of the earth's orbit, 
186,000,000 miles across, amounts to only eighteen one- 
thousandths of a second of arc. We can appreciate how 
small that is when we reflect that it is about equal to the 



,A MAJOR 



RONA BOREALIS 



SERPENS 



:ANES VENATICI 



MAP No. 11. 



68 PLEASURES OF THE TELESCOPE 

apparent distance between the heads of two pins placed 
an inch apart and viewed from a distance of a hundred 
and eighty miles! 

Assuming this estimate of the parallax of Arcturus, 
let us see how it will enable us to calculate the probable 
size or light-giving power of the star as compared with the 
sun. The first thing to do is to multiply the earth's dis- 
tance from the sun, which may be taken at 93,000,000 
miles, by 206,265, the number of seconds of arc in a radian, 
the base of circular measure, and then divide the product 
by the parallax of the star. Performing the multiplica- 
tion and division, we get the following: 

19,182,645,000,000 _ 1)065>790>250)000>000 . 

The quotient represents miles! Call it, in round numbers, 
a thousand millions of millions of miles. This is about 
11,400,000 times the distance from the earth to the sun. 

Now for the second part of the calculation: The 
amount of light received on the earth from some of the 
brighter stars has been experimentally compared w r ith the 
amount received from the sun. The results differ rather 
widely, but in the case of Arcturus the ratio of the star's 
light to sunlight may be taken as about one twenty-five- 
thousand-millionth i. e., 25,000,000,000 stars, each equal 
to Arcturus, would together shed upon the earth as much 
light as the sun does. But we know that light varies in- 
versely as the square of the distance; for instance, if the 
sun were twice as far away as it is, its light would be 
diminished for us to a quarter of its present amount. 
Suppose, then, that we could remove the earth to a point 
midway between the sun and Arcturus, we should then 
be 5,700,000 times as far from the sun as we now are. In 
order to estimate how much light the sun would send us 
from that distance we must square the number 5,700,000 



VIRGO AND HER NEIGHBORS 69 

and then take the result inversely, or as a fraction. We 

thUS get 32,490,000,000,000, re P reseptin g the ratio of the 
sun's light at half the distance of Arcturus to that at its 
real distance. But while receding from the sun we should 
be approaching Arcturus. We should get, in fact, twice 
as near to that star as we were before, and therefore its 
light would be increased for us fourfold. Now, if the 
amount of sunlight had not changed, it would exceed the 
light of Arcturus only a quarter as much as it did before, 

or in the ratio of 25 ' 000 '0 ' 000 = 6,250,000,000 to 1. But, 

as we have seen, the sunlight would diminish through in- 
crease of distance to one 32,490,000,000,000th part of its 
original amount. Hence its altered ratio to the light of 
Arcturus would become 6,250,000,000 to 32,490,000,000,000, 
or 1 to 5,198. 

This means that if the earth were situated midway 
between the sun and Arcturus, it would receive 5,198 
times as much, light from that star as it would from the 
sun! It is quite probable, moreover, that the heat of 
Arcturus exceeds the solar heat in the same ratio, for 
the spectroscope shows that although Arcturus is sur- 
rounded with a cloak of metallic vapors proportionately 
far more extensive than the sun's, yet, smothered as the 
great star seems in some respects to be, it rivals Sirius 
itself in the intensity of its radiant energy. 

If we suppose the radiation of Arcturus to be the same 
per unit of surface as the sun's, it follows that Arcturus 
exceeds the sun about 375,000 times in volume, and that 
its diameter is no less than 62,350,000 miles! Imagine the 
earth and the other planets constituting the solar system 
removed to Arcturus and set revolving around it in orbits 
of the same forms and sizes as those in which they circle 



70 PLEASURES OF THE TELESCOPE 

about the sun. Poor Mercury! For that little planet it 
would indeed be a jump from the frying pan into the fire, 
because, as it rushed to perihelion, Mercury would plunge 
more than 2,500,000 miles beneath the surface of the giant 
star. Venus and the earth would melt like snowflakes 
at the mouth of a furnace. Even far-away Neptune, the 
remotest member of the system, would swelter in torrid 
heat. 

But stop! Look at the sky. Observe how small and 
motionless the disks of the stars have become. Back to 
the telescopes at once, for this is a token that the atmos- 
phere is steady, and that " good seeing " may be ex- 
pected. It is fortunate, for we have some delicate work 
before us. The very first double star we try in Bootes, X 
1772, requires the use of the four-inch, and the five-inch 
shows it more satisfactorily. The magnitudes are sixth 
and ninth, distance 5", p. 140. On the other side of Arc- 
turus we find f, a star that we should have had no great 
difficulty in separating thirty years ago, but which has 
now closed up beyond the reach even of our five-inch. 
The magnitudes are both fourth, and the distance less than 
a quarter of a second; position angle changing. It is ap- 
parently a binary, and if so will some time widen again, 
but its period is unknown. The star 279, also known as 5 
1910, near the southeastern edge of the constellation, is a 
pretty double, each component being of the seventh mag- 
nitude, distance 4", p. 212. Just above f we come upon 
TT, an easy double for the three-inch, magnitudes four and 
six, distance 6" p. 99. Next is f, a yellow and purple 
pair, whose magnitudes are respectively five and seven, 
distance less than 3", p. 200. This is undoubtedly a bi- 
nary with a period of revolution of about a hundred and 
thirty years. Its distance decreased about V between 
1881 and 1891. It was still decreasing in 1899, when it 



VIRGO AND HER NEIGHBORS 71 

had become 2.5". The orbital swing is also very apparent 
in the change of the position angle. 

The telescopic gem of Bootes, and one of " the flowers 
of the sky," is e, also known as Mirac. When well seen, 
as we shall see it to-night, e Bootis is superb. The mag- 
nitudes of its two component stars are two and a half (ac- 
cording to Hall, three) and six. The distance is about 
2.8", p. 326. The contrast of colors bright orange 
yellow, set against brilliant emerald green is mag- 
nificent. There are very few doubles that can be com- 
pared with it in this respect. The three-inch will sepa- 
rate it, but the five-inch enables us best to enjoy its 
beauty. It appears to be a binary, but the motion is very 
slow, and nothing certain is yet known of its period. 

In 8 we have a very wide and easy double; magnitudes 
three and a half and eight and a half, distance 110", p. 
75. The smaller star has a lilac hue. We can not hope 
with any of our instruments to see all of the three stars 
contained in /*, but two of them are easily seen; magni- 
tudes four and seven, distance 108", p. 172. The smaller 
star is again double; magnitudes seven and eight, dis- 
tance 0.77", p. 88. It is clearly a binary, with a long 
period. A six-inch telescope that could separate this star 
at present would be indeed a treasure. % 1926 is another 
object rather beyond our powers, on account of the con- 
trast of magnitudes. These are six and eight and a half; 
distance 1.3", p. 256. 

Other doubles are: 44 (21909), magnitudes five and 
six, distance 4.8", p. 240; 39 (1890), magnitudes both 
nearly six, distance 3.6", p. 45. Smaller star light red; t, 
magnitudes four and a half and seven and a half, distance 
38", p. 33; *, magnitudes five and a half and eight, dis- 
tance 12.7", p. 238. Some observers see a greenish tinge 
in the light of the larger star, the smaller one being blue. 



72 PLEASURES OF THE TELESCOPE 

There are one or two interesting things to be seen in 
that part of Canes Venatici which is represented on map 
No. 11. The first of these is the star cluster 3936. This 
will reward a good look with the five-inch. With large 
telescopes as many as one thousand stars have been dis- 
cerned packed within its globular outlines. 

The star 25 (2 1768) is a close binary with a period 
estimated at one hundred and twenty-five years. The 
magnitudes are six and seven or eight, distance about 1", 
p. 137. We may try for this with the five-inch, and if we 
do not succeed in separating the stars we may hope to do 
so some time, for the distance between them is increasing. 

Although the nebula 3572 is a very wonderful object, 
we shall leave it for another evening. 

Eastward from Bootes shines the circlet of Corona 
Borealis, whose form is so strikingly marked out by the 
stars that the most careless eye perceives it at once. 
Although a very small constellation, it abounds with in- 
teresting objects. We begin our attack with the five-inch 
on S 1932, but not too confident that we shall come off 
victors, for this binary has been slowly closing for many 
years. The magnitudes are six and a half and seven, dis- 
tance 0.84", p. 150. Not far distant is another binary, at 
present beyond our powers, rj. Here the magnitudes are 
both six, distance 0.65", p. 3. Hall assigns a period of 
forty years to this star. 

The assemblage of close binaries in this neighborhood 
is very curious. Only a few degrees away we find one 
that is still more remarkable, the star 7. What has previ- 
ously been said about 42 Coma? Berenicis applies in a 
measure to this star also. It, too, has a comparatively 
small orbit, and its components are never seen widely 
separated. In 1826 their distance was 0.7"; in 1880 they 
could not be split; in 1891 the distance had increased to 



VIRGO AND HER NEIGHBORS 73 

0.36", and in 1894 it had become 0.53", p. 123. But in 
1899 Lewis made the distance only 0.43". The period has 
been estimated at one hundred years. 

While the group of double stars in the southern part 
of Corona Borealis consists, as we have seen, of remark- 
ably close binaries, another group in the northern part of 
the same constellation comprises stars that are easily 
separated. Let us first try ?. The powers of the three- 
inch are amply sufficient in this case. The magnitudes 
are four and five, distance 6.3", p. 300. Colors, white or 
bluish-white and blue or green. 

Next take cr ? whose magnitudes are five and six, dis- 
tance 4", p. 206. With the five-inch we may look for a 
second companion of the tenth magnitude, distance 54", 
p. 88. It is thought highly probable that <r is a binary, 
but its period has simply been guessed at. 

Finally, we come to z/, which consists of two very 
widely separated stars, v 1 and i> 2 , each of which has a faint 
companion. With the five-inch we may be able to see the 
companion of z> 2 , the more southerly of the pair. The 
magnitude of the companion is variously given as tenth 
and twelfth, distance 137", p. 18. 

With the aid of the map we find the position of the 
new star of 1866, which is famous as the first so-called 
temporary star to which spectroscopic analysis was ap- 
plied. When first noticed, on May 12, 1866, this star was 
of the second magnitude, fully equaling in brilliancy a, 
the brightest star of the constellation; but in about two 
weeks it fell to the ninth magnitude. Huggins and Mil- 
ler eagerly studied the star with the spectroscope, and 
their results were received with deepest interest. They 
concluded that the light of the new star had two different 
sources, each giving a spectrum peculiar to itself. One of 
the spectra had dark lines and the other bright lines. It 
6 



74 PLEASURES OF THE TELESCOPE 

will be remembered that a similar peculiarity was exhib- 
ited by the new star in Auriga in 1893. But the star in 
Corona did not disappear. It diminished to magnitude 
nine and a half or ten, and stopped 'there; and it is still 
visible. In fact, subsequent examination proved that it 
had been catalogued at Bonn as a star of magnitude nine 
and a half in 1855. Consequently this " blaze star " of 
1866 will bear watching in its decrepitude. Nobody 
knows but that it may blaze again. Perhaps it is a sun- 
like body; perhaps it bears little resemblance to a sun 
as we understand such a thing. But whatever it may be, 
it has proved itself capable of doing very extraordinary 
things. 

We have no reason to suspect the sun of any latent 
eccentricities, like those that have been displayed by 
"temporary" stars; yet, acting on the principle which 
led the old emperor-astrologer Rudolph II to torment his 
mind with self-made horoscopes of evil import, let us un- 
scientifically imagine that the sun could suddenly burst 
out with several hundred times its ordinary amount of 
heat and light, thereby putting us into a proper condition 
for spectroscopic examination by curious astronomers in 
distant worlds. 

But no, after all, it is far pleasanter to keep within 
the strict boundaries of science, and not imagine anything 
of the kind. 



CHAPTER V 

IN SUMMER STAR-LANDS. 

" I heard the trailing garments of the night 

Sweep through her marble halls, 
I saw her sable skirts all fringed with light 

From the celestial walls. " H. W. LONGFELLOW. 

IN the soft air of a summer night, when fireflies are 
flashing their lanterns over the fields, the stars do not 
sparkle and blaze like those that pierce the frosty skies of 
winter. The light of Sirius, Aldebaran, Rigel, and other 
midwinter brilliants possesses a certain gemlike hardness 
and cutting quality, but Antares and Vega, the great 
summer stars, and Arcturus, when he hangs westering in 
a July night, exhibit a milder radiance, harmonizing with 
the character of the season. This difference is, of course, 
atmospheric in origin, although it may be partly subjec- 
tive, depending upon the mental influences of the muta- 
tions of Nature. 

The constellation Scorpio is nearly as striking in out- 
line as Orion, and its brightest star, the red Antares (a in 
map No. 12), carries concealed in its rays a green jewel 
which, to the eye of the enthusiast in telescopic recrea- 
tion, appears more beautiful and inviting each time that 
he penetrates to its hiding place. 

We shall begin our night's work with this object, and 
the four-inch glass will serve our purpose, although the 
untrained observer would be more certain of success with 

75 



76 PLEASURES OF THE TELESCOPE 

the five-inch. A friend of mine has seen the companion 
of Antares with a three-inch, but I have never tried the 
star with so small an aperture. When the air is steady 
and the companion can be well viewed, there is no finer 
sight among the double stars. The contrast of colors is 
beautifully distinct fire-red and bright green. The little 
green star has been seen emerging from behind the moon, 
ahead of its ruddy companion. The magnitudes are one 
and seven and a half or eight, distance 3", p. 270. An- 
tares is probably a binary, although its binary character 
has not yet been established. 

A slight turn of the telescope tube brings us to the 
star (7, a wide double, the smaller component of which is 
blue or plum-colored; magnitudes four and nine, distance 
20", p. 272. From <r we pass to /?, a very beautiful object, 
of which the three-inch gives us a splendid view. Its two 
components are of magnitudes two and six, distance 13", 
p. 30; colors, white and bluish. It is interesting to know 
that the larger star is itself double, although none of the 
telescopes we are using can split it. Burnham discovered 
that it has a tenth-magnitude companion; distance less 
than 1", p. 87. 

And now for a triple, which will probably require the 
use of our largest glass. Up near the end of the northern 
prolongation of the constellation we perceive the star f. 
The three-inch shows us that it is double; the five-inch 
divides the larger star again. The magnitudes are respec- 
tively five, five and a half, and seven and a half, distances 
0.94", p. 215, and 7", p. 70. 

A still more remarkable star, although one of its com- 
ponents is beyond our reach, is v. With the slightest 
magnifying this object splits up into two stars, of magni- 
tudes four and seven, situated rather more than 40" apart. 
A high power divides the seventh-magnitude companion 



78 PLEASURES OF THE TELESCOPE 

into two, each of magnitude six and a half, distance 1.8", 
p. 42. But (and this was another of Burnham's discover- 
ies) the fourth-magnitude star itself is double, distance 
0.8", p. about 0. The companion in this case is of mag- 
nitude five and a half. 

Next we shall need a rather low-power eyepiece and 
our largest aperture in order to examine a star cluster, 
No. 4173, which was especially admired by Sir William 
Herschel, who discovered that it was not, as Messier had 
supposed, a circular nebula. Herschel regarded it as the 
richest mass of stars in the firmament, but with a small 
telescope it appears merely as a filmy speck that has 
sometimes been mistaken for a comet. In 1860 a new 
star, between the sixth and seventh magnitude in bril- 
liance, suddenly appeared directly in or upon the cluster, 
and the feeble radiance of the latter was almost extin- 
guished by the superior light of the stranger. The latter 
disappeared in less than a month, and has not been seen 
again, although it is suspected to be a variable, and, as 
such, has been designated with the letter T. Two other 
known variables, both very faint, exist in the immediate 
neighborhood. According to the opinion that was for- 
merly looked upon with favor, the variable T, if it is 
a variable, simply lies in the line of sight between the 
earth and the star cluster, and has no actual connection 
with the latter. But this opinion may not, after all, be 
correct, for Mr. Bailey's observations show that variable 
stars sometimes exist in large numbers in clusters, al- 
though the variables thus observed are of short period. 
The cluster 4183, just west of Antares, is also worth a 
glance with the five-inch glass. It is dense, but its stars 
are very small, so that to enjoy its beauty we should have 
to employ a large telescope. Yet there is a certain attrac- 
tion in these far-away glimpses of starry swarms, for they 



IN SUMMER STAR-LANDS 79 

give us some perception of the awful profundity of space. 
When the mind is rightly attuned for these revelations 
of the telescope, there are no words that can express its 
impressions of the overwhelming perspective of the uni- 
verse. 

The southern part of the constellation Ophiuchus is 
almost inextricably mingled with Scorpio. We shall, 
therefore, look next at its attractions, beginning with the 
remarkable array of star clusters 4264, 4268, 4269, and 
4270. All of these are small, 2' or 3' in diameter, and 
globular in shape. No. 4264 is the largest, and we can 
see some of the stars composing it. But these clusters, 
like those just described in Scorpio, are more interesting 
for what they signify than for what they show; and the 
interest is not diminished by the fact that their meaning 
is more or less of a mystery. Whether they are composed 
of pygmy suns or of great solar globes like that one which 
makes daylight for the earth, their association in spher- 
ical groups is equally suggestive. 

'There are two other star clusters in Ophiuchus, and 
within the limits of map No. 12, both of which are more 
extensive than those we have just been looking at. No. 
4211 is 5' or 6' in diameter, also globular, brighter at the 
center, and surrounded by several comparatively con- 
spicuous stars. No. 4346 is still larger, about half as 
broad as the moon, and many of its scattered stars are of 
not less than the ninth magnitude. With a low mag- 
nifying power the field of view surrounding the cluster 
appears powdered with stars. 

There are only two noteworthy doubles in that part of 
Ophiuchus with which we are at present concerned: 36, 
whose magnitudes are five and seven, distance 4.3", p. 
195, colors yellow and red; and 39, magnitudes six and 
seven and a half, distance 12", p. 356, colors yellow or 



80 PLEASURES OF THE TELESCOPE 

orange and blue. The first named is a binary whose 
period has not been definitely ascertained. 

The variable R has a period a little less than three hun- 
dred and three days. At its brightest it is of magnitude 
seven or eight, and at minimum it diminishes to about the 
twelfth magnitude. 

The spot where the new star of 1604 appeared is indi- 
c^ated on the map. This was, with the exception of 
Tycho's star in 1572, the brightest temporary star of 
which we possess a trustworthy account. It is frequently 
referred to as Kepler's star, because Kepler watched it 
with considerable attention, but unfortunately he was not 
as good an observer as Tycho was. The star was first 
seen on October 10, 1604, and was then brighter than 
Jupiter. It did not, however, equal Venus. It gradually 
faded and in March, 1606, disappeared. About twelve de- 
grees northwest of the place of the star of 1604, and in 
that part of the constellation Serpens which is included 
in map No. 12, we find the location of another temporary 
star, that of 1848. It was first noticed by Mr. Hind on 
April 28th of that year, when its magnitude was not much 
above the seventh, and its color was red. It brightened 
rapidly, until on May 2d it was of magnitude three and a 
half. Then it began to fade, but very slowly, and it has 
never entirely disappeared. It is now of the twelfth or 
thirteenth magnitude. 

In passing we may glance with a low power at v Ser- 
pentis, a wide double, magnitudes four and nine, distance 
50", p. 31, colors contrasted but uncertain. 

Sagittarius and its neighbor, the small but rich constel- 
lation Scutum Sobieskii, attract us next. We shall first 
deal with the western portions of these constellations 
which are represented on Map No. 12. The star /* in Sa- 
gittarius is a wide triple, magnitudes three and a half, 



IN SUMMER STAR-LANDS 81 

nine and a half, and ten, distances 40", p. 315, and 45", p. 
114. But the chief glory of Sagittarius (and the same 
statement applies to Scutum Sobieskii) lies in its assem- 
blage of star clusters. One of these, No. 4361, also known 
as M 8, is plainly visible to the naked eye as a bright spot 
in the Milky Way. We turn our five-inch telescope, armed 
with a low magnifying power, upon this subject and enjoy 
a rare spectacle. As we allow it to drift through the field 
we see a group of three comparatively brilliant stars 
advancing at the front of a wonderful train of mingled 
star clusters and nebulous clouds. A little northwest of 
it appea'rs the celebrated trifid nebula, No. 4355 on the 
map. There is some evidence that changes have occurred 
in this nebula since its discovery in the last century. Bar- 
nard has made a beautiful photograph showing M 8 and 
the trifid nebula on the same plate, and he remarks that 
the former is a far more remarkable object than, its more 
famous neighbor. Near the eastern border of the princi- 
pal nebulous cloud there is a small and very black hole 
with a star poised on its eastern edge. This hole and the 
star are clearly shown in the photograph. 

Cluster No. 4397 (M 24) is usually described as resem- 
bling, to the naked eye, a protuberance on the edge of the 
Milky Way. It is nearly three times as broad as the 
moon, and is very rich in minute stars, which are at just 
such a degree of visibility that crowds of them continually 
appear and disappear while the eye wanders over the field, 
just as faces are seen and lost in a vast assemblage of 
people. This kind of luminous agitation is not peculiar 
to M 24, although that cluster exhibits it better than most 
others do on account of both the multitude and the mi- 
nuteness of its stars. 

A slight sweep eastward brings us to yet another meet- 
ing place of stars, the cluster M 25, situated between the 



82 PLEASURES OF THE TELESCOPE 

variables U and V. This is brilliant and easily resolved 
into its components, which include a number of double 
stars. 

The two neighboring variables just referred to are 
interesting. U has a period of about six days and three 
quarters, and its range of magnitude runs from the 
seventh down to below the eighth. V is a somewhat mys- 
terious star. Chandler removed it from his catalogue of 
variables because no change had been observed in its light 
by either himself, Sawyer, or Yendell. Quirling, the dis- 
coverer of its variability, gave the range as between mag- 
nitudes 7.6 and 8.8. It must, therefore, be exceedingly 
erratic in its changes, resembling rather the temporary 
stars than the true variables. 

In that part of Scutum Sobieskii contained in map 
No. 12 we find an interesting double, 2 2325, whose magni- 
tudes are six and nine, distance 12.3", p. 260, colors white 
and orange. S 2306 is a triple, magnitudes seven, eight, 
and nine, distances 12", p. 220, and 0.8", p. 68. The 
third star is, however, beyond our reach. The colors of 
the two larger are respectively yellow and violet. 

The star cluster 4400 is about one quarter as broad 
as the moon, and easily seen with our smallest aperture. 

Passing near to the region covered by map No. 13, we 
find the remaining portions of the constellations Sagitta- 
rius and Scutum Sobieskii. It will be advisable to finish 
with the latter first. Glance at the clusters 4426 and 
4437. Neither is large, but both are rich in stars. The 
nebula 4441 is a fine object of its kind. It brightens to- 
ward the center, and Herschel thought he had resolved it 
into stars. The variable R is remarkable for its eccen- 
tricities. Sometimes it attains nearly the fourth magni- 
tude, although usually at maximum it is below the fifth, 
while at minimum it is occasionally of the sixth and at 



84 PLEASURES OF THE TELESCOPE 

other times of the seventh or eighth magnitude. Its 
period is irregular. 

Turning back to Sagittarius, we resume our search for 
interesting objects there, and the frst that we discover is 
another star cluster, for the stars are wonderfully grega- 
rious in this quarter of the heavens. The number our 
cluster bears on the map is 4424, corresponding with M 22 
in Messier's catalogue. It is very bright, containing 
many stars of the tenth and eleventh magnitudes, as well 
as a swarm of smaller ones. Sir John Herschel regarded 
the larger stars in this cluster as possessing a reddish 
tint. Possibly there was some peculiarity in his eye that 
gave him this impression, for he has described a cluster 
in the constellation Toucan in the southern hemisphere as 
containing a globular mass of rose-colored stars inclosed 
in a spherical shell of white stars. Later observers have 
confirmed his description of the shape and richness of this 
cluster in Toucan, but have been unable to perceive the 
red hue of the interior stars. 

The eastern expanse of Sagittarius is a poor region 
compared with the western end of the constellation, 
where the wide stream of the Milky Way like a great river 
enriches its surroundings. The variables T and R are of 
little interest to us, for they never become bright enough 
to be seen without the aid of a telescope. In 54 we find, 
however, an interesting double, which with larger tele- 
scopes than any of ours appears as a triple. The two 
stars that we see are of magnitudes six and seven and a 
half, distance 45", p. 42, colors yellow and blue. The 
third star, perhaps of thirteenth magnitude, is distant 
36", p. 245. 

Retaining map No. 13 as our guide, we examine the 
western part of the constellation Capricornus. Its leader 
a is a naked-eye double, the two stars being a little more 



IN SUMMER STAR-LANDS 85 

than 6' apart. Their magnitudes are three and four, and 
both have a yellowish hue. The western star is a 1 , and is 
the fainter of the two. The other is designated as a\ 
Both are double. The components of a 1 are of magni- 
tudes four and eight and a half, distance 44", p. 220. 
With the Washington twenty-six-inch telescope a third 
star of magnitude fourteen has been found at a distance 
of 40", p. 182. In a 2 the magnitudes of the components 
are three and ten and a half, distance 7.4", p. 150. The 
smaller star has a companion of the twelfth or thirteenth 
magnitude, distance 1.2", p. 240. This, of course, is 
hopelessly beyond our reach. Yet another star of magni- 
tude nine, distance 154", p. 156 , we may see easily. 

Dropping down to j3, we find it to be a most beautiful 
and easy double, possessing finely contrasted colors, gold 
and blue. The larger star is of magnitude three, and the 
smaller, the blue one, of magnitude six, distance 205", 
p. 267. Between them there is a very faint star which 
larger telescopes than ours divide into two, each of mag- 
nitude eleven and a half; separated 3", p. 325. 

Still farther south and nearly in a line drawn from a 
through we find a remarkable group of double stars, o-, 
TT, p, and o. The last three form a beautiful little tri- 
angle. We begin with cr, the faintest of the four. The 
magnitudes of its components are six and nine, distance 
54", p. 177. In TT the magnitudes are five and nine, dis- 
tance 3.4", p. 145; in /o, magnitudes five and eight, dis- 
tance 3.8", p. 177 (a third star of magnitude seven and a 
half is seen at a distance of 4', p. 150); in o, magnitudes 
six and seven, distance 22", p. 240. 

The star cluster 4608 is small, yet, on a moonless night, 
worth a glance with the five-inch. 

We now pass northward to the region covered by map 
No. 14, including the remainder of Ophiuchus and Serpens. 



86 PLEASURES OF THE TELESCOPE 

Beginning with the head of Serpens, in the upper right- 
hand corner of the map, we find that /:?, of magnitude 
three and a half, has a ninth-magnitude companion, dis- 
tance 30", p. 265. The larger star is light blue and the 
smaller one yellowish. The little star v is double, mag- 
nitudes five and nine, distance 50", p. 31, colors con- 
trasted but uncertain. In S we find a closer double, mag- 
nitudes three and four, distance 3.5", p. 190. It is a 
beautiful object for the three-inch. The leader of the con- 
stellation, a, of magnitude tw r o and a half, has a faint com- 
panion of only the twelfth magnitude, distance 60", p. 
350. The small star is bluish. The variable R has a 
period about a week short of one year, and at maximum 
exceeds the sixth magnitude, although sinking at mini- 
mum to less than the eleventh. Its color is ruddy. 

Passing eastward, we turn again into Ophiuchus, and 
find immediately the very interesting double, X, whose 
components are of magnitudes four and six, distance 1", 
p. 55. This is a long-period binary, and notwithstanding 
the closeness of its stars, our four-inch should separate 
them when the seeing is fine. We shall do better, how- 
ever, to try. with the five-inch. 2 2166 consists of two 
stars of magnitudes six and seven and a half, distance 27", 
p. 280. 2 2173 is a double of quite a different order. 
The magnitudes of its components are both six, the dis- 
tance in 1899 0.98", p. 331. It is evidently a binary in 
rapid motion, as the distance changed from about a quar- 
ter of a second in 1881 to more than a second in 1894. The 
star T is a fine triple, magnitudes five, six, and nine, dis- 
tances 1.8", p. 254, and 100", p. 127. The close pair is a 
binary system with a long period of revolution, estimated 
at about two hundred years. We discover another group 
of remarkable doubles in 67, 70, and 73. In the first- 
named star the magnitudes are four and eight, distance 



88 PLEASURES OF THE TELESCOPE 

55", p. 144, colors finely contrasted, pale yellow and 
red. 

Much more interesting, however, is 70, a binary whose 
components have completed a revolution since their 
discovery by Sir William Herschel, the period being 
ninety-five years. The magnitudes are four and six, or, 
according to Hall, five and six, distance in 1894 2.3"; in 
1900, 1.45", according to Maw. Hall says the apparent 
distance when the stars are closest is about 1.7", and when 
they are widest 6.7". This star is one of those whose par- 
allax has been calculated with a reasonable degree of ac- 
curacy. Its distance from us is about 1,260,000 times the 
distance of the sun, the average distance apart of the two 
stars is about 2,800,000,000 miles (equal to the distance of 
Neptune from the sun), and their combined mass is three 
times that of the sun. Hall has seen in the system of 
70 Ophiuchi three stars of the thirteenth magnitude or 
less, at distances of about 60", 90", and 165" respectively. 

The star 73 is also a close double, and beyond our 
reach. Its magnitudes are six and seven, distance 0.7", 
p. 245. It is, no doubt, a binary. 

Three star clusters in Ophiuchus remain to be exam- 
ined. The first of these, No. 4256, is partially resolved 
into stars by the five-inch. No. 4315 is globular, and has 
a striking environment of bystanding stars. It is about 
one quarter as broad as the full moon, and our largest 
aperture reveals the faint coruscation of its crowded com- 
ponents. No. 4410 is a coarser and more scattered star 
swarm a fine sight! 

Farther toward the east we encounter a part of Ser- 
pens again, which contains just one object worth glancing 
at, the double 0, whose stars are of magnitudes four and 
four and a half, distance 21", p. 104. Color, both yellow, 
the smaller star having the deeper hue. 



IN SUMMER STAR-LANDS 89 

Let us next, with the guidance of map No. 15, enter the 
rich star fields of Hercules, and of the head and first coils 
of Draco. According to Argelander, Hercules contains 
more stars visible to the naked eye than any other con- 
stellation, and he makes the number of them one hundred 
and fifty-five, nearly two thirds of which are only of the 
sixth magnitude. But Heis, who saw more naked-eye 
stars than Argelander, makes Ursa Major precisely equal 
to Hercules in the number of stars, his enumeration show- 
ing two hundred and twenty-seven in each constellation, 
while, according to him, Draco follows very closely after, 
with two hundred and twenty stars. Yet, on account of 
the minuteness of the majority of their stars, neither of 
these constellations makes by any means as brilliant a 
display as does Orion, to which Argelander assigns only 
one hundred and fifteen naked-eye stars, and Heis one 
hundred and thirty-six. 

We begin in Hercules with the star K, a pretty little 
double of magnitudes five and a half and seven, distance 
31", p. 10, colors yellow and red. Not far away we find, 
in 7, a larger star with a fainter companion, the magni- 
tudes in this case being three and a half and nine, dis- 
tance 38", p, 242, colors white and faint blue or lilac. 
One of the most beautiful of double stars is a Herculis. 
The magnitudes are three and six, distance 4.7", p. 118, 
colors orange and green, very distinct. Variability has 
been ascribed to each of the stars in turn. It is not 
known that they constitute a binary system, because no 
certain evidence of motion has been obtained. Another 
very beautiful and easily separated double is , magni- 
tudes three and eight, distance 19", p. 175, colors pale 
green and purple. 

Sweeping northwestward to f, we encounter a cele- 
brated binary, to separate which at present requires the 

7 



90 PLEASURES OF THE TELESCOPE 

higher powers of a six-inch glass. The magnitudes are 
three and six and a half, distance in 1899, 0.6", p. 264; in 
1900, 0.8", p. 239. The period of revolution is thirty-five 
years, and two complete revolutions have been observed. 
The apparent distance changes from 0.6" to 1.6". They 
were at their extreme distance in 1884. 

Two pleasing little doubles are 2 2101, magnitudes six 
and nine, distance 4", p. 57, and 2 2104, magnitudes six 
and eight, distance 6", p. 20. At the northern end of the 
constellation is 42, a double that requires the light-grasp- 
ing power of our largest glass. Its magnitudes are six 
and twelve, distance 20", p. 94. In p we discover another 
distinctly colored double, both stars being greenish or 
bluish, with a difference of tone. The magnitudes are 
four and five and a half, distance 3.7", p. 309. But the 
double 95 is yet more remarkable for the colors of its 
stars. Their magnitudes are five and five and a half, dis- 
tance 6", p. 262, colors, according to Webb, " light apple- 
green and cherry-red." But other observers have noted 
different hues, one calling them both golden yellow. I 
think Webb's description is more nearly correct. 2 2215 
is a very close double, requiring larger telescopes than 
those we are working with. Its magnitudes are six and a 
half and eight, distance 0.7", p. 300. It is probably a 
binary. 2 2289 is also close, but our five-inch will 
separate it: magnitudes six and seven, distance 1.2", 
p. 230. 

Turning to ^, we have to deal with a triple, one of 
whose stars is at present beyond the reach of our instru- 
ments. The magnitudes of the two that we see are four 
and ten, distance 31", p. 243. The tenth-magnitude star 
is a binary of short period (probably less than fifty years), 
the distance of whose components was 2" in 1859, 1" in 
1880, 0.34" in 1889, and 0.54" in 1891, when the position 



URSA MIN 



CORONA BOR. 



HERCULES 



OPHIUCHUS 



MAP No 15 



SERPENS 



92 PLEASURES OF THE TELESCOPE 

angle was 25, and rapidly increasing. The distance is 
still much less than 1". 

For a glance at a planetary nebula we may turn with 
the five-inch to No. 4234. It is very small and faint, only 
8" in diameter, and equal in brightness to an eighth- 
magnitude star. Only close gazing shows that it is not 
sharply defined like a star, and that it possesses a bluish 
tint. Its spectrum is gaseous. 

The chief attraction of Hercules we have left for the 
last, the famous star cluster between rj and , No. 4230, 
more commonly known as M 13. On a still evening in the 
early summer, when the moon is absent and the quiet that 
the earth enjoys seems an influence descending from the 
brooding stars, the spectacle of this sun cluster in Hercu- 
les, viewed with a telescope of not less than five-inches 
aperture, captivates the mind of the most uncontempla- 
tive observer. With the Lick telescope I have watched it 
resolve into separate stars to its very center a scene of 
marvelous beauty and impressiveness. But smaller in- 
struments reveal only the in-running star streams and the 
sprinkling of stellar points over the main aggregation, 
whirh cause it to sparkle like a cloud of diamond dust 
transfused with sunbeams. The appearance of flocking 
together that those uncountable thousands of stars pre- 
sent calls up at once a picture of our lone sun separated 
from its nearest stellar neighbor by a distance probably a 
hundred times as great as the entire diameter of the 
spherical space within which that, multitude is congre- 
gated. It is true that unless we assume what would seem 
an unreasonable remoteness for the Hercules cluster, its 
component stars must be much smaller bodies than the 
sun; yet even that fact does not diminish the wonder of 
their swarming. Here the imagination must bear science 
on its wings, else science can make no progress whatever. 



IX SUMMED STAR-LANDS 93 

It is an easy step Jrom Hercules to Draco. In the con- 
spicuous diamond-shaped figure that serves as a guide- 
board to the head of the latter, the southernmost star be- 
longs not to Draco but to Hercules. The brightest star 
in this figure is 7, of magnitude two and a half, with 
an eleventh-magnitude companion, distant 125", p. 116. 
Two stars of magnitude five compose v, their distance 
apart being 62", p. 312. A more interesting double is /&, 
magnitudes five and five, distance 2.4", p. 158. Both 
stars are white, and they present a pretty appearance 
when the air is steady. They form a binary system of 
unknown period. 2 2078 (also called 17 Draconis) is a 
triple, magnitudes six, six and a half, and six, distances 
3.8", p. 116, and 90", p. 195. 2 1984 is an easy double, 
magnitudes six and a half and eight and a half, distance 
6.4", p. 276. The star rj is a very difficult double for even 
our largest aperture, on account of the faintness of one of 
its components. The magnitudes are two and a half and 
ten, distance 4.7", p. 140. Its near neighbor, 2 2054, may 
be a binary. Its magnitudes are six and seven, distance 
1", p. 0. In 2 2323 we have another triple, magnitudes 
five, eight and a half, and seven, distances 3.6", p. 360, 
and 90", p. 22, colors white, blue, and reddish. A fine 
double is e, magnitudes five and eight, distance 3", p. 5. 

The nebula No. 4373 is of a planetary character, and 
interesting as occupying the pole of the ecliptic. A few 
years ago Dr. Holden, with the Lick telescope, discovered 
that it is unique in its form. It consists of a double 
spiral, drawn out nearly in the line of sight, like the 
thread of a screw whose axis lies approximately endwise 
with respect to the observer. There is a central star, and 
another fainter star is involved in the outer spiral. The 
form of this object suggests strange ideas as to its origin. 
But the details mentioned are far beyond the reach of our 






94 PLEASURES OF THE TELESCOPE 

instruments. We shall only see it as a hazy speck. No. 
4415 is another nebula worth glancing at. It is Tuttle's 
so-called variable nebula. 

There are three constellations" represented on map 
No. 16 to which we shall pay brief visits. First Aquila 
demands attention. Its doubles may be summarized as 
follows: 11, magnitudes five and nine, distance 17.4", p. 
252; TT, magnitudes six and seven, distance 1.6", p. 122; 
23, magnitudes six and ten, distance 3.4", p. 12 requires 
the five-inch and good seeing; 57, magnitudes five and six, 
distance 36", p. 170; S 2654, magnitudes six and eight, 
distance 12", p. 234; 2 2644, magnitudes six and seven, 
distance 3.6", p. 208. 

The star rj is an interesting variable between magni- 
tudes three and a half and 4.7; period, seven days, four 
hours, fourteen minutes. The small red variable R 
changes from magnitude six to magnitude seven and a 
half and back again in a period of three hundred and fifty- 
one days. 

Star cluster No. 4440 is a striking object, its stars 
ranging from the ninth down to the twelfth magnitude. 

Just north of Aquila is the little constellation Sagitta, 
containing several interesting doubles and many fine star 
fields, which may be discovered by sweeping over it with a 
low-power eyepiece. The star f is double, magnitudes 
five and nine, distance 8.6", p. 312. The larger star is 
itself double, but far too close to be split, except with very 
large telescopes. In 6 we find three components of mag- 
nitudes seven, nine, and eight respectively, distances 11.4", 
p. 327, and 70", p. 227. A wide double is e magnitudes 
six and eight, distance 92", p. 81. Nebula No. 4572 is 
planetary. 

Turning to Delphinus, we find a very beautiful double 
in 7, magnitudes four and five, distance 11", p. 273, colors 



VULPECULA 



HERCULES 



DELPHINUS 



AQUARIUS 



AQUILA 



CAPRICORNUS 



SAGITTARIUS 



MAP No. 16. 



96 PLEASURES OF THE TELESCOPE 

golden and emerald. The leader a, which is not as bright 
as its neighbor /3, and which is believed to be irregularly 
variable, is of magnitude four, and has a companion of 
nine and a half magnitude at the 'distance 35", p. 278. 
At a similar distance, 35", p. 335, ft has an eleventh- 
magnitude companion, and the main star is also double, 
but excessively close, and much beyond our reach. It 
is believed to be a swiftly moving binary, whose stars are 
never separated widely enough to be distinguished with 
common telescopes. 



CHAPTER VI 

FROM LYRA TO ERIDANUS 

" This Orpheus struck when with his wdndrous song 
He charmed the woods and drew the rocks along. " MANTLIUS. 

WE resume our celestial explorations with the little 
constellation Lyra, whose chief star, Vega (a), has a very 
good claim to be regarded as the most beautiful in the 
sky. The position of this remarkable star is indicated in 
map No. 17. Every eye not insensitive to delicate shades 
of color perceives at once that Vega is not white, but blue- 
white. When the telescope is turned upon the star the 
color brightens splendidly. Indeed, some glasses decid- 
edly exaggerate the blueness of Vega, but the effect is so 
beautiful that one can easily forgive the optical imperfec- 
tion which produces it. With our four-inch we look for 
the well-known companion of Vega, a tenth-magnitude 
star, also of a blue color deeper than the hue of its great 
neighbor. The distance is 50", p. 158. Under the most 
favorable circumstances it might be glimpsed with the 
three-inch, but, upon the whole, I should regard it as too 
severe a test for so small an aperture. 

Vega is one of those stars which evidently are not only 
enormously larger than the sun (one estimate makes the 
ratio in this case nine hundred to one), but whose physical 
condition, as far as the spectroscope reveals it, is very dif- 
ferent from that of our ruling orb. Like Sirius, Vega dis- 
plays the lines of hydrogen most conspicuously, and it is 

97 



98 PLEASURES OF THE TELESCOPE 

probably a much hotter as well as a much more volumi- 
nous body than the sun. 

Close by, toward the east, two fourth-magnitude stars 
form a little triangle with Vega, f Both are interesting 
objects for the telescope, and the northern one, e, has few 
rivals in this respect. Let us first look at it with an opera 
glass. The slight magnifying power of such an instru- 
ment divides the star into two twinkling points. They 
are about two and a quarter minutes of arc apart, and 
exceptionally sharp-sighted persons are able to see them 
divided with the naked eye. Now take the three-inch tele- 
scope and look at them, with a moderate power. Each of 
the two stars revealed by the opera glass appears double, 
and a fifth star of the ninth magnitude is seen on one side 
of an imaginary line joining the two pairs. The northern- 
most pair is named e 1? the magnitudes being fifth and 
sixth, distance 3", p. 15. The other pair is e 2 , magnitudes 
fifth and sixth, distance 2.3", p. 133. Each pair is appar- 
ently a binary; but the period of revolution is unknown. 
Some have guessed a thousand years for one pair, and two 
thousand for the other. Another guess gives e l a period 
of one thousand years, and e 2 a period of eight hundred 
years. Hall, in his double-star observations, simply says 
of each, " A slow motion." 

Purely by guesswork a period has also been assigned 
to the two pairs in a supposed revolution around their 
common center, the time named being about a million 
years. It is not known, however, that such a motion ex- 
ists. Manifestly it could not be ascertained within the 
brief period during which scientific observations of these 
stars have been made. The importance of the element of 
time in the study of stellar motions is frequently over- 
looked, though not, of course, by those who are engaged 
in such work. The sun, for instance, and many of the 



100 PLEASURES OF THE TELESCOPE 

stars are known to be moving in what appear to be 
straight lines in space, but observations extending over 
thousands of years would probably show that these 
motions are in curved paths, and perhaps in closed 
orbits. 

If now in turn we take our four-inch glass, we shall see 
something else in this strange family group of e LyraB. 
Between 1 and e 2 , and placed one on each side of the join- 
ing line, appear two exceedingly faint specks of light, 
which Sir John Herschel made famous under the name of 
the debillissima. They are of the twelfth or thirteenth 
magnitude, and possibly variable to a slight degree. If 
you can not see them at first, turn your eye toward one 
side of the field of view, and thus, by bringing their images 
upon a more sensitive part of the retina, you may glimpse 
them. The sight is not much, yet it will repay you, as 
every glance into the depths of the universe does. 

The other fourth-magnitude star near Vega is f, a wide 
double, magnitudes fourth and sixth, distance 44", p. 
150. Below we find /3, another very interesting star, 
since it is both a multiple and an eccentric variable. It 
has four companions, three of which we can easily see 
with our three-inch; the fourth calls for the five-inch; the 
magnitudes are respectively four, seven or under, eight, 
eight and a half, and eleven; distances 45", p. 150; 65", 
p. 320; 85", p. 20; and 46", p. 248. The primary, 0, 
varies from about magnitude three and a half to magni- 
tude four and a half, the period being twelve days, twenty- 
one hours, forty-six minutes, and fifty-eight seconds. Two 
unequal maxima and minima occur within this period. In 
the spectrum of this star some of the hydrogen lines and 
the D 3 line (the latter representing helium, a constituent 
of the sun and of some of the stars, which, until its recent 
discovery in a few rare minerals was not known to exist 



FROM LYRA TO ERIDANUS 101 

on the earth) are bright, but they vary in visibility. More- 
over, dark lines due to hydrogen also appear in its spec- 
trum simultaneously with the bright lines of that ele- 
ment. Then, too, the bright lines are sometimes seen 
double. Professor Pickering's explanation is that @ Lyra3 
probably consists of two stars, which, like the two com- 
posing /? Auriga3, are too close to be separated with any 
telescope now existing, and that the body which gives the 
bright lines is revolving in a circle in a period of about 
twelve days and twenty-two hours around the body which 
gives the dark lines. He has also suggested that the ap- 
pearances could be accounted for by supposing a body 
like our sun to be rotating in twelve days and twenty-two 
hours, and having attached to it an enormous protuber- 
ance extending over more than one hundred and eighty 
degrees of longitude, so that when one end of it was 
approaching us with the rotation of the star the other 
end would be receding, and a splitting of the spectral 
lines at certain periods would be the consequence. " The 
variation in light," he adds, " may be caused by the visi- 
bility of a larger or smaller portion of this protuber- 
ance." 

Unfortunate star, doomed to carry its parasitical bur- 
den of hydrogen and helium, like Sindbad in the clasp 
of the Old Man of the Sea! Surely, the human imagina- 
tion is never so wonderful as when it bears an astronomer 
on its wings. Yet it must be admitted that the facts in 
this case are well calculated to summon the genius of 
hypothesis. And the puzzle is hardly simplified by Belo- 
polsky's observation that the body in & Lyra? giving dark 
hydrogen lines shows those lines also split at certain 
times. It has been calculated, from a study of the phe- 
nomena noted above, that the bright-line star in Lyrse is 
situated at a distance of about fifteen million miles from 



102 PLEASURES OF THE TELESCOPE 

the center of gravity of the curiously complicated system 
of which it forms a part. 

We have not yet exhausted the wonders of Lyra. On 
a line from /3 to 7, and about one" third of the distance 
from the former to the latter, is the celebrated King 
Nebula, indicated on the map by the number 4447. We 
need all the light we can get to see this object well, and 
so, although the three-inch will show it, we shall use the 
five-inch. Beginning with a power of one hundred diame- 
ters, which exhibits it as a minute elliptical ring, rather 
misty, very soft and delicate, and yet distinct, we in- 
crease the magnification first to two hundred and finally 
to three hundred, in order to distinguish a little better 
some of the details of its shape. Upon the whole, how- 
ever, we find that the lowest power that clearly brings 
out the ring gives the most satisfactory view. The 
circumference of the ring is greater than that of the 
planet Jupiter. Its ellipticity is conspicuous, the length 
of the longer axis being 78" and that of the shorter 60". 
Closely following the nebula as it moves through the field 
of view, our five-inch telescope reveals a faint star of the 
eleventh or twelfth magnitude, which is suspected of vari- 
ability. The largest instruments, like the Washington 
and the Lick glasses, have shown perhaps a dozen other 
stars apparently connected with the, nebula. A beautiful 
sparkling effect which the nebula presents was once 
thought to be an indication that it was really composed 
of a circle of stars, but the spectroscope shows that its 
constitution is gaseous. Just in the middle of the open 
ring is a feeble star, a mere spark in the most powerful 
telescope. But when the King Nebula is photographed 
and this is seen beautifully in the photographs made with 
the Crossley reflector on Mount Hamilton by the late Prof. 
J. E. Keeler this excessively faint star imprints its im- 



FROM LYRA TO ERIDANUS 103 

age boldly as a large bright blur, encircled by the nebu- 
lous ring, which itself appears to consist of a series of 
intertwisted spirals. 

Not far away we find a difficult double star, 17, whose 
components are of magnitudes six and ten or eleven, dis- 
tance 3.7", p. 325. 

From Lyra we pass to Cygnus, which, lying in one of 
the richest parts of the Milky Way, is a very interesting 
constellation for the possessor of a telescope. Its general 
outlines are plainly marked for the naked eye by the 
figure of a cross more than twenty degrees in length lying 
along the axis of the Milky Way. The foot of the cross is 
indicated by the star , also known as Albireo, one of the 
most charming of all the double stars. The three-inch 
amply suffices to reveal the beauty of this object, whose 
components present as sharp a contrast of light yellow 
and deep blue as it would be possible to produce artificially 
with the purest pigments. The magnitudes are three and 
seven, distance 34.6", p. 55. No motion has been de- 
tected indicating that these stars are connected in orbital 
revolution, yet no one can look at them without feeling 
that they are intimately related to one another. It is a 
sight to which one returns again and again, always with 
undiminished pleasure. The most inexperienced observer 
admires its beauty, and after an hour spent with doubtful 
results in trying to interest a tyro in double stars it is 
always with a sense of assured success that one turns the 
telescope to fi Cygni. 

Following up the beam of the imaginary cross along 
the current of the Milky Way, every square degree of 
which is here worth long gazing into, we come to a pair 
of stars which contend for the name-letter x- O n our 
map the letter is attached to the southernmost of the two, 
a variable of long period four hundred and six days 



104 PLEASURES OF THE TELESCOPE 

whose changes of brilliance lie between magnitudes four 
and thirteen, but which exhibits much irregularity in its 
maxima. The other star, not named but easily recognized 
in the map, is sometimes called IT. It is an attractive 
double whose colors faintly reproduce those of ft. The 
magnitudes are five and eight, distance 26", p. 73. 
Where the two arms of the cross meet is y, whose remark- 
able cortege of small stars running in curved streams 
should not be missed. Use the lowest magnifying power. 

At the extremity of the western arm of the cross is S, 
a close double, difficult for telescopes of moderate aper- 
ture on account of the difference in the magnitudes of the 
components. We may succeed in dividing it with the five- 
inch. The magnitudes are three and eight, distance 1.5", 
p. 310. It is regarded as a binary of long and as yet 
unascertained period. 

In o 2 we find a star of magnitude four and orange in 
color, having two blue companions, the first of magnitude 
seven and a half, distance 107", p. 174, and the second 
of magnitude five and a half, distance 358", p. 324. Far- 
ther north is ^, which presents to us the combination of 
a white five-and-a-half-magnitude star with a lilac star of 
magnitude seven and a half. The distance is 3", p. 184. 
A very pretty sight. 

We now pass to the extremity of the other arm of the 
cross, near which lies the beautiful little double 49, whose 
components are of magnitudes six and eight, distance 2.8", 
p. 50. The colors are yellow and blue, conspicuous and 
finely contrasted. A neighboring double of similar hues 
is 52, in which the magnitudes are four and nine, distance 
6", p. 60. Sweeping a little way northward we come 
upon an interesting binary, \, which is unfortunately be- 
yond the dividing power of our largest glass. A good 
seven-inch or seven-and-a-half-inch should split it under 



FROM LYRA TO ERIDANU8 105 

favorable circumstances. Its magnitudes are six and 
seven, distance 0.66", p. 74. 

The next step carries us to a very famous object, 61 
Cygni, long known as the nearest star in the northern 
hemisphere of the heavens. It is a double which our 
three-inch will readily divide, the magnitudes being both 
six, distance 21", p. 122. The distance of 61 Cygni, accord- 
ing to Hall's parallax of 0.27", is about 70,000,000,000,000 
miles. There is some question whether or not it is a 
binary, for, while the twin stars are both moving in the 
same direction in space with comparative rapidity, yet 
conclusive evidence of orbital motion is lacking. When 
one has noticed the contrast in apparent size between this 
comparatively near-by star, which the naked eye only 
detects with considerable difficulty, and some of its bril- 
liant neighbors whose distance is so great as to be im- 
measurable with our present means, no better proof will 
be needed of the fact that the faintness of a star is not 
necessarily an indication of remoteness. 

We may prepare our eyes for a beautiful exhibition of 
contrasted colors once more in the star /*. This is really 
a quadruple, although only two of its components are 
close and conspicuous. The magnitudes are five, six, 
seven and a half, and twelve; distances 2.4", p, 121; 208", 
p. 56; and 35", p. 264. The color of the largest star is 
white and that of its nearest companion blue; the star of 
magnitude seven and a half is also blue. 

The star cluster 4681 is a fine sight with our largest 
glass. In the map we find the place marked where the 
new star of 1876 made its appearance. This was first 
noticed on November 24, 1876, when it shone with the 
brilliance of a star of magnitude three and a half. Its 
spectrum was carefully studied, especially by Vogel, and 
the very interesting changes that it underwent were 

8 



106 PLEASURES OF THE TELESCOPE 

noted. Within a year the star had faded to less than 
the tenth magnitude, and its spectrum had completely 
changed in appearance, and had come to bear a close re- 
semblance to that of a planetary nebula. This has been 
quoted as a possible instance of a celestial collision 
through whose effects the solid colliding masses were 
vaporized and expanded into a nebula. At present the 
star is very faint and can only be seen with the most 
powerful telescopes. Compare with the case of Nova 
Auriga?, previously discussed. 

Underneath Cygnus we notice the small constellation 
Vulpecula. It contains a few objects worthy of attention, 
the first being the nebula 4532, the " dumb-bell nebula " 
of Lord Eosse. With the four-inch, and better with the 
five-inch, we are able to perceive that it consists of two 
close-lying tufts of misty light. Many stars surround it, 
and large telescopes show them scattered between the 
two main masses of the nebula. The Lick photographs 
show that its structure is spiral. The star 11 points out 
the place where a new star of the third magnitude ap- 
peared in 1670. 2 2695 is a close double, magnitudes six 
and eight, distance 0.96", p. 78. 

We turn to map No. 18, and, beginning at the western 
end of the constellation Aquarius, we find the variable T, 
which ranges between magnitudes seven and thirteen in 
a period of about two hundred and three days. Its near 
neighbor 2 2729 is a very close double, beyond the sepa- 
rating power of our five-inch, the magnitudes being six 
and seven, distance 0.6", p. 176. 2 2745, also known as 
12 Aquarii, is a good double for the three-inch. Its mag- 
nitudes are six and eight, distance 2.8", p. 190. In we 
discover a beauty. It is a slow binary of magnitudes four 
and four, distance 3.1", p. 321. According to some ob- 
servers both stars have a greenish tinge. The star 41 is a 



108 PLEASURES OF THE TELESCOPE 

wider double, magnitudes six and eight, distance 5", p. 
115, colors yellow and blue. The uncommon stellar con- 
trast of white with light garnet is exhibited by T, mag- 
nitudes six and nine, distance 27", p. 115. Yellow and 
blue occur again conspicuously in ^, magnitudes four and 
a half and eight and a half, distance 50", p. 310. Kose 
and emerald have been recorded as the colors exhibited 
in 2 2998, whose magnitudes are five and seven, distance 
1.3", p. 346. 

The variables S and R are both red. The former 
ranges between magnitudes eight and twelve, period two 
hundred and eighty days, and the latter between magni- 
tudes six and eleven, period about three hundred and 
ninety days. 

The nebula 4628 is Kosse's " Saturn nebula," so called 
because with his great telescope it presented the appear- 
ance of a nebulous model of the planet Saturn. With our 
five-inch we see it simply as a planetary nebula. We may 
also glance at another nebula, 4678, which appears circu- 
lar and is pinned with a little star at the edge. 

The small constellation Equuleus contains a surpris- 
ingly large number of interesting objects. 2 2735 is a 
rather close double, magnitudes six and eight, distance 
1.8", p. 287. 2 2737 (the first star to the left of 2 2735, 
the name having accidentally been omitted from the map) 
is a beautiful triple, although the two closest stars, of 
magnitudes six and seven, can not be separated by our 
instruments. Their distance in 1886 was 0.78", p. 286, 
and they had then been closing rapidly since 1884, when the 
distance was 1.26". The third star, of magnitude eight, is 
distant 11", p. 75. 2 2744 consists of two stars, mag- 
nitudes six and seven, distance 1.4", p. 1.67. It is prob- 
ably a binary, 2 2742 is a wider double, magnitudes both 
six, distance 2.6", p. 225. Another triple, one of whose 



FROM LYRA TO ERIDANUS 109 

components is beyond our reach, is 7. Here the mag- 
nitudes are fifth, twelfth, and sixth, distances 2", p. 274 
and 366". It would also be useless for us to try to sepa- 
rate S, but it is interesting to remember that this is one 
of the closest of known double stars, the magnitudes 
being fourth and fifth, distance 0.4", p. 198. These data 
are from HalPs measurements in 1887. The star is, no 
doubt, a binary. With the five-inch we may detect one 
and perhaps two of the companion stars in the quadruple 
/3. The magnitudes are five, ten, and two eleven, dis- 
tances 67", p. 309; 86", p. 276; and 6.5", p. 15. The 
close pair is comprised in the tenth-magnitude star. 

Map No. 19 introduces us to the constellation Pegasus, 
which is comparatively barren to the naked eye, and by no 
means rich in telescopic phenomena. The star e, of mag- 
nitude two and a half, has a blue companion of the eighth 
magnitude, distance 138", p. 324; colors yellow and 
violet. A curious experiment that may be tried with this 
star is described by Webb, who ascribes the discovery of 
the phenomenon to Sir John Herschel. When near the 
meridian the small star in e appears, in the telescope, 
underneath the large one. If now the tube of the tele- 
scope be slightly swung from side to side the small star 
will appear to describe a pendulumlike movement with 
respect to the large one. The explanation suggested is 
that the comparative faintness of the small star causes 
its light to affect the retina of the eye less quickly than 
does that of its brighter companion, and, in consequence, 
the reversal of its apparent motion with the swinging of 
the telescope is not perceived so soon. 

The third-magnitude star ^ has a companion of mag- 
nitude ten and a half, distance 90", p. 340. The star /?, 
of the second magnitude, and reddish, is variable to the 
extent of half a magnitude in an irregular period, and 7. 



FROM LYRA TO ERIDANU8 HI 

of magnitude two and a half, has an eleventh-magnitude 
companion, distance 162", p. 285. 

Our interest is revived on turning, with the guidance 
of map No. 20, from the comparative poverty of Pegasus 
to the spacious constellation Cetus. The first double star 
that we meet in this constellation is 26, whose compo- 
nents are of magnitudes six and nine, distance 16.4", 
p. 252; colors, topaz and lilac. Not far away is the 
closer double 42, composed of a sixth and a seventh mag- 
nitude star, distance 1.25", p. 350. The four-inch is 
capable of splitting this star, but we shall do better to 
use the five-inch. In passing we may glance at the tenth- 
magnitude companion to 97, distance 225", p. 304. An- 
other wide pair is found in ?, magnitudes three and nine, 
distance 185", p. 40. 

The next step brings us to the wonderful variable o, 
or Mira, whose changes have been watched for three 
centuries, the first observer of the variability of the star 
having been David Fabricius in 1596. Not only is the 
range of variability very great, but the period is remark- 
ably irregular. In the time of Hevelius, Mira was once 
invisible for four years. When brightest, the star is of 
about the second magnitude, and when faintest, of the 
ninth magnitude, but at maximum it seldom exhibits the 
greatest brilliance that it has on a few occasions shown 
itself capable of attaining. Ordinarily it begins to fade 
after reaching the fourth or fifth magnitude. The period 
averages about three hundred and thirty-one days, but is 
irregularly variable to the extent of twenty-five days. Its 
color is red, and its spectrum shows bright lines, which it 
is believed disappear when the star sinks to a minimum. 
Among the various theories proposed to account for such 
changes as these the most probable appears to be that 
which ascribes them to some cause analogous to that 



FROM LYEA TO ERIDANUS 113 

operating in the production of sun spots. The outburst 
of light, however, as pointed out by Schemer, should be 
regarded as corresponding to the maximum and not the 
minimum stage of sun-spot activity. According to this 
view, the star is to be regarded as possessing an extensive 
atmosphere of hydrogen, which, during the maximum, is 
upheaved into enormous prominences, and the brilliance 
of the light from these prominences suffices to swamp the 
photospheric light, so that in the spectrum the hydrogen 
lines appear bright instead of dark. 

It is not possible to suppose that Mira can be the 
center of a system of habitable planets, no matter what 
we may think of the more constant stars in that regard, 
because its radiation manifestly increases more than six 
hundred fold, and then falls off again to an equal extent 
once in every ten or eleven months. I have met people 
who can not believe that the Almighty would make a sun 
and then allow its energies " to go to waste," by not sup- 
plying it with a family of worlds. But I imagine that if 
they had to live within the precincts of Mira Ceti they 
would cry out for exemption from their own law of stellar 
utility. 

The most beautiful double star in Cetus is y, magni- 
tudes three and seven, distance 3", p. 288; hues, straw- 
color and blue. The leading star a, of magnitude two and 
a half, has a distant blue companion three magnitudes 
fainter, and between them are two minute stars, the 
southernmost of which is a double, magnitudes both 
eleven, distance 10", p. 225. 

The variable S ranges between magnitudes seven and 
twelve in a somewhat irregular period of about eleven 
months, while K ranges between the seventh and the thir- 
teenth magnitudes in a period of one hundred and sixty- 
seven days. 



114 PLEASURES OF THE TELESCOPE 

The constellation Eridanus, represented in map No. 21, 
contains a few fine double stars, one of the most interest- 
ing of which is 12, a rather close binary. The magnitudes 
are four and eight, distance 2", p.' 327. We shall take 
the five-inch for this, and a steady atmosphere and sharp 
seeing will be necessary on account of the wide difference 
in the brightness of the component stars. Amateurs fre- 
quently fail to make due allowance for the effect of such 
difference. When the limit of separating power for a 
telescope of a particular aperture is set at 1" or 2", as the 
case may be, it is assumed that the stars composing the 
doubles on which the test is made shall be of nearly the 
same magnitude, or at least that they shall not differ by 
more than one or two magnitudes at the most. The stray 
light surrounding a comparatively bright star tends to 
conceal a faint companion, although the telescope may 
perfectly separate them so far as the stellar disks are con- 
cerned. Then, too, I have observed in my own experience 
that a very faint and close double is more difficult than a 
brighter pair not more widely separated, usually on ac- 
count of the defect of light, and this is true even when 
the components of the faint double are of equal mag- 
nitude. 

2 470, otherwise known as 32 Eridani, is a superb 
object on account of the colors of its components, the 
larger star being a rich topaz and the smaller an ultra- 
marine; while the difference in magnitude is not as great 
as in many of the colored doubles. The magnitudes are 
five and seven, distance 6.7", p. 348. The star y, of mag- 
nitude two and a half, has a tenth-magnitude companion, 
distant 51", p. 238. S 516, also called 39 Eridani, con- 
sists of two stars of magnitudes six and nine, distance 
6.4", p. 150; colors, yellow and blue. The supposed 
binary character of this star has not yet been established. 



116 PLEASURES OF THE TELESCOPE 

In o 2 we come upon an interesting triple star, two of 
whose components at any rate we can easily see. The 
largest component is of 'the fourth magnitude. At a dis- 
tance of 82", p. 105, we find a fenth-magnitude com- 
panion. This companion is itself double, the magnitudes 
of its components being ten and eleven, distance 2.6", 
p. 98. Hall says of these stars that they " form a re- 
markable system." He has also observed a fourth star 
of the twelfth magnitude, distant 45" from the largest 
star, p. 85. This is apparently unconnected with the 
others, although it is only half as distant as the tenth- 
magnitude component is from the primary. 2 590 is in- 
teresting because of the similarity of its two components 
in size, both being of about the seventh magnitude, dis- 
tance 10", p. 318. 

Finally, we turn to the nebula 826. This is planetary 
in form and inconspicuous, but Lassell has described it as 
presenting a most extraordinary appearance with his 
great reflector a circular nebula lying upon another 
fainter and larger nebula of a similar shape, and having a 
star in its center. Yet it may possibly be an immensely 
distant star cluster instead of a nebula, since its spectrum 
does not appear to be gaseous. 



CHAPTER VII 

PISCES, ARIES, TAURUS, AND THE NORTHERN STARS 

' ' Now sing we stormy skies when Autumn weighs 
The year, and adds to nights and shortens days, 
And suns declining shine with feeble rays." DRYDEN'S VIRGIL. 

THE eastern end of Pisces, represented in map No. 22, 
includes most of the interesting telescopic objects that 
the constellation contains. We begin our exploration at 
the star numbered 55, a double that is very beautiful when 
viewed with the three-inch glass. The components are of 
magnitudes five and eight, distance 6.6", p. 192. The larger 
star is yellow and the smaller deep blue. The star 65, while 
lacking the peculiar charm of contrasted colors so finely 
displayed in 55, possesses an attraction in the equality of 
its components which are both of the sixth magnitude and 
milk-white. The distance is 4.5", p. 118. In 66 we find a 
swift binary whose components are at present far too 
close for any except the largest telescopes. The distance 
in 1894 was only 0.36", p. 329. The magnitudes are six 
and seven. In contrast with this excessively close double 
is -fr, whose components are both of magnitude five and a 
half, distance 30", p. 160. Dropping down to 77 we come 
upon another very wide and pleasing double, magnitudes 
six and seven, distance 33", p. 82, colors white and lilac 
or pale blue. Hardly less beautiful is f, magnitudes five 
and six, distance 24", p. 64. Finest of all is a, which ex- 
hibits a remarkable color contrast, the larger star being 

117 



118 PLEASURES OF THE TELESCOPE 

greenish and the smaller blue. The magnitudes are four 
and five, distance 3", p. 320. This star is a binary, but 
the motion is slow. The variable K ranges between mag- 
nitudes seven and thirteen, period three hundred and 
forty-four days. 

The constellation Aries contains several beautiful 
doubles, all but one of which are easy for our smallest 
aperture. The most striking of these is 7, which is his- 
torically interesting as the first double star discovered. 
The discovery was made by Robert Hooke in 1664 by acci- 
dent, while he was following the comet of that year with 
his telescope. He expressed great surprise on noticing 
that the glass divided the star, and remarked that he had 
not met with a like instance in all the heavens. His ob- 
servations could not have been very extensive or very 
carefully conducted, for there are many double stars much 
wider than 7 Arietis which Hooke could certainly have 
separated if he had examined them. The magnitudes of 
the components of 7 are four and four and a half, or, 
according to Hall, both four; distance 8.5", p. 180. A 
few degrees above 7, passing by /3, is a wide double X, 
magnitudes five and eight, distance 37", p. 45, colors 
white and lilac or violet. Three stars are to be seen in 
14: magnitudes five and a half, ten, and nine, distances 
83", p. 36, and 106", p. 278, colors white, blue, and lilac. 
The star 30 is a very pretty double, magnitudes six and 
seven, distance 38.6", p. 273. 2 289 consists of a topaz 
star combined with a sapphire, magnitudes six and nine, 
distance 28.5", p. 0. The fourth-magnitude star 41 has 
several faint companions. The magnitudes of two of 
these are eleven and nine, distances 34", p. 203, and 130", 
p. 230. We discover another triple in TT, magnitudes five, 
eight, and eleven, distances 3.24", p. 122, and 25", p. 110. 
The double mentioned above as being too close for our 



120 PLEASURES OF THE TELESCOPE 

three-inch glass is e, which, however, can be divided with 
the four-inch, although the five-inch will serve us better. 
The magnitudes are five and a half and six, distance 1.26", 
p. 202. The star 52 has two companions, one of which 
is so close that our instruments can not separate it, while 
the other is too faint to be visible in the light of its bril- 
liant neighbor without the aid of a very powerful tele- 
scope. 

We are now about to enter one of the most magnificent 
regions in the sky, which is hardly less attractive to the 
naked eye than Orion, and which men must have admired 
from the beginning of their history on the earth, the con- 
stellation Taurus (map No. 23). Two groups of stars 
especially distinguish Taurus, the Hyades and the Plei- 
ades, and both are exceedingly interesting when viewed 
with the lowest magnifying powers of our telescopes. 

We shall begin with a little star just west of the 
Pleiades, 2 412, also called 7 Tauri. This is a triple, but 
we can see it only as a double, the third star being ex- 
ceedingly close to the primary. The magnitudes are six 
and a half, seven, and ten, distances 0.3", p. 216, and 22", 
p. 62. In the Pleiades we naturally turn to the brightest 
star 97, or Alcyone, famous for having once been regarded 
as the central sun around which our sun and a multitude 
of other luminaries were supposed to revolve, and pic- 
turesque on account of the little triangle of small stars 
near it which the least telescopic assistance enables us 
to see. One may derive much pleasure from a study of 
the various groupings of stars in the Pleiades. Photog- 
raphy has demonstrated, what had long been suspected 
from occasional glimpses revealed by the telescope, that 
this celebrated cluster of stars is intermingled with curi- 
ous forms of nebulae. The nebulous matter appears in 
festoons, apparently attached to some of the larger stars, 



122 PLEASURES OF THE TELESCOPE 

such as Alcyone, Merope, and Maia, and in long, narrow, 
straight lines, the most remarkable of which, a faintly 
luminous thread starting midway between Maia and Alcy- 
one and running eastward some 40*, is beaded with seven 
or eight stars. The width of this strange nebulous streak 
is, on an average, 3" or 4", and there is, perhaps, no more 
wonderful phenomenon anywhere in celestial space. Un- 
fortunately, no telescope is able to show it, and all our 
knowledge about it is based upon photographs. It might 
be supposed that it was a nebulous disk seen edgewise, 
but for the fact that at the largest star involved in its 
course it bends sharply about 10 out of its former direc- 
tion, and for the additional fact that it seems to take its 
origin from a curved offshoot of the intricate nebulous 
mass surrounding Maia. Exactly at the point where this 
curve is transformed into a straight line shines a small 
star! In view of all the facts the idea does not seem to 
be very far-fetched that in the Pleiades we behold an as- 
semblage of suns, large and small, formed by the gradual 
condensation of a nebula, and in which evolution has gone 
on far beyond the stage represented by the Orion nebula, 
where also a group of stars may be in process of forma- 
tion out of nebulous matter. If we look a little farther 
along this line of development, we may perceive in such 
a stellar assemblage as the cluster in Hercules, a still 
later phase wherein all the originally scattered material 
has, perhaps, been absorbed into the starry nuclei. 

The yellow star 2 430 has two companions: magni- 
tudes six, nine, and nine and a half, distances 26", p. 55, 
and 39", p. 302. The star 30 of the fifth magnitude has a 
companion of the ninth magnitude, distance 9", p. 58, 
colors emerald and purple, faint. An interesting vari- 
able, of the type of Algol, is X, which at maximum is of 
magnitude three and four tenths and at minimum of mag- 



PISCES, ARIES, TAURUS, AND THE NORTHERN STARS 123 

nitude four and two tenths. Its period from one maxi- 
mum to the next is about three days and twenty-three 
hours, but the actual changes occupy only about ten 
hours, and it loses light more swiftly than it regains it. 
A combination of red and blue is presented by < (mis- 
takenly marked on map No. 23 as ^). The magnitudes 
are six and eight, distance 56", p. 242. A double of simi- 
lar magnitudes is %, distance 19", p. 25. Between the 
two stars which the naked eye sees in K is a minute pair, 
-each of less than the eleventh magnitude, distance 5", p. 
324. Another naked-eye double is formed by 1 and 2 , in 
the Hyades. The magnitudes are five and five and a half, 
distance about 5' 37". 

The leading star of Taurus, Aldebaran (a), is celebrated 
for its reddish color. The precise hue is rather uncertain, 
but Aldebaran is not orange as Betelgeuse in Orion is, 
and no correct eye can for an instant confuse the colors 
of these two stars, although many persons seem to be un- 
able to detect the very plain difference between them in 
this respect. Aldebaran has been called " rose-red," and 
it would be an interesting occupation for an amateur to 
determine, with the aid of some proper color scale, the 
precise hue of this star, and of the many other stars which 
exhibit chromatic idiosyncrasy. Aldebaran is further in- 
teresting as being a standard first-magnitude star. With 
the four-inch glass we see without difficulty the tenth- 
magnitude companion following Aldebaran at a distance 
of 114", p. 35. There is an almost inexplicable charm 
about these faint attendants of bright stars, which is 
quite different from the interest attaching to a close and 
nearly equal pair. The impression of physical relation- 
ship is never lacking though it may be deceptive, and this 
awakens a lively appreciation of the vast differences of 
magnitude that exist among the different suns of space. 



124 PLEASURES OF THE TELESCOPE 

The actual size and might of this great red sun form 
an attractive subject for contemplation. As it appears to 
our eyes Aldebaran gives one twenty-five-thousand-mil- 
lionth as much light as the sun, but' if we were placed mid- 
way between them the star would outshine the sun in the 
ratio of not less than 160 to 1. And yet, gigantic as it 
is, Aldebaran is possibly a pygmy in comparison with 
Arcturus, whose possible dimensions were discussed in 
the chapter relating to Bootes. Although Aldebaran is 
known to possess several of the metallic elements that 
exist in the sun, its spectrum differs widely from the solar 
spectrum in some respects, and more closely resembles 
that of Arcturus. 

Other interesting objects in Taurus are <r, divisible 
with the naked eye, magnitudes five and five and a half, 
distance 7'; 2 674, double, magnitudes six and nine, dis- 
tance 10.5", p. 147; S 716, double, magnitudes six and 
seven, distance 5", p. 200 a pleasing sight; T, triple, 
magnitudes four, ten and a half, and eleven, distances 36", 
p. 249, and 36", p. 60 the ten-and-a-half-magnitude 
star is itself double, as discovered by Burnham; star clus- 
ter No. 1030, not quite as broad as the moon, and contain- 
ing some stars as large as the eleventh magnitude; and 
nebula No. 1157, the so-called " Crab nebula " of Lord 
Rosse, which our glasses will show only as a misty patch 
of faint light, although large telescopes reveal in it a 
very curious structure. 

We now turn to the cluster of circumpolar constella- 
tions sometimes called the Royal Family, in allusion to 
the well-known story of the Ethiopian king Cepheus and 
his queen Cassiopeia, whose daughter Andromeda was 
exposed on the seashore to be devoured by a monster, but 
who was saved by the hero Perseus. All these mythologic 
personages are represented in the constellations that we 



PISCES, ARIES, TAURUS, AND THE NORTHERN STARS 125 

are about to study.* We begin with Andromeda (map No. 
24). The leading star a marks one corner of the great 
square of Pegasus. The first star of telescopic interest 
that we find in Andromeda is /A, a double difficult on ac- 
count of the faintness of the smaller component. The 
magnitudes are four and eleven, distance 49", p. 110. A 
few degrees north of /* the naked eye detects a glimmer- 
ing point where lies the Great Nebula in Andromeda. 
This is indicated on the map by the number 116. With 
either of our three telescopes it is an interesting object, 
but of course it is advisable to use our largest glass in 
order to get as much light as possible. All that we can 
see is a long, shuttle-shaped nebulous object, having a 
brighter point near the center. Many stars are scattered 
over the field in its neighborhood, but the nebula itself, 
although its spectrum is peculiar in resembling that of a 
faint star, is evidently a gaseous or at any rate a meteo- 
ritic mass, since photographs show it to be composed of a 
series of imperfectly separated spirals surrounding a vast 
central condensation. This peculiarity of the Androm- 
eda nebula, which is invisible with telescopes although 
conspicuous in the photographs, has, since its discovery 
a few years ago, given a great impetus to speculation con- 
cerning the transformation of nebula into stars and star 
clusters. No one can look at a good photograph of this 
wonderful phenomenon without noticing its resemblance 
to the ideal state of things which, according to the nebu- 
lar hypothesis, must once have existed in the solar system. 
It is to be remembered, however, that there is probably 
sufficient material in the Andromeda nebula to make a 
system many times, perhaps hundreds or thousands of 
times, as extensive as that of which our sun is the center. 
If one contemplates this nebula only long enough to get 

* For further details on this subject see Astronomy with an Opera-glass. 



126 



PLEASURES OF THE TELESCOPE 



a clear perception of the fact that creation was not ended 
when, according to the Mosaic history, God, having in six 
days finished " the heavens and the earth and all the host 
of them," rested from all his work, a good blow will have 
been dealt for the cause of truth. Systems far vaster 
than ours are now in the bud, and long before they have 
bloomed, ambitious man, who once dreamed that all these 



ASTEROPE II 



TAYGETA* 



ALCYONE 

* " 



ELECTRA * 



THE CHIEF STARS IN THE PLEIADES. 



things were created to serve him, will probably have van- 
ished with the extinguishment of the little star whose 
radiant energy made his life and his achievements briefly 
possible. 

In August, 1885, -a new star of magnitude six and a 
half made its appearance suddenly near the center of the 
Andromeda nebula. Within one year it had disappeared, 
having gradually dwindled until the great Washington 
telescope, then the largest in use, no longer showed it. 
That this was a phenomenon connected with the nebula 
is most probable, but just what occurred to produce it no- 
body knows. The observed appearances might have been 



128 PLEASURES OF THE TELESCOPE 

produced by a collision, and no better hypothesis has yet 
been suggested to account for them. 

Near the opposite end of the constellation from a we 
find the most interesting of triple stars in 7. The two 
larger components of this beautiful star are of magni- 
tudes three and six, distance 10", colors golden yellow and 
deep blue. The three-inch shows them finely. The smaller 
star is itself double, its companion being of magnitude 
eight, distance when discovered in 1842 0.5", color bluish 
green. A few years ago this third star got so close to its 
primary that it was invisible even with the highest powers 
of the great Lick telescope, but at present it is widening 
again. In October, 1893, I had the pleasure of looking 
at 7 Andromedse with the Lick telescope, and at that time 
it was possible just to separate the third star. The 
angle seemed too small for certain measurement, but 
a single setting of the micrometer by Mr. Barnard, to 
whose kindness I was indebted for my view of the star, 
gave 0.17" as the approximate distance. In 1900 the dis- 
tance had increased to 0.4", p. 115. The brilliance of 
color contrast between the two larger stars of 7 Androm- 
eda3 is hardly inferior to that exhibited in Cygni, so 
that this star may be regarded as one of the most pictur- 
esque of stellar objects for small telescopes. 

Other pleasing objects in this constellation are the 
binary star 36, magnitudes six and six and a half, distance 
1", p. 17 the two stars are slowly closing and the five- 
inch glass is required to separate them: the richly col- 
ored variable B, which fades from magnitude five and a 
half to invisibility, and then recovers its light in a period 
of about four hundred and five days; and the bright star 
cluster 457, which covers a space about equal to the area 
of the full moon. 

Just south of the eastern end of Andromeda is the 



PISCES, ARIES, TAURUS, AND THE NORTHERN STARS 129 

small constellation Triangulum, or the Triangles, contain- 
ing two interesting objects. One of these is the beautiful 
little double 6, magnitudes five and six, distance 3.8", 
p. 77, colors yellow and blue; and the other, the nebula 
352, which equals in extent the star cluster in Andromeda 
described above, but nevertheless appears very faint with 
our largest glass. Its faintness, however, is not an indi- 
cation of insignificance, for to very powerful 'telescopes 
it exhibits a wonderful system of nuclei and spirals an- 
other bit of chaos that is yielding by age-long steps to the 
influence of demiurgic forces. 

A richer constellation than Andromeda, both for 
naked-eye and telescopic observation, is Perseus, which is 
especially remarkable for its star clusters. Two of these, 
512 and 521, constitute the celebrated double cluster, 
sometimes called the Sword-hand of Perseus, and also % 
Persei. To the smallest telescope this aggregation of 
stars, ranging in magnitude from six and a half to four- 
teen, and grouped about two neighboring centers, pre- 
sents a marvelous appearance. As an educative object 
for those unaccustomed to celestial observations it may 
be compared among star clusters to Cygni among 
double stars, for the most indifferent spectator is struck 
with wonder in viewing it. All the other clusters in 
Perseus represented on the map are worth examining, 
although none of them calls for special mention, except 
perhaps 584, where we may distinguish at least a hundred 
separate stars within an area less than one quarter as 
expansive as the face of the moon. 

Among the double stars of Perseus we note first 77, 
whose components are of magnitudes four and eight, dis- 
tance 28", colors white and pale blue. The double e is 
especially interesting on account of an alleged change of 
color from blue to red which the smaller star undergoes 






130 PLEASURES OF THE TELESCOPE 

coincidently with a variation of brightness. The mag- 
nitudes are three and eight, distance 9", p. 9. An inter- 
esting multiple is f, two of whose stars at least we can 
see. The magnitudes are three, nine, ten, and ten, dis- 
tances 13", p. 207, 90", and 112". 

The chief attraction in Perseus is the changeful and 
wonderful /3, or Algol, the great typical star among the 
short-period variables. During the greater part of its 
period this star is of magnitude two and two tenths, but 
for a very short time, following a rapid loss of light, it 
remains at magnitude three and seven tenths. The differ- 
ence, one magnitude and a half, corresponds to an actual 
difference in brightness in the ratio of 3.75 to 1. The 
entire loss of light during the declension occupies only 
four hours and a half. The star remains at its faintest 
for a few minutes only before a perceptible gain of light 
occurs, and the return to maximum is as rapid as was 
the preceding decline. The period from one minimum to 
the next is two days twenty hours forty-eight minutes 
fifty-three seconds, with an irregularity amounting to a 
few seconds in a year. The Arabs named the star Algol, 
or the Demon, on account of its eccentricity which did not 
escape their attention; and when Goodricke, in 1782, ap- 
plied a scientific method of observation to it, the real 
cause of its variations was suggested by him, but his ex- 
planation failed of general acceptance until its truth was 
established by Prof. E. C. Pickering in 1880. This expla- 
nation gives us a wonderful insight into stellar consti- 
tution. According to it, Algol possesses a companion as 
large as the sun, but invisible, both because of its proxim- 
ity to that star and because it yields no light, and revolv- 
ing in a plane horizontal to our line of sight. The period 
of revolution is identical with the period of AlgoFs cycle 
of variation, and the diminution of light is caused by the 



PISCES, ARIES, TAURUS, AND THE NORTHERN STARS 131 

interposition of the dark body as it sweeps along that 
part of its orbit lying between our point of view and the 
disk of Algol. In other words, once in every two days 
twenty hours and forty-nine minutes Algol, as seen from 
the earth, undergoes a partial eclipse. 

In consequence of the great comparative mass of its 
dark companion, Algol itself moves in an orbit around 
their common center with a velocity quite sufficient to be 
detected by the shifting of the lines in its spectrum. By 
means of data thus obtained the mass, size, and distance 
apart of Algol and its singular comrade have been in- 
ferred. The diameter of Algol is believed to be about 
1,125,000 miles, that of the dark body about 840,000 miles, 
and the mean distance from center to center 3,230,000 
miles. The density of both the light and the dark star is 
slight compared with that of the sun, so that their com- 
bined mass is only two thirds as great as the sun's. 

Mention has been made of a slight irregularity in 
AlgoFs period of variation. Basing his calculations upon 
this inequality, Dr. Chandler has put forward the hypoth- 
esis that there is another invisible body connected with 
Algol, and situated at a distance from $t of about 
1,800,000,000 miles, and that around this body, which is 
far more massive than the others, Algol and its compan- 
ions revolve in a period of one hundred and thirty years! 
Dr. Chandler has earned the right to have his hypotheses 
regarded with respect, even when they are as extraor- 
dinary as that which has just been described. It needs no 
indulgence of the imagination to lend interest to Algol; 
the simple facts are sufficient. How did that bright star 
fall in with its black neighbors? Or were they created 
together? 

Passing to the region covered by map No. 25, our eyes 
are caught by the curious figure, formed by the five bright- 



132 PLEASURES OF THE TELESCOPE 

est stars of the constellation Cassiopeia, somewhat re- 
sembling the letter W. Like Perseus, this is a rich con- 
stellation, both in star clusters and double stars. Among 
the latter we select as our first example cr, in which we 
find a combination of color that is at once very unusual 
and very striking green and blue. The magnitudes are 
five and seven, distance 3", p. 324. Another beautiful 
colored double is 77, whose magnitudes are four and seven 
and a half, distance 5", p. 200, colors white and purple. 
This is one of the comparatively small number of stars 
the measure of whose distance has been attempted, and a 
keen sense of the uncertainty of such measures is con- 
veyed by the fact that authorities of apparently equal 
weight place 17 Cassiopeia at such discordant distances 
as 124,000,000,000,000 miles, 70,000,000,000,000 miles, and 
42,000,000,000,000 miles. It will be observed that the dif- 
ference between the greatest and the least of these esti- 
mates is about double the entire distance given by the 
latter. The same thing is practically true of the various 
attempts to ascertain the distance of the other stars 
which have a perceptible parallax, even those which are 
evidently the nearest. In some cases the later measures 
increase the distance, in other cases they diminish it; in 
no case is there anything like a complete accord. Yet of 
course we are not to infer that it is hopeless to learn any- 
thing about the distances of the stars. With all their 
uncertainties and disagreements the few parallaxes we 
possess have laid a good foundation for a knowledge of 
the dimensions of at least the nearer parts of the universe. 
We find an interesting triple in 1^, the magnitudes of 
the larger components being four and a half and eight and 
a half, distance 30". The smaller star has a nine-and-a- 
half-magnitude companion, distance 3". A more beauti- 
ful triple is i, magnitudes four, seven, and eight, distances 



134: PLEASURES OF THE TELESCOPE 

2", p. 256, and 7.5", p. 112. Cassiopeia contains many 
star clusters, three of which are indicated in the map. Of 
these 392 is perhaps the most interesting, as it includes 
stars of many magnitudes, among- which are a red one 
of the eighth magnitude, and a ninth-magnitude double 
whose components are 8" apart. Not far from the star K 
we find the spot where the most brilliant temporary star 
on record made its appearance on November 11, 1572. Ty- 
cho Brahe studied this phenomenon during the entire 
period of its visibility, which lasted until March, 1574. It 
burst out suddenly with overpowering splendor, far out- 
shining every fixed star, and even equaling Venus at her 
brightest. In a very short time it began to fade, regu- 
larly diminishing in brightness, and at the same time 
undergoing changes of color, ending in red, until it disap- 
peared. It has never been seen since, and the suspicion 
once entertained that it was a variable with a period con- 
siderably exceeding three hundred years has not been con- 
firmed. There is a tenth-magnitude star near the place 
given by Tycho as that occupied by the stranger. Many 
other faint stars are scattered about, however, and Ty- 
cho's measures were not sufficiently exact to enable us to 
identify the precise position of his star. If the phenome- 
non was due to a collision, no reappearance of the star is 
to be expected. 

Camelopardalus is a very inconspicuous constellation, 
yet it furnishes considerable occupation for the telescope. 
S 390, of magnitude five, has a companion of magnitude 
nine and a half, distance 15", 160. 2 385, also of the fifth 
magnitude, has a ninth-magnitude companion, distance 
only 2.4", p. 160. According to some observers, the 
larger star is yellow and the smaller white. The star 1 is 
a very pretty double, magnitudes both six, distance 10.4". 
Its neighbor 2 of magnitude six has an eighth-magnitude 



PISCES, ARIES, TAURUS, AND THE NORTHERN STARS 135 

companion, distance 1.7", p. 278. The star 7 of mag- 
nitude five is also double, the companion of magnitude 
eight being distant only 1.2". A glance at star cluster 
940, which shows a slight central condensation, completes 
our work in Camelopardalus, and we turn to Ursa Major, 
represented in map No. 26. Here there are many interest- 
ing doubles and triples. Beginning with i we find at once 
occupation for our largest glass. The magnitudes are 
three and ten, distance 10", p. 357. In the double star 23 
the magnitudes are four and nine, distance 23", p. 272. 
A more pleasing object is o- 2 , a greenish fifth-magnitude 
star which has an eighth-magnitude companion, distance 
2.6", p. 245. A good double for our four-inch glass is f, 
whose magnitudes are four and five, distance 1.87", p. 
183. This is a binary with a period of revolution of 
about sixty years, and is interesting as the first binary 
star whose orbit was determined. Savary calculated it in 
1828. Near by is */, a difficult double, magnitudes four 
and ten and a half, distance 7", p. 147. In 57 we find 
again an easy double magnitudes six and eight, distance 
5.5", p. 4. Another similar double is 65, magnitudes six 
and eight, distance 3.9", p. 38. A third star, magnitude 
seven, is seen at a distance of 114" from the primary. 

We come now to Ursa Major's principal attraction f, 
frequently called Mizar. The naked eye perceives near it 
a smaller star, named Alcor. With the three-inch glass 
and a medium power we divide Mizar into two bright stars 
brilliantly contrasted in color, the larger being white and 
the smaller blue-green. Beside Alcor, several fainter stars 
are seen scattered over the field of view, and, taken all 
in all, there are very few equally beautiful sights in the 
starry heavens. The magnitudes of the double are three 
and four, distance 14.5", p. 148. The large star is again 
double, although no telescope has been able to show it so, 



136 PLEASURES OF THE TELESCOPE 

its duplicity being revealed, like that of /? AurigaB, by the 
periodical splitting of the lines in its spectrum. 

Ursa Major contains several nebulae which may be 
glimpsed with telescopes of moderate dimensions. An in- 
teresting pair of these objects, both of which are included 
in one field of view, is formed by 1949 and 1950. The first 
named is the brighter of the two, its nucleus resembling a 
faint star. The nebula 2343 presents itself to us in the 
form of a faint, hazy star, but with large telescopes its 
appearance is very singular. According to a picture 
made by Lord Rosse, it bears no little resemblance to a 
skull, there being two symmetrically placed holes in it, 
each of which contains a star. 

The portion of Canes Venatici, represented in map No. 
26, contains two or three remarkable objects. 2 1606 is a 
close double, magnitudes six and seven, distance 1", p. 
336. It is a pretty sight with the five-inch. The double 
star 2 is singular in that its larger component is red and 
its smaller blue; magnitudes six and eight, distance 
11.4", p. 260. Still more beautiful is 12, commonly called 
Cor Caroli. This double is wide, and requires but a slight 
magnifying power. The magnitudes are three and six, 
distance 20", colors white or light yellow and blue. The 
nebula 3572, although we can see it only as a pair of misty 
specks, is in reality a very wonderful object. Lord Rosse's 
telescope has revealed in it a complicated spiral struc- 
ture, recalling the photographs of the Andromeda nebula, 
and indicating that stupendous changes must be in pro- 
cess within it, although our records of observation are 
necessarily too brief to bring out any perceptible altera- 
tion of figure. It would seem that the astronomer has, of 
all men, the best reasons for complaining of the brevity 
of human life. 

Lastly, we turn to Ursa Minor and the Pole Star. The 



URSA MINOR 



CAMELOPARDALUS 



:ANES VENATICI 



URSA MAJOR 



LEO MINOR 



MAP No. 26. 



10 



138 PLEASURES OF THE TELESCOPE 

latter is a celebrated double, not difficult, except with a 
telescope of less than three inches aperture in the hands 
of an inexperienced observer. The magnitudes are two 
and nine, distance 18.5". The small star has a dull blue 
color. In 1899 it was discovered by spectroscopic evi- 
dence that the Pole Star is triple. In IT' we see a wide 
double, magnitudes six and seven, distance 30", p. 83. 
This completes our survey of the starry heavens. 



CHAPTEK VIII 

SCENES ON THE PLANETS 

"These starry globes far surpassed the earth in grandeur, and the latter 
looked so diminutive that our empire, which appeared only as a point on its sur- 
face, awoke my pity." CICERO, THE DREAM OF SCIPIO. 

ALTHOUGH amateurs have played a conspicuous part 
in telescopic discovery among the heavenly bodies, yet 
every owner of a small telescope should not expect to at- 
tach his name to a star. But he certainly can do some- 
thing perhaps more useful to himself and his friends; he 
can follow the discoveries that others, with better appli- 
ances and opportunities, have made, and can thus impart 
to those discoveries that sense of reality which only comes 
from seeing things with one's own eyes. There are hun- 
dreds of things continually referred to in books and writ- 
ings on astronomy which have but a misty and uncertain 
significance for the mere reader, but which he can easily 
verify for himself with the aid of a telescope of four or 
five inches aperture, and which, when actually confronted 
by the senses, assume a meaning, a beauty, and an im- 
portance that would otherwise entirely have escaped him. 
Henceforth every allusion to the objects he has seen is 
eloquent with intelligence and suggestion. 

Take, for instance, the planets that have been the sub- 
ject of so many observations and speculations of late 
years Mars, Jupiter, Saturn, Venus. For the ordinary 
reader much that is said about them makes very little im- 

139 



140 PLEASURES OF THE TELESCOPE 

pression upon his mind, and is almost unintelligible. He 
reads of the " snow patches " on Mars, but unless he has 
actually seen the whitened poles ,Df that planet he can 
form no clear image in his mind of what is meant. So the 
" belts of Jupiter " is a confusing and misleading phrase 
for almost everybody except the astronomer, and the 
rings of Saturn are beyond comprehension unless they 
have actually been seen. 

It is true that pictures and photographs partially sup- 
ply the place of observation, but by no means so success- 
fully as many imagine. The most realistic drawings and 
the sharpest photographs in astronomy are those of the 
moon, yet I think nobody would maintain that any picture 
in existence is capable of imparting a really satisfactory 
visual impression of the appearance of the lunar globe. 
Nobody who has not seen the moon with a telescope it 
need not be a large one can form a correct and definite 
idea of what the moon is like. 

The satisfaction of viewing with one's own eyes some 
of the things the astronomers write and talk about is very 
great, and the illumination that comes from such viewing 
is equally great. Just as in foreign travel the actual see- 
ing of a famous city, a great gallery filled with master- 
pieces, or a battlefield where decisive issues have been 
fought out illuminates, for the traveler's mind, the events 
of history, the criticisms of artists, and the occurrences of 
contemporary life in foreign lands, so an acquaintance 
with the sights of the heavens gives a grasp on astronom- 
ical problems that can not be acquired in any other way. 
The person who has been in Rome, though he may be no 
archaeologist, gets a far more vivid conception of a new 
discovery in the Forum than does the reader who has 
never seen the city of the Seven Hills; and the amateur 
who has looked at Jupiter with a telescope, though he 



SCENES ON THE PLANETS 



141 



may be no astronomer, finds that the announcement of 
some change among the wonderful belts of that cloudy 
planet has for him a meaning and an interest in which the 
ordinary reader can not share. 

Jupiter is perhaps the easiest of all the planets for the 
amateur observer. A three-inch telescope gives beauti- 
ful views of the great 
planet, although a four- 
inch or a five-inch is 
of course better. But 
there is no necessity 
for going beyond six 
inches' aperture in any 
case. For myself, I 
should care for nothing 
better than my Byrne 
five-inch of fifty - two 
inches' focal distance. 
With such a glass 
more details are visi- 
ble in the dark belts 

and along the bright equatorial girdle than can be correct- 
ly represented in a sketch before the rotation of the planet 
has altered their aspect, while the shadows of the satel- 
lites thrown upon the broad disk, and the satellites them- 
selves when in transit, can be seen sometimes with ex- 
quisite clearness. The contrasting colors of various parts 
of the disk are also easily studied with a glass of four or 
five inches' aperture. 

There is a charm about the great planet when he rides 
high in a clear evening sky, lording it over the fixed stars 
with his serene, unflickering luminousness, which no pos- 
sessor of a telescope can resist. You turn the glass upon 
him and he floats into the field of view, with his cortege of 




JUPITER SEEN WITH A FIVE-INCH TELESCOPE. 
Shadow of a satellite visible. 



142 PLEASURES OF THE TELESCOPE 

satellites, like a yellow-and-red moon, attended by four 
miniatures of itself. You instantly comprehend Jupiter's 
mastery over his satellites their allegiance is evident. 
No one would for an instant mistake them for stars acci- 
dentally seen in the same field of view. Although it re- 
quires a very large telescope to magnify their disks to 
measurable dimensions, yet the smallest glass differen- 
tiates them at once from the fixed stars. There is some- 
thing almost startling in their appearance of companion- 
ship with the huge planet this sudden verification to your 
eyes of the laws of gravitation and of central forces. It 
is easy, while looking at Jupiter amid his family, to under- 
stand the consternation of the churchmen when Galileo's 
telescope revealed that miniature of the solar system, and 
it is gratifying to gaze upon one of the first battle grounds 
whereon science gained a decisive victory for truth. 

The swift changing of place among the satellites, as 
well as the rapidity of Jupiter's axial rotation, give the 
attraction of visible movement to the Jovian spectacle. 
The planet rotates in four or five minutes less than ten 
hours in other words, it makes two turns and four tenths 
of a third turn while the earth is rolling once upon its 
axis. A point on Jupiter's equator moves about twenty- 
seven thousand miles, or considerably more than the en- 
tire circumference of the earth, in a single hour. The 
effect of this motion is clearly perceptible to the observer 
with a telescope on account of the diversified markings 
and colors of the moving disk, and to watch it is one of 
the greatest pleasures that the telescope affords. 

It would be possible, when the planet is favorably situ- 
ated, to witness an entire rotation of Jupiter in the course 
of one night, but the beginning and end of the observation 
would be more or less interfered with by the effects of 
low altitude, to say nothing of the tedium of so long a 



SCENES ON THE PLANETS 143 

vigil. But by looking at the planet for an hour at a time 
in the course of a few nights every side of it will have 
been presented to view. Suppose the first observation is 
made between nine and ten o'clock on any night which 
may have been selected. Then on the following night be- 
tween ten and eleven o'clock Jupiter will have made two 
and a half turns upon his axis, and the side diametrically 
opposite to that seen on the first night will be visible. On 
the third night between eleven and twelve o'clock Jupiter 
will have performed five complete rotations, and the side 
originally viewed will be visible again. 

Owing to the rotundity of the planet, only the central 
part of the disk is sharply defined, and markings which 
can be easily seen when centrally located become indis- 
tinct or disappear altogether when near the limb. Ap- 
proach to the edge of the disk also causes a foreshorten- 
ing which sometimes entirely alters the aspect of a mark- 
ing. It is advisable, therefore, to confine the attention 
mainly to -the middle of the disk. As time passes, clearly 
defined markings on or between the cloudy belts will be 
seen to approach the western edge of the disk, gradually 
losing their distinctness and altering their appearance, 
while from the region of indistinct definition near the 
eastern edge other markings slowly emerge and advance 
toward the center, becoming sharper in outline and more 
clearly defined in color as they swing into view. 

Watching these changes, the observer is carried away 
by the reflection that he actually sees the turning of an- 
other distant world upon its axis of rotation, just as he 
might view the revolving earth from a standpoint on the 
moon. Belts of reddish clouds, many thousands of miles 
across, are stretched along on each side of the equator 
of the great planet he is watching; the equatorial belt 
itself, brilliantly lemon-hued, or sometimes ruddy, is di- 



144 



PLEASURES OF THE TELESCOPE 



versified with white globular and balloon-shaped masses, 
which almost recall the appearance of summer cloud 



I W 




ECLIPSES AND TRANSITS OF JUPITER'S SATELLITES. 
Satellite I and the shadow of III are seen in transit. IV is about to be eclipsed. 

domes hanging over a terrestrial landscape, while toward 
the poles shadowy expanses of gradually deepening blue 



SCENES ON THE PLANETS 145 

or blue-gray suggest the comparative coolness of those 
regions which lie always under a low sun. 

After a few nights' observation even the veriest ama- 
teur finds himself recognizing certain shapes or appear- 
ances a narrow dark belt running slopingly across the 
equator from one of the main cloud zones to the other, 
or a rift in one of the colored bands, or a rotund white 
mass apparently floating above the equator, or a broad 
scallop in the edge of a belt like that near the site of the 
celebrated " red spot," whose changes of color and aspect 
since its first appearance in 1878, together with the light 
it has thrown on the constitution of Jupiter's disk, have 
all but created a new Jovian literature, so thoroughly and 
so frequently have they been discussed. 

And, having noticed these recurring features, the ob- 
server will begin to note their relations to one another, 
and will thus be led to observe that some of them gradu- 
ally drift apart, while others drift nearer; and after a 
time, without any aid from books or hints from observa- 
tories, he will discover for himself that there is a law gov- 
erning the movements on Jupiter's disk. Upon the whole 
he will find that the swiftest motions are near the equator, 
and the slowest near the poles, although, if he is per- 
sistent and has a good eye and a good instrument, he will 
note exceptions to this rule, probably arising, as Pro- 
fessor Hough suggests, from differences of altitude in Jupi- 
ter's atmosphere. Finally, he will conclude that the co- 
lossal globe before him is, exteriorly at least, a vast ball 
of clouds and vapors, subject to tremendous vicissitudes, 
possibly intensely heated, and altogether different in its 
physical constitution, although made up of similar ele- 
ments, from the earth. Then, if he chooses, he can sail off 
into the delightful cloud-land of astronomical speculation, 
and make of the striped and spotted sphere of Jove just 



146 PLEASURES OF THE TELESCOPE 

such a world as may please his fancy for a world of some 
kind it certainly is. 

For many observers the satellites of Jupiter possess 
even greater attractions than the gigantic ball itself. As 
I have already remarked, their movements are very notice- 
able and lend a wonderful animation to the scene. Al- 
though they bear classical names, they are almost univer- 
sally referred to by their Roman numbers, beginning with 
the innermost, whose symbol is I, and running outward in 
regular order II, III, and IV.* The minute satellite much 
nearer to the planet than any of the others, which Mr. 
Barnard discovered with the Lick telescope in 1892, is 
called the fifth, although in the order of distance it would 
be the first. In size and importance, however, it can not 
rank with its comparatively gigantic brothers. Of course, 
no amateur's telescope can afford the faintest glimpse 
of it. 

Satellite I, situated at a mean distance of 261,000 miles 
from Jupiter's center about 22,000 miles farther than the 
moon is from the earth is urged by its master's overpow- 
ering attraction to a speed of 320 miles per minute, so 
that it performs a complete revolution in about forty-two 
hours and a half. The others, of course, move more 
slowly, but even the most distant performs its revolution 
in several hours less than sixteen days. The plane of 
their orbits is presented edgewise toward the earth, from 
which it follows that they appear to move back and forth 
nearly in straight lines, some apparently approaching the 
planet, while others are receding from it. The changes in 
their relative positions, which can be detected from hour 
to hour, are very striking night after night, and lead to a 
great variety of arrangements always pleasing to the eye. 

* Their names, in the same order as their numbers, are lo, Europa, Gany- 
mede, and Callisto. 



SCENES ON THE PLANETS 147 

The most interesting phenomena that they present 
are their transits and those of their round, black shadows 
across the face of the planet; their eclipses by the 
planet's shadow, when they disappear and afterward re- 
appear with astonishing suddenness; and their occulta- 
tions by the globe of Jupiter. Upon the whole, the most 
interesting thing for the amateur to watch is the passage 
of the shadows across Jupiter. The distinctness with 
which they can be seen when the air is steady is likely to 
surprise, as it is certain to delight, the observer. When 
it falls upon a light part of the disk the shadow of a satel- 
lite is as black and sharply outlined as a drop of ink; on a 
dark-colored belt it can not so easily be seen. 

It is more difficult to see the satellites themselves in 
transit. There appears to be some difference among 
them as to visibility in such circumstances. Owing to 
their luminosity they are best seen when they have a dark 
belt for a background, and are least easily visible when 
they appear against a bright portion of the planet. Every 
observer should provide himself with a copy of the Ameri- 
can Ephemeris for the current year, wherein he will find 
all the information needed to enable him to identify the 
various satellites and to predict, by turning Washington 
mean time into his own local time, the various phenomena 
of the transits and eclipses. 

While a faithful study of the phenomena of Jupiter is 
likely to lead the student to the conclusion that the great- 
est planet in our system is not a suitable abode for life, 
yet the problem of its future, always fascinating to the 
imagination, is open; and whosoever may be disposed to 
record his observations in a systematic manner may at 
least hope to render aid in the solution of that problem. 

Saturn ranks next to Jupiter in attractiveness for the 
observer with a telescope. The rings are almost as mysti- 




PLEASURES OF THE TELESCOPE 

fying to-day as they were in the time of Herschel. There 
is probably no single telescopic view that can compare in 
the power to excite wonder with that of Saturn when the 
ring system is not so widely opened" but that both poles of 
the planet project beyond it. One returns to it again and 

again with unflagging interest, 
and the beauty of the spec- 
tacle quite matches its singu- 
larity. When Saturn is in 
view the owner of a telescope 
may become a recruiting offi- 
<*r for astronomy by simply 
inviting his friends to gaze 

at the wonderful planet. The silvery color of the ball, 
delicately chased with half-visible shadings, merging one 
into another from the bright equatorial band to the bluish 
polar caps; the grand arch of the rings, sweeping across 
the planet with a perceptible edging of shadow; their 
sudden disappearance close to the margin of the ball, 
where they go behind it and fall straightway into night; 
the manifest contrast of brightness, if not of color, be- 
tween the two principal rings; the fine curve of the black 
line marking the 1,600-mile gap between their edges 
these are some of the elements of a picture that can never 
fade from the memory of any one who has once beheld it 
in its full glory. 

Saturn's moons are by no means so interesting to 
watch as are those of Jupiter. Even the effect of their 
surprising number (raised to nine by Professor Pickering's 
discovery in 1899 of a new one which is almost at the limit 
of visibility, and was found only with the aid of pho- 
tography) is lost, because most of them are too faint to 
be seen with ordinary telescopes, or, if seen, to make any 
notable impression upon the eye. The two largest Titan 



SCENES ON THE PLANETS 149 

and Japetus are easily found, and Titan is conspicuous, 
but they give none of that sense of companionship and 
obedience to a central authority which strikes even the 
careless observer of Jupiter's system. This is owing 




POLAR VIEW OF SATURN'S SYSTEM. 

The orbits of the five nearest satellites are shown. The dotted line outside the rings 
shows Roche's limit. 

partly to their more deliberate movements and partly to 
the inclination of the plane of their orbits, which seldom 
lies edgewise toward the earth. 

But the charm of the peerless rings is abiding, and the 
interest of the spectator is heightened by recalling what 



150 PLEASURES OF THE TELESCOPE 

science has recently established as to their composition. 
It is marvelous to think, while looking upon their broad, 
level surfaces as smooth, apparently, as polished steel, 
though thirty thousand miles across that they are in 
reality vast circling currents of meteoritic particles or 
dust, through which run immense waves, condensation 
and rarefaction succeeding one another as in the undula- 
tions of sound. Yet, with all their inferential tumult, 
they may actually be as soundless as the depths of inter- 
stellar space, for Struve has shown that those spectacu- 
lar rings possess no appreciable mass, and, viewed from 
Saturn itself, their (to us) gorgeous seeming bow may 
appear only as a wreath of shimmering vapor spanning 
the sky and paled by the rivalry of the brighter stars. 

In view of the theory of tidal action disrupting a satel- 
lite within a critical distance from the center of its pri- 
mary, the thoughtful observer of Saturn will find himself 
wondering what may have been the origin of the rings. 
The critical distance referred to, and which is known as 
Roche's limit, lies, according to the most trustworthy esti- 
mates, just outside the outermost edge of the rings. It 
follows that if the matter composing the rings were col- 
lected into a single body that body would inevitably be 
torn to pieces and scattered into rings; and so, too, if in- 
stead of one there were several or many bodies of consid- 
erable size occupying the place of the rings, all of these 
bodies would be disrupted and scattered. If one of the 
present moons of Saturn for instance, Mimas, the inner- 
most hitherto discovered should wander within the 
magic circle of Roche's limit it would suffer a similar fate, 
and its particles would be disseminated among the rings. 
One can hardly help wondering whether the rings have 
originated from the demolition of satellites Saturn de- 
vouring his children, as the ancient myths represent, and 



SCENES ON THE PLANETS 151 

encircling himself, amid the fury of destruction, with the 
dust of his disintegrated victims. At any rate, the ama- 
teur student of Saturn will find in the revelations of his 
telescope the inspirations of poetry as well as those of 
science, and the bent of his mind will determine which he 
shall follow. 

Professor Pickering's discovery of a ninth satellite of 
Saturn, situated at the great distance of nearly eight mil- 
lion miles from the planet, serves to call attention to the 
vastness of the " sphere of activity " over which the 
ringed planet reigns. Surprising as the distance of the 
new satellite appears when compared with that of our 
moon, it is yet far from the limit where Saturn's control 
ceases and that of the sun becomes predominant. That 
limit, according to Prof. Asaph HalPs calculation, is 
nearly 30,000,000 miles from Saturn's center, while if our 
moon were removed to a distance a little exceeding 
500,000 miles the earth would be in danger of losing its 
satellite through the elopement of Artemis with Apollo. 

Although, as already remarked, the satellites of Sat- 
urn are not especially interesting to the amateur tele- 
scopist, yet it may be well to mention that, in addition to 
Titan and Japetus, the satellite named Khea, the fifth in 
order of distance from the planet, is not a difficult object 
for a three- or four-inch telescope, and two others consid- 
erably fainter than Rhea Dione (the fourth) and Tethys 
(the third) may be seen in favorable circumstances. The 
others Mimas (the first), Enceladus (the second), and 
Hyperion (the seventh) are beyond the reach of all but 
large telescopes. The ninth satellite, which has received 
the name of Phoebe, is much fainter than any of the 
others, its stellar magnitude being reckoned by its discov- 
erer at about 15.5. 

Mars, the best advertised of all the planets, is nearly 



J52 



PLEASURES OF THE TELESCOPE 



the least satisfactory to look at except during a favorable 
opposition, like those of 1877 and 1892, when its compara- 
tive nearness to the earth renders some of its character- 
istic features visible in a small telescope. The next favor- 
able opposition will occur in 1907. 

When well seen with an ordinary telescope, say a four- 
or five-inch glass, Mars shows three peculiarities that may 
be called fairly conspicuous viz., its white polar cap, its 
general reddish, or orange-yellow, hue, and its dark mark- 
ings, one of the clearest of which is the so-called Syrtis 
Major, or, as it was once named on account of its shape, 
" Hourglass Sea." Other dark expanses in the southern 
hemisphere are not difficult to be seen, although their out- 
lines are more or less misty and indistinct. The gradual 
diminution of the polar cap, which certainly behaves in this 
respect as a mass of snow and ice would do, is a most in- 
teresting spectacle. As 
summer advances in the 
southern hemisphere of 
Mars, the white circular 
patch surrounding the 
pole becomes smaller, 
night after night, until 
it sometimes disappears 
entirely even from the 
ken of the largest tele- 
scopes. At the same 
time the dark expanses 
become more distinct, as 
if the melting of the 

polar snows had supplied them with a greater depth of 
water, or the advance of the season had darkened them 
with a heavier growth of vegetation. 

The phenomena mentioned above are about all that a 




MARS SEEN WITH A FIVE-INCH TELESCOPE. 



SCENES ON THE PLANETS 



153 



small telescope will reveal. Occasionally a dark streak, 
which large instruments show is connected with the mys- 
terious system of " canals," can be detected, but the " ca- 
nals " themselves are far beyond the reach of any tele- 
scope except a few of the giants handled by experienced 
observers. The conviction which seems to have forced its 
way into the minds even of some conservative astrono- 
mers, that on Mars the conditions, to use the expression 
of Professor Young, " are more nearly earthlike than on 
any other of the heavenly bodies which we can see with 
our present telescopes," is sufficient to make the planet a 
center of undying inter- 
est notwithstanding the 
difficulties with which 
the amateur is confront- 
ed in his endeavors to 
see the details of its 
markings. 

In Venus " the fatal 
gift of beauty " may be 
said, as far as our obser- 
vations are concerned, 
to be matched by the 
equally fatal gift of 
brilliance. Whether it 
be due to atmospheric 
reflection alone or to 

the prevalence of clouds, Venus is so bright that consid- 
erable doubt exists as to the actual visibility of any per- 
manent markings on her surface. The detailed representa- 
tions of the disk of Venus by Mr. Percival Lowell, showing 
in some respects a resemblance to the stripings of Mars, 
can not yet be accepted as decisive. More experienced 

astronomers than Mr. Lowell have been unable to see at 
11 




THE ILLUMINATION OP VENUS'S ATMOSPHERE AT THE 

BEGINNING OF HER TRANSIT ACROSS THE SUN. 



154 PLEASURES OF THE TELESCOPE 

all things which he draws with a fearless and unhesitating 
pencil. That there are some shadowy features of the 
planet's surface to be seen in favourable circumstances is 
probable, but the time for drawing'a " map of Venus " has 
not yet come. 

The previous work of Schiaparelli lends a certain de- 
gree of probability to Mr. Lowell's observations on the 
rotation of Venus. This rotation, according to the origi- 
nal announcement of Schiaparelli, is probably performed 
in the same period as the revolution around the sun. In 
other words, Venus, if Schiaparelli and Lowell are right, 
always presents the same side to the sun, possessing, in 
consequence, a day hemisphere and a night hemisphere 
which never interchange places. This condition is so an- 
tagonistic to all our ideas of what constitutes habitability 
for a planet that one hesitates to accept it as proved, and 
almost hopes that it may turn out to have no real exist- 
ence. Venus, as the twin of the earth in size, is a planet 
which the imagination, warmed by its sunny aspect, would 
fain people with intelligent beings a little fairer than our- 
selves; but how can such ideas be reconciled with the pic- 
ture of a world one half of which is subjected to the merci- 
less rays of a never-setting sun, while the other half is 
buried in the fearful gloom and icy chill of unending 
night? 

Any amateur observer who wishes to test his eyesight 
and his telescope in the search of shades or markings on 
the disk of Venus by the aid of which the question of its 
rotation may finally be settled should do his work while 
the sun is still above the horizon. Schiaparelli adopted 
that plan years ago, and others have followed him with 
advantage. The diffused light of day serves to take off 
the glare which is so serious an obstacle to the successful 
observation of Venus when seen against a dark sky. 



SCENES ON THE PLANETS 155 

Knowing the location of Venus in the sky, which can be 
ascertained from the Ephemeris, the observer can find it 
by day. If his telescope is not permanently mounted and 
provided with " circles " this may not prove an easy thing 
to do, yet a little perseverance and ingenuity will effect it. 
One way is to find, with a star chart, some star whose 
declination is the same, or verv nearly the same, as that of 
Venus, and which crosses the meridian say twelve hours 
ahead of her. Then set the telescope upon that star, 
when it is on the meridian at night, and leave it there, and 
the next day, twelve hours after the star crossed the me- 
ridian, look into your telescope and you will see Venus, or, 
if not, a slight motion of the tube will bring her into view. 

For many amateurs the phases of Venus will alone 
supply sufficient interest for telescopic observation. The 
changes in her form, from that of a round full moon when 
she is near superior conjunction to the gibbous, and finally 
the half-moon phase as she approaches her eastern elonga- 
tion, followed by the gradually narrowing and lengthen- 
ing crescent, until she is a mere silver sickle between the 
sun and the earth, form a succession of delightful pictures. 

Not very much can be said for Mercury as a telescopic 
object. The little planet presents phases like those of 
Venus, and, according to Schiaparelli and Lowell, it re- 
sembles Venus in its rotation, keeping always the same 
side to the sun. In fact, Schiaparelli's discovery of this 
peculiarity in the case of Mercury preceded the similar 
discovery in the case of Venus. There are markings on 
Mercury which have reminded some astronomers of the 
moon, and there are reasons for thinking that the planet 
can not be a suitable abode for living beings, at least for 
beings resembling the inhabitants of the earth. 

Uranus and Neptune are too far away to present any 
attraction for amateur observers. 



CHAPTER IX 

THE MOUNTAINS AND PLAINS OF THE MOON, AND THE 
SPECTACLES OF THE SUN 

"... the Moon, whose orb 
The Tuscan artist views through optic glass 
At evening from the top of Fesole, 
Or in Valdarno, to descry new lands, 
Rivers or mountains in her spotty globe. " PARADISE LOST. 

THE moon is probably the most interesting of all tele- 
scopic objects. This arises from its comparative near- 
ness to the earth. A telescope magnifying 1,000 diam- 
eters brings the moon within an apparent distance of 
less than 240 miles. If telescopes are ever made with 
a magnifying power of 10,000 diameters, then, provided 
that atmospheric difficulties can be overcome, we shall 
see the moon as if it were only about twenty miles off, and 
a sensitive astronomer might be imagined to feel a little 
hesitation about gazing so closely at the moon as if he 
were peering into a neighbor world's window. 

But a great telescope and a high magnifying power are 
not required to interest the amateur astronomer in the 
study, of the moon. Our three-inch telescope is amply 
sufficient to furnish us with entertainment for many an 
evening while the moon is running through its phases, 
and we shall find delight in frequently changing the mag- 
nifying power as we watch the lunar landscapes, because 
every change will present them in a different aspect. 

It should be remembered that a telescope, unless a ter- 
restrial eyepiece or prism is employed, reverses such an 

156 



THE MOUNTAINS AND PLAINS OF THE MOON 157 

object as the moon top for bottom. Accordingly, if the 
moon is on or near the meridian when the observations 
are made, we shall see the north polar region at the 
bottom and the south polar region at the top. In other 
words, the face of the moon as presented in the telescope 
will be upside down, north and south interchanging places 
as compared with their positions in a geographical map. 
But east and west remain unaltered in position, as com- 
pared with such a map i. e., the eastern hemisphere of 
the moon is seen on the right and the western hemisphere 
on the left. It is the moon's western edge that catches 
the first sunlight when " new moon " begins, and, as the 
phase increases, passing into " first quarter " and from 
that to " full moon," the illumination sweeps across the 
disk from west to east. 

The narrow sickle of the new moon, hanging above the 
sunset, is a charming telescopic sight. Use a low power, 
and observe the contrast between the bright, smooth 
round of the sunward edge, which has almost the polish 
of a golden rim, and the irregular and delicately shaded 
inner curve, where the adjacent mountains and plains 
picturesquely reflect or subdue the sunshine. While the 
crescent grows broader new objects are continually com- 
ing into view as the sun rises upon them, until at length 
one of the most conspicuous and remarkable of the lunar 
" seas," the Mare Crisium, or Sea of Crises, lies fully dis- 
played amid its encircling peaks, precipices, and craters. 
The Mare Crisium is all in the sunlight between the third 
and fourth day after " new moon." It is about 350 by 280 
miles in extent, and if ever filled with water must have 
been a very deep sea, since its arid bed lies at a great but 
not precisely ascertained depth below the general level 
of the moon. There are a few small craters on the floor of 
the Mare Crisium^ the largest bearing the name of Picard, 



158 



PLEASURES OF THE TELESCOPE 



and its borders are rugged with mountains. On the 
southwestern side is a lofty promontory, 11,000 feet in 
height, called Cape Agarum. At the middle of the east- 
ern side a kind of bay opens deep in the mountains, whose 



& ILssV 
Fir micas } *> \ 

U J^Av 



8 >& '@ 

^Taruntius MARE 

TRANQUILITATIS 






^ MARE 

'luut Caesar 
^ VAPOKUM 




LUNAR CHART No. 1, NORTHWEST QUARTER. 



range here becomes very narrow. Southeast of this bay 
lies a conspicuous bright point, the crater mountain Pro- 
clus, on which the sun has fully risen in the fourth day of 
the moon, and which reflects the light with extraordinary 
liveliness. Adjoining Proclus on the east and south is a 



THE MOUNTAINS AND PLAINS OF THE MOON 159 

curious, lozenge-shaped flat, broken with short, low ridges, 
and possessing a most peculiar light-brown tint, easily dis- 
tinguished from the general color tone of the lunar land- 
scapes. It would be interesting to know what was passing 
in the mind of the old astronomer who named this singular 

O 

region Palus Somnii. It is not the only spot on the moon 
which has been called a " marsh," and to which an unex- 
plained connection with dreams has been ascribed. 

Nearly on the same meridian with Proclus, at a distance 
of about a hundred miles northward, lies a fine example of 
a ring mountain, rather more than forty miles in diameter, 
and with peak-tipped walls which in some places are 
13,000 feet in height, as measured from the floor within. 
This is Macrobius. There is an inconspicuous central 
mountain in the ring. 

North of the Mare Crisium, and northwest of Macro- 
bius, we find a much larger mountain ring, oblong in 
shape and nearly eighty miles in its greatest diameter. 
It is named Cleomenes. The highest point on its wall is 
about 10,000 feet above the interior. Near the northeast 
corner of the wall yawns a huge and very deep crater, 
Tralles, while at the northern end is another oblong 
crater mountain called Burckhardt. 

From Cleomenes northward to the pole, or to the 
northern extremity of the crescent, if our observations 
are made during new moon, the ground appears broken 
with an immense number of ridges, craters, and mountain 
rings, among which we may telescopically wander at will. 
One of the more remarkable of these objects, which may 
be identified with the aid of Lunar Chart No. 1, is the vast 
ringed plain near the edge of the disk, named Gauss. It 
is more than a hundred and ten miles in diameter. Owing 
to its situation, so far down the side of the lunar globe, it 
is foreshortened into a long ellipse, although in reality it 



160 PLEASURES OF THE TELESCOPE 

is nearly a circle. A chain of mountains runs north and 
south across the interior plain. Geminus, Berzelius, and 
Messala are other rings well worth looking at. The re- 
markable pair called Atlas and Hercules demand more 
than passing attention. The former is fifty-five and the lat- 
ter forty-six miles in diameter. Each sinks 11,000 feet be- 
low the summit of the loftiest peak on its encircling wall. 
Both are full of interesting detail sufficient to occupy the 
careful observer for many nights. The broad ring bearing 
the name of Endymion is nearly eighty miles in diameter, 
and has one peak 15,000 feet high. The interior plain is flat 
and dark. Beyond Endymion on the edge of the disk is 
part of a gloomy plain called the Mare Humboltianum. 

After glancing at the crater-shaped mountains on the 
western and southern border of the Mare Crisium, Alha- 
zen, Hansen, Condorcet, Firmicus, etc., we pass southward 
into the area covered in Lunar Chart No. 2. The long 
dark plain south of the Mare Crisium is the Mare Fecundi- 
tatiSy though why it should have been supposed to be par- 
ticularly fecund, or fertile, is by no means clear. On the 
western border of this plain, about three hundred miles 
from the southern end of the Mare Crisium, is the mountain 
ring, or circumvallation, called Langrenus, about ninety 
miles across and in places 10,000 feet high. There is a fine 
central mountain with a number of peaks. Nearly a hun- 
dred miles farther south, on the same meridian, lies an 
equally extensive mountain ring named Vendelinus. The 
broken and complicated appearance of its northern walls 
will command the observer's attention. Another similar 
step southward, and still on the same meridian brings us to 
a yet finer mountain ring, slightly larger than the others, 
and still more complicated in its walls, peaks, and terraces, 
and in its surroundings of craters, gorges, and broken 
ridges. This is Petavius. West of Petavius, on the very 



THE MOUNTAINS AND PLAINS OF THE MOON 



161 



edge of the disk, is a wonderful formation, a walled plain 
named Humboldt, which is looked down upon at one point 
near its eastern edge by a peak 16,000 feet in height. 
About a hundred and forty miles south of Petavius is the 



4&* 




LUNAK CHART No. 2, SOUTHWEST QUARTER. 

fourth great mountain ring lying on the same meridian. 
Its name is Furnerius. Look particularly at the brilliantly 
shining crater on the northeast slope of the outer wall of 
Furnerius. 



162 PLEASURES OF THE TELESCOPE 

Suppose that our observations are now interrupted, 
to be resumed when the moon, about " seven days old," is 
in its first quarter. If we had time, it would be a most 
interesting thing to watch the advance of the lunar sun- 
rise every night, for new beauties are displayed almost 
from hour to hour; but, for the purposes of our descrip- 
tion, it is necessary to curtail the observations. At first 
quarter one half of the lunar hemisphere which faces the 
earth is illuminated by the sun, and the line of sunrise 
runs across some of the most wonderful regions of the 
moon. 

We begin, referring once more to Lunar Chart No. 1, 
in the neighborhood of the north pole of the moon. Here 
the line along which day and night meet is twisted and 
broken, owing to the roughness of the lunar surface. 
About fifteen degrees southwest of the pole lies a remark- 
able square-cornered, mountain-bordered plain, about 
forty miles in length, called Barrow. Very close to the 
pole is a ring mountain, about twenty-five miles in diam- 
eter, whose two loftiest peaks, 8,000 to 9,000 feet high, 
according to Neison, must, from their situation, enjoy per- 
petual day. 

The long, narrow, dark plain, whose nearest edge is 
about thirty degrees south of the pole, is the Mare Frigoris, 
bordered on both sides by uplands and mountains. At its 
southern edge we find the magnificent Aristoteles, a 
mountain ring, sixty miles across, whose immense wall is 
composed of terraces and ridges running up to lofty peaks, 
which rise nearly 11,000 feet above the floor of the val- 
ley. About a hundred miles south of Aristoteles is Eudox- 
us, another fine mountain ring, forty miles in diameter, 
and quite as deep as its northern neighbor. These two 
make a most striking spectacle. 

We are now in the neighborhood of the greatest moun- 



THE MOUNTAINS AND PLAINS OF TEE MOON 163 

tain chains on the moon, the lunar Alps lying to the 
east and the lunar Caucasus to the south of Aristoteles 
and Eudoxus, while still farther south, separated from the 
Caucasus by a strait not more than a hundred miles 
broad, begins the mighty range of the lunar Apennines. 
We first turn the telescope on the Alps. As the line of 
sunrise runs directly across their highest peaks, the effect 
is startling. The greatest elevations are about 12,000 
feet. The observer's eye is instantly caught by a great 
valley, running like a furrow through the center of the 
mountain mass, and about eighty or ninety miles in 
length. The sealike expanse south and southeast of the 
Alps is the Mare Imbrium, and it is along the coast of this 
so-called sea that the Alps attain their greatest height. 
The valley, or gorge, above mentioned, appears to cut 
through the loftiest mountains and to reach the " coast," 
although it is so narrowed and broken among the greater 
peaks that its southern portion is almost lost before it 
actually reaches the Mare Imbrium. Opening wider again 
as it enters the Mare, it forms a deep bay among precipi- 
tous mountains. 

The Caucasus Mountains are not so lofty nor so pre- 
cipitous as the Alps, and consequently have less attrac- 
tion for the observer. They border the dark, oval plain of 
the Mare Serenitatis on its northeastern side. The great 
bay running out from the Mare toward the northwest, be- 
tween the Caucasus and the huge mountain ring of Posi- 
donius, bears the fanciful name of Lacus Somniorum. In 
the old days when the moon was supposed to be inhabited, 
those terrestrial godfathers, led by the astronomer Ricci- 
oli, who were busy bestowing names upon the " seas " and 
mountains of our patient satellite, may have pleased their 
imagination by picturing this arm of the " Serene Sea " as 
a peculiarly romantic sheet of water, amid whose magni- 



164 PLEASURES OF THE TELESCOPE 

cal influences the lunar gentlefolk, drifting softly in their 
silver galleons and barges, and enjoying the splendors of 
" full earth " poured upon their delightful little world, 
were accustomed to fall into charming reveries, as even 
we hard-headed sons of Adam occasionally do when the 
waters under the keel are calm and smooth and the balmy 
air of a moonlit night invokes the twin spirits of poetry 
and music. 

Posidonius, the dominating feature of the shore line 
here, is an extraordinary example of the many formations 
on the moon which are so different from everything on 
the earth that astronomers do not find it easy to bestow 
upon them names that truly describe them. It may be 
called a ring mountain or a ringed plain, for it is both. 
Its diameter exceeds sixty miles, and the interior plain 
lies about 2,000 feet below the outer surface of the lunar 
ground. The mountain wall surrounding the ring is by 
no means remarkable for elevation, its greatest height 
not exceeding 6,000 feet, but, owing to the broad sweep of 
the curved walls, the brightness of the plain they inclose, 
and the picturesque irregularity of the silhouette of 
shadow thrown upon the valley floor by the peaks encir- 
cling it, the effect produced upon the observer is very 
striking and attractive. 

Having finished with Posidonius and glanced across 
the broken region of the Taurus Mountains toward the 
west, we turn next to consider the Mare Serenitatis. This 
broad gray plain, which, with a slight magnifying power, 
certainly looks enough like a sea to justify the first tele- 
scopists in thinking that it might contain water, is about 
430 by 425 miles in extent, its area being 125,000 square 
miles. Running directly through its middle, nearly in a 
north and south line, is a light streak, which even a good 
opera glass shows. This streak is the largest and most 



THE MOUNTAINS AND PLAINS OF THE MOON 165 

wonderful of the many similar rays which extend on all 
sides from the great crater, or ring, of Tycho in the south- 
ern hemisphere. The ray in question is more than 2,000 
miles long, and, like its shorter congeners, it turns aside 
for nothing; neither " sea," nor peak, nor mountain range, 
nor crater ring, nor gorge, nor caiion, is able to divert it 
from its course. It ascends all heights and drops into 
all depths with perfect indifference, but its continuity is 
not broken. When the sun does not illuminate it at a 
proper angle, however, the mysterious ray vanishes. Is 
it a metallic vein, or is it volcanic lava or ash? Was the 
globe of the moon once split open along this line? 

The Mare Serenitatis is encircled by mountain ranges to 
a greater extent than any of the other lunar " seas." On 
its eastern side the Caucasus and the Apennines shut it in, 
except for a strait a hundred miles broad, by means of 
which it is connected with the Mare Imbrium. On the 
south the range of the Hsemus Mountains borders it, on 
the north and northwest the Caucasus and the Taurus 
Mountains confine it, while on the west, where again it 
connects itself by a narrow strait with another " sea," 
the Mare TranquiUtatis, it encounters the massive uplift 
of Mount Argseus. Not far from the eastern strait is 
found the remarkable little crater named Linne', not con- 
spicuous on the gray floor of the Mare, yet easily enough 
found, and very interesting because a considerable change 
of form seems to have come over this crater some time 
near the middle of the nineteenth century. In referring 
to it as a crater it must not be forgotten that it does 
not form an opening in the top of a mountain. In fact, 
the so-called craters on the moon, generally speaking, are 
simply cavities in the lunar surface, whose bottoms lie 
deep below the general level, instead of being elevated on 
the summit of mountains, and inclosed in a conical peak. 



166 PLEASURES OF THE TELESCOPE 

In regard to the alleged change in Linne, it has been sug- 
gested, not that a volcanic eruption brought it about, but 
that a downfall of steep walls, or of an unsupported rocky 
floor, was the cause. The possibility of such an occur- 
rence, it must be admitted, adds to the interest of the ob- 
server who regularly studies the moon with a telescope. 

Just on the southern border of the Mare, the beautiful 
ring Menelaus lies in the center of the chain of the Hsemus 
Mountains. The ring is about twenty miles across, and 
its central peak is composed of some highly reflecting 
material, so that it shines very bright. The streak or 
ray from Tycho which crosses the Mare Serenitatis passes 
through the walls of Menelaus, and perhaps the central 
peak is composed of the same substance that forms the ray. 
Something more than a hundred miles east-southeast 
from Menelaus, in the midst of the dark Mare Vaporum, is 
another brilliant ring mountain which catches the eye, 
Manilius. It exceeds Menelaus in brightness as well as 
in size, its diameter being about twenty-five miles. There 
is something singular underlying the dark lunar surface 
here, for not only is Manilius extraordinarily brilliant in 
contrast with the surrounding plain, but out of that plain, 
about forty miles toward the east, projects a small moun- 
tain which is also remarkable for its reflecting properties, 
as if the gray ground were underlain by a stratum of some 
material that flashes back the sunlight wherever it is ex- 
posed. The crater mountain, Sulpicius Gallus, on the bor- 
der of the Mare, north of Manilius and east of Menelaus, is 
another example of the strange shining quality of certain 
formations on the moon. 

Follow next the Ha3mus range westward until the at- 
tention falls upon the great ring mountain Plinius, more 
than thirty miles across, and bearing an unusual resem- 
blance to a fortification. Mr. T. G. Elger, the celebrated 



THE MOUNTAINS AND PLAINS OF THE MOON 167 

English selenographer, says of Plinius that, at sunrise, 
" it reminds one of a great fortress or redoubt erected to 
command the passage between the Mare Tranquilitatis and 
the Mare Serenitatis." But, of course, the resemblance is 
purely fanciful. Men, even though they dwelt in the 
moon, would not build a rampart 6,000 feet high! 

Mount Argseus, at the southwest corner of the Mare 
Serenitatis, is a very wonderful object when the sun has 
just risen upon it. This occurs five days after the new 
moon. 

Keturning to the eastern extremity of the Mare, we 
glance, in passing, at the precipitous Mount Hadley, which 
rises more than 15,000 feet above the level of the Mare and 
forms the northern point of the Apennine range. Passing 
into the region of the Mare Imbrium, whose western end is 
divided into the Palus Putredinis on the south and the 
Palus Nebularum on the north, we notice three conspicu- 
ous ring mountains, Cassini near the Alps, and Aristillus 
and Autolycus, a beautiful pair, nearly opposite the 
strait connecting the two Maria. Cassini is thirty-six 
miles in diameter, Aristillus thirty-four, and Autolycus 
twenty-three. The first named is shallow, only 4,000 feet 
in depth from the highest point of its wall, while Aristil- 
lus carries some peaks on its girdle 11,000 feet high. Au- 
tolycus, like Cassini, is of no very great depth. 

Westward from the middle of an imaginary line joining 
Aristillus and Cassini is the much smaller crater Thesete- 
tus. Outside the walls of this are a number of craterlets, 
and a French astronomer, Charbonneaux, of the Meudon 
Observatory, reported in December, 1900, that he had re- 
peatedly observed white clouds appearing and disappear- 
ing over one of these small craters. 

South of the Mare Vaporum are found some of the most 
notable of those strange lunar features that are called 



168 PLEASURES OF THE TELESCOPE 

"clefts " or " rills." Two crater mountains, in particular, 
are connected with them, Ariadseus at the eastern edge of 
the Mare Tranquilitatis and Hyginus on the southern bor- 
der of the Mare Vaporum. These clefts appear to be broad 
and deep chasms, like the caiions cut by terrestrial rivers, 
but it can not be believed that the lunar canons are the 
work of rivers. They are rather cracks in the lunar crust, 
although their bottoms are frequently visible. The prin- 
cipal cleft from Ariadseus runs eastward and passes be- 
tween two neighboring craters, the southern of which is 
named Silberschlag, and is noteworthy for its brightness. 
The Hyginus cleft is broader and runs directly through 
the crater ring of that name. 

The observer will find much to interest him in the 
great, irregular, and much-broken mountain ring called 
Julius Caesar, as well as in the ring mountains, Godin, 
Agrippa, and Triesnecker. The last named, besides pre- 
senting magnificent shadows when the sunlight falls 
aslant upon it, is the center of a complicated system of 
rills, some of which can be traced with our five-inch glass. 

We next take up Lunar Chart No. 2, and pay a tele- 
scopic visit to the southwestern quarter of the lunar 
world. The Mare Tranquilitatis merges through straits 
into two southern extensions, the More Fecunditatis and 
the Mare Ncctaris. The great ring mountains or ringed 
plains, Langrenus, Vendelinus, Petavius, and Furnerius, 
all lying significantly along the same lunar meridian, have 
already been noticed. Their linear arrangement and iso- 
lated position recall the row of huge volcanic peaks that 
runs parallel with the shore of the Pacific Ocean in Oregon 
and Washington Mount Jefferson, Mount Hood, Mount 
St. Helen's, Mount Tacoma but these terrestrial volca- 
noes, except in elevation, are mere pins' heads in the com- 
parison. 



THE MOUNTAINS AND PLAINS OF THE MOON 169 

In the eastern part of the Mare Fecunditatis lies a pair 
of relatively small craters named Messier, which possess 
particular interest because it has been suspected, though 
not proved, that a change of form has occurred in one or 
other of the pair. Madler, in the first half of the nine- 
teenth century, represented the two craters as exactly 
alike in all respects. In 1855 Webb discovered that they 
are not alike in shape, and that the easternmost one is the 
larger, and every observer easily sees that Webb's descrip- 
tion is correct. Messier is also remarkable for the light 
streak, often said to resemble a comet's tail, which ex- 
tends from the larger crater eastward to the shore of the 
Mare Fecunditatis. 

Goclenius and Guttemberg, on the highland between 
the Mare Fecunditatis and the Mare Nectaris, are intersected 
and surrounded by clefts, besides being remarkable for 
their broken and irregular though lofty walls. Guttem- 
berg is forty-five miles and Goclenius twenty-eight miles 
in diameter. The short mountain range just east of Gut- 
temberg, and bordering a part of the Mare Nectaris on the 
west, is called the Pyrenees. 

The Mare Nectaris, though offering in its appearance no 
explanation of its toothsome name perhaps it was re- 
garded as the drinking cup of the Olympian gods is one 
of the most singular of the dark lunar plains in its out- 
lines. At the south it ends in a vast semicircular bay, 
sixty miles across, which is evidently a half-submerged 
mountain ring. But submerged by what? Not water, 
but perhaps a sea of lava which has now solidified and 
forms the floor of the M are Nectaris. The name of this sin- 
gular formation is Fracastorius. Elger has an interest- 
ing remark about it. 

" On the higher portion of the interior, near the cen- 
ter," he says, " is a curious object consisting apparently of 
13 



170 PLEASURES OF THE TELESCOPE 

four light spots, arranged in a square, with a craterlet in 
the middle, all of which undergo notable changes of aspect 
under different phases." 

Other writers also call attention to the fine markings, 
minute craterlets, and apparently changeable spots on the 
floor of Fracastorius. 

We go now to the eastern side of the Mare Nectaris, 
where we find one of the most stupendous formations in 
the lunar world, the great mountain ring of Theophilus, 
noticeably regular in outline and perfect in the complete- 
ness of its lofty wall. The circular interior, which con- 
tains in the center a group of mountains, one of whose 
peaks is 6,000 feet high, sinks 10,000 feet below the gen- 
eral level of the moon outside the wall! One of the peaks 
on the western edge towers more than 18,000 feet above 
the floor within, while several other peaks attain eleva- 
tions of 15,000 to 16,000 feet. The diameter of the immense 
ring, from crest to crest of the wall, is sixty-four miles. 
Theophilus is especially wonderful on the fifth and sixth 
days of the moon, when the sun climbs its shining pinna- 
cles and slowly discloses the tremendous chasm that lies 
within its circles of terrible precipices. 

On the southeast Theophilus is connected by exten- 
sions of its walls with a shattered ring of vast extent 
called Cyrillus; and south from Cyrillus, and connected 
with the same system of broken walls, lies the still larger 
ring named Catharina, whose half-ruined walls and numer- 
ous crater pits present a fascinating spectacle as the 
shadows retreat before the sunrise advancing across 
them. These three Theophilus, Cyrillus, and Catharina 
constitute a scene of surpassing magnificence, a glimpse 
of wonders in another world sufficient to satisfy the most 
riotous imagination. 

South of the Mare Nectaris the huge ring mountain of 



THE MOUNTAINS AND PLAINS OF THE MOON 171 

Piccolomini attracts attention, its massive walls sur- 
rounding a floor nearly sixty miles across, and rising 
in some places to an altitude of nearly 15,000 feet. It 
should be understood that wherever the height of the 
mountain wall of such a ring is mentioned, the refer- 
ence level is that of the interior plain or floor. The 
elevation, reckoned from the outer side, is always very 
much less. 

The entire region south and east of Theophilus and its 
great neighbors is marvelously rough and broken. Ap- 
proaching the center of the moon, we find a system of 
ringed plains even greater in area than any of those we 
have yet seen. Hipparchus is nearly a hundred miles 
long from north to south, and nearly ninety miles broad 
from east to west. But its walls have been destroyed 
to such an extent that, after all, it yields in grandeur to a 
formation like Theophilus. 

Albategnius is sixty-five miles across, with peaks from 
10,000 to 15,000 feet in height. Sacrobosco is a confused 
mass of broken and distorted walls. Aliacensis is re- 
markable for having a peak on the eastern side of its wall 
which is more than 16,000 feet high. Werner, forty-five 
miles in diameter, is interesting because under its north- 
eastern wall Miidler, some seventy years ago, saw a light 
spot of astonishing brightness, unmatched in that respect 
by anything on the moon except the peak of Aristarchus, 
which we shall see later. This spot seems afterward to 
have lost brilliance, and the startling suggestion has been 
made that its original brightness might have been due to 
its then recent deposit from a little crater that lies in the 
midst of it. Walter is of gigantic dimensions, about one 
hundred miles in diameter. Unlike the majority of the 
ringed plains, it departs widely from a circle. Stofler is 
yet larger than Walter; but most interesting of all these 



172 PLEASURES OF THE TELESCOPE 

gigantic formations is Maurolycus, whose diameter ex- 
ceeds one hundred and fifty miles, and which has walls 
13,000 or 14,000 feet high. Yet, astonishing though it 
may seem, this vast and complicated mass of mountain 
walls, craters, and peaks, is virtually unseen at full moon, 
owing to the perpendicularity of the sunlight, which pre- 
vents the casting of shadows. 

We shall next suppose that another period of about 
seven days has elapsed, the moon in the meantime reach- 
ing its full phase. We refer for guidance to Lunar Chart 
No. 3. The peculiarity of the northeastern quadrant 
which immediately strikes the eye is the prevalence of the 
broad plains called if aria, or " seas." The northern and 
central parts are occupied by the Mare Imbrium, the " Sea 
of Showers " or of " Rains," with its darljp bay the Sinus 
Mstuum, while the eastern half is covered by the vast 
Oceanus Procellarum, the " Ocean of Storms " or of " Tem- 
pests." 

Toward the north a conspicuous oval, remarkably dark 
in hue, immediately attracts our attention. It is the cele- 
brated ringed plain of Plato, about sixty miles in diameter 
and surrounded by a saw-edged rampart, some of whose 
pinnacles are 6,000 or 7,000 feet high. Plato is a favor- 
ite subject for study by selenographers because of the 
changes of color which its broad, flat floor undergoes as 
the sun rises upon it, and also because of the existence of 
enigmatical spots and streaks whose visibility changes. 
South of Plato, in the Mare Imbrium, rises a precipitous, 
isolated peak called Pico, 8,000 feet in height. Its resem- 
blance in situation to the conical mountain Pico in the 
Azores strikes the observer. 

Eastward of Plato a line of highlands, separating the 
Mare Imbrium from the Mare Frigoris, carries the eye to 
the beautiful semicircular Sinus Iridum, or " Bay of Rain- 



THE MOUNTAINS AND PLAINS OF THE MOON 173 



bows." The northwestern extremity of this remarkable 
bay is guarded by a steep and lofty promontory called 
Cape Laplace, while the southeastern extremity also has 
its towering guardian, Cape Heraclides. The latter is 



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LUNAR CHART No. 3, NORTHEAST QUARTER. 



interesting for showing, between nine and ten days after 
full moon, a singularly perfect profile of a woman's face 
looking out across the Mare Tmbrium. The winding lines, 
like submerged ridges, delicately marking the floor of the 
Sinus Iridum and that of the Mare beyond, are beautiful 



174 PLEASURES OF THE TELESCOPE 

telescopic objects. The " bay " is about one hundred and 
thirty-five miles long by eighty-four broad. 

The Mare Imlrium, covering 340,000 square miles, is 
sparingly dotted over with craters. All of the more con- 
spicuous of them are indicated in the chart. The smaller 
ones, like Caroline Herschel, Helicon, Leverrier, Delisle, 
etc, vary from eight to twelve miles in diameter. Lam- 
bert is seventeen miles in diameter, and Euler nineteen, 
while Timocharis is twenty-three miles broad and 7,000 
feet deep below its walls, which rise only 3,000 feet above 
the surface of the Mare. 

Toward the eastern border of the sea, south of the Har- 
binger Mountains, we find a most remarkable object, the 
mountain ring, or crater plain, called Aristarchus. This 
ring is not quite thirty miles in diameter, but there is 
nothing on the moon that can compare with it in dazzling 
brilliance. The central peak, 1,200 or 1,300 feet high, 
gleams like a mountain of crusted snow, or as if it were 
composed of a mass of fresh-broken white metal, or of com- 
pacted crystals. Part of the inner slope of the east wall is 
equally brilliant. In fact, so much light is poured out of 
the circumvallation that the eye is partially blinded, and 
unable distinctly to see the details of the interior. No 
satisfactory explanation of the extraordinary reflecting 
power of Aristarchus has ever been offered. Its neighbor 
toward the east, Herodotus, is somewhat smaller and 
not remarkably bright, but it derives great interest from 
the fact that out of a breach in its northern wall issues 
a vast cleft, or chasm, which winds away for nearly a 
hundred miles across the floor of the Mare, making an 
abrupt turn when it reaches the foot of the Harbinger 
Mountains. 

The comparatively small crater, Lichtenberg, near the 
northeastern limb of the moon, is interesting because Mad- 



THE MOUNTAINS AND PLAINS OF THE MOON 175 

ler used to see in its neighborhood a pale-red tint which 
has not been noticed since his day. 

Returning to the western side of the quadrant repre- 
sented in Lunar Chart No. 3, we see the broad and beauti- 
fully regular ringed plain of Archimedes, fifty miles in 
diameter and 4,000 feet deep. 

A number of clefts extend between the mountainous 
neighborhood of Archimedes and the feet of the gigantic 
Apennine Mountains on the southwest. The little double 
crater, Beer, between Archimedes and Timocharis, is very 
bright. 

The Apennines extend about four hundred and eighty 
miles in a northwesterly and southeasterly direction. 
One of their peaks near the southern end of the range, 
Mount Huygens, is at least 18,000 feet high, and the black 
silhouettes of their sharp-pointed shadows thrown upon 
the smooth floor of the Mare Imbrium about the time of 
first quarter present a spectacle as beautiful as it is 
unique. The Apennines end at the southeast in the ring 
mountain, Eratosthenes, thirty-eight miles across and 
very deep, one of its encircling chain of peaks rising 
16,000 feet above the floor, and about half that height 
above the level of the Mare Imbrium. The shadows cast 
by Eratosthenes at sunrise ar magnificent. 

And now we come to one of the supreme spectacles of 
the moon, the immense ring or crater mountain Coperni- 
cus. This is generally regarded as the grandest object 
that the telescope reveals on the earth's satellite. It is 
about fifty-six miles across, and its interior falls to a 
depth of 8,000 feet below the Mare Imbrium. Its broad 
wall, composed of circle within circle of ridges, terraces, 
and precipices, rises on the east about 12,000 feet above 
the floor. On the inner side the slopes are very steep, cliff 
falling below cliff, until the bottom of the fearful abyss is 



176 PLEASURES OF THE TELESCOPE 

attained. To descend th'ose precipices and reach the de- 
pressed floor of Copernicus would be a memorable feat for 
a mountaineer. In the center of the floor rises a compli- 
cated mountain mass about 2,400 'feet high. All around 
Copernicus the surface of the moon is dotted with count- 
less little crater pits, and splashed with whitish streaks. 
Northward lie the Carpathian Mountains, terminating on 
the east in Tobias Mayer, a ring mountain more than 
twenty miles across. The mountain ring Kepler, which is 
also the center of a great system of whitish streaks and 
splashes, is twenty-two miles in diameter, and notably 
brilliant. 

Finally, we turn to the southeastern quadrant of the 
moon, represented in Lunar Chart No. 4. The broad, 
dark expanse extending from the north is the Mare Nubium 
on the west and the Oceanus Procellarum on the east. To- 
ward the southeast appears the notably dark, rounded 
area of the Mare Humorum inclosed by highlands and 
rings. We begin with the range of vast inclosures run- 
ning southward near the central meridian, and starting 
with Ptolemseus, a walled plain one hundred and fifteen 
miles in its greatest diameter and covering an area con- 
siderably exceeding that of the State of Massachusetts. 
Its neighbor toward the south, Alphonsus, is eighty-three 
miles across. Next comes Arzachel, more than sixty-five 
miles in diameter. Thebit, more than thirty miles across, 
is very deep. East of Thebit lies the celebrated " lunar 
railroad," a straight, isolated wall about five hundred feet 
high and sixty-five miles long, dividing at its southern end 
into a number of curious branches, forming the buttresses 
of a low mountain. Purbach is sixty miles broad, and 
south of that comes a wonderful region where the ring 
mountains Hell, Ball, Lexell, and others, more or less 
connected with walls, inclose an area even larger than 



THE MOUNTAINS AND PLAINS OF THE MOON 177 



Ptolemseus, but which, not being so distinctly bordered as 
some of the other inclosed plains, bears no distinctive 
name. 

The next conspicuous object toward the south ranks 
with Copernicus among the grandest of all lunar phe- 



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ra^lT^IM^ NUBJUM 

^m Lassell 



Parry?: 



-' 



Damoiseau 
Flamsteed iQ 



^Landsbetyj 




LUNAR CHART No. 4, SOUTHEAST QUARTER. 



nomena the ring, or crater, Tycho. It is about fifty-four 
miles in diameter and some points on its wall rise 17,000 
feet above the interior. In the center is a bright moun- 



178 PLEASURES OF THE TELESCOPE 

tain peak 5,000 feet high. But wonderful as are the de- 
tails of its mountain ring, the chief attraction of Tycho is 
its manifest relation to the, mysterious bright rays hereto- 
fore referred to, which extend far across the surface of 
the moon in all directions, and of which it is the center. 
The streaks about Copernicus are short and confused, con- 
stituting rather a splash than a regular system of rays; 
but those emanating from Tycho are very long, regular, 
comparatively narrow, and form arcs of great circles which 
stretch away for hundreds of miles, allowing no obstacle to 
interrupt their course. 

Southwest of Tycho lies the vast ringed plain of Ma- 
ginus, a hundred miles broad and very wonderful to look 
upon, with its labyrinth of formations, when the sun 
slopes across it, and yet, like Maurolycus, invisible under 
a vertical illumination. " The full moon," to use Mad- 
ler's picturesque expression, " knows no Maginus." Still 
larger and yet more splendid is Clavius, which exceeds 
.one hundred and forty miles in diameter and covers 16,000 
square miles of ground within its fringing walls, which 
carry some of the loftiest peaks on the moon, several at- 
taining 17,000 feet. The floor is deeply depressed, so that 
an inhabitant of this singular inclosure, larger than Massa- 
chusetts, Connecticut, and Rhode Island combined, would 
dwell in land sunk two miles below the general level of 
the world about him. 

In the neighborhood of the south pole lies the large 
walled plain of Newton, whose interior is the deepest 
known depression on the moon. It is so deep that the sun- 
shine never touches the larger part of the floor of the 
inner abyss, and a peak on its eastern wall rises 24,000 
feet sheer above the tremendous pit. Other enormous 
walled plains are Longomontanus, Wilhelm I, Schiller, 
Bailly, and Schickard. The latter is one hundred and 



THE MOUNTAINS AND PLAINS OF THE MOON 179 

thirty-four miles long and bordered by a ring varying from 
4,000 to 9,000 feet in height. Wargentin, the oval close to 
the moon's southeast limb, beyond Schickard, is a unique 
formation in that, instead of its interior being sunk be- 
low the general level, it is elevated above it. It has been 
suggested that this peculiarity is due to the fact that the 
floor of Wargentin was formed by inflation from below, 
and that it has cooled and solidified in the shape of a 
gigantic dome arched over an immense cavity beneath. A 
dome of such dimensions, however, could not retain its 
form unless partly supported from beneath. 

Hainzel is interesting from its curious outline; Cichus 
for the huge yawning crater on its eastern wall; Capu- 
anus for a brilliant shining crater also on its eastern wall; 
and Mercator for possessing bright craters on both its 
east and its west walls. Vitello has a bright central 
mountain and gains conspicuousness from its position at 
the edge of the dark Mare Humorum. Agatharchides is 
the broken remnant of a great ring mountain. Gassendi, 
an extremely beautiful object, is about fifty-five miles 
across. It is encircled with broken walls, craters and 
and bright points, and altogether presents a 'very splen- 
did appearance about the eleventh day of the moon's age. 

Letronne is a half-submerged ring, at the southern end 
of the Oceanus Procellarum, which recalls Fracastorius in 
the western lunar hemisphere. It lies, however, ten de- 
grees nearer the equator than Fracastorius. Billy is a 
mountain ring whose interior seems to have been sub- 
merged by the dark substance of the Oceanus Procellarum, 
although its walls have remained intact. Mersenius is a 
very conspicuous ring, forty miles in diameter, east of the 
Mare Humorum. Vieta, fifty miles across, is also a fine 
object. Grimaldi, a huge dusky oval, is nearly one hun- 
dred and fifty miles in its greatest length. The ring moun- 



180 PLEASURES OF THE TELESCOPE 

tain Landsberg, on the equator, and near the center of 
the visible eastern hemisphere, is worth watching because 
Elger noticed changes of color in its interior in 1888. 

Bullialdus, in the midst of the Mare Nubium, is a very 
conspicuous and beautiful ring mountain about thirty- 
eight miles in diameter, with walls 8,000 feet high above 
the interior. 

Those who wish to see the lunar mountains in all their 
varying aspects will not content themselves with views 
obtained during the advance of the sunlight from west to 
east, between " new moon " and " full moon," but will con- 
tinue their observations during the retreat of the sunlight 
from east to west, after the full phase is passed. 

It is evident that the hemisphere of the moon which is 
forever turned away from the earth is quite as marvelous 
in its features as the part that we see. It will be noticed 
that the entire circle of the moon's limb, with insignificant 
interruptions, is mountainous. Possibly the invisible side 
of our satellite contains yet grander peaks and crater 
mountains than any that our telescopes can reach. This 
probability is increased by the fact that the loftiest 
known mountain on the moon is neyer seen except in sil- 
houette. It is a member of a great chain that breaks the 
lunar limb west of the south pole, and that is called the 
Leibnitz Mountains. The particular peak referred to is 
said by some authorities to exceed 30,000 feet in height. 
Other great ranges seen only in profile are the Dorfel 
Mountains on the limb behind the ring plain Bailly, the 
Cordilleras, east of Eichstadt, and the D'Alembert Moun- 
tains beyond Grimaldi. The profile of these great moun- 
tains is particularly fine when they are seen during an 
eclipse of the sun. Then, with the disk of the sun for a 
background, they stand out with startling distinctness. 



TEE SPECTACLES OF THE SUN 181 

THE SUN 

When the sun is covered with spots it becomes a most 
interesting object for telescopic study. Every amateur's 
telescope should be provided with apparatus for viewing 
the sun. A dark shade glass is not sufficient and not safe. 
What is known as a solar prism, consisting of two solid 
prisms of glass, cemented together in a brass box which 
carries a short tube for the eyepiece, and reflecting an im- 
age of the sun from their plane of junction while the 
major remnant of light and heat passes directly through 
them and escapes from an opening provided for the pur- 
pose serves very well. Better and more costly is an ap- 
paratus called a helioscope, constructed on the principle 
of polarization and provided with prisms and reflectors 
which enable the observer, by proper adjustment, to gov- 
ern very exactly and delicately the amount of light that 
passes into the eyepiece. 

Furnished with an apparatus of this description we 
can employ either a three-, four-, or five-inch glass upon the 
sun with much satisfaction. For the amateur's purposes 
the sun is only specially interesting when it is spotted. 
The first years of the twentieth century will behold a 
gradual growth in the number and size of the solar spots 
as those years happen to coincide with the increasing 
phase of the sun-spot period. Large sun spots and groups 
of spots often present an immense amount of detail which 
tasks the skill of the draughtsman to represent it. But a 
little practice will enable one to produce very good repre- 
sentations of sun spots, as well as of the whitish patches 
called faculse by which they are frequently surrounded. 

For the simple purpose of exhibiting the spotted face 
of the sun without much magnifying power, a telescope 
may be used to project the solar image on a white sheet or 



182 PLEASURES OF THE TELESCOPE 

screen. If the experiment is tried in a room, a little in- 
genuity will enable the observer to arrange a curtain cov- 
ering the window used, in such a way as to exclude all 
the light except that which comes" through the telescope. 
Then, by placing a sheet of paper or a drawing board be- 
fore the eyepiece and focusing the image of the sun upon 
it, very good results may be obtained. 

If one has a permanent mounting and a driving clock, 
a small spectroscope may be attached, for solar observa- 
tions, even to a telescope of only four or five inches aper- 
ture, and with its aid most interesting views may be ob- 
tained of the wonderful red hydrogen flames that fre- 
quently appear at the edge of the solar disk. 



CHAPTER X 

ARE THERE PLANETS AMONG THE STARS? 

"... And if there should be 
Worlds greater than thine own, inhabited 
By greater things, and they themselves far more 
In number than the dust of thy dull earth, 
What wouldst thou think ? " BYRON'S CAIN. 

THIS always interesting question has lately been re- 
vived in a startling manner by discoveries that have 
seemed to reach almost deep enough to touch its solution. 
The following sentences, from the pen of Dr. T. J. J. See, 
of the Lowell Observatory, are very significant from this 
point of view: 

" Our observations during 1896- ? 97 have certainly dis- 
closed stars more difficult than any which astronomers 
had seen before. Among these obscure objects about half 
a dozen are truly wonderful, in that they seem to be dark, 
almost black in color, and apparently are shining by a dull 
reflected light. It is unlikely that they will prove to be 
self-luminous. If they should turn out dark bodies in 
fact, shining only by the reflected light of the stars around 
which they revolve, we should have the first case of 
planets dark bodies noticed among the fixed stars." 

Of course, Dr. See has no reference in this state- 
ment to the immense dark bodies which, in recent years, 
have been discovered by spectroscopic methods revolving 
around some of the visible stars, although invisible them- 
selves. The obscure objects that he describes belong to 
a different class, and might be likened, except perhaps 

183 



184 PLEASURES OF THE TELESCOPE 

in magnitude, to the companion of Sirius, which, though a 
light-giving body, exhibits nevertheless a singular defect 
of luminosity in relation to its mass. Sirius has only 
twice the mass, but ten thousand-times the luminosity, of 
its strange companion! Yet the latter is evidently rather 
a faint, or partially extinguished, sun than an opaque 
body shining only with light borrowed from its dazzling 
neighbor. The objects seen by Dr. See, on the contrary, 
are " apparently shining by a dull reflected light." 

If, however (as he evidently thinks is probable), these 
objects should prove to be really non-luminous, it would 
not follow that they are to be regarded as more like the 
planets of the solar system than like the dark companions 
of certain other stars. A planet, in the sense which we 
attach to the word, can not be comparable in mass and 
size with the sun around which it revolves. The sun is a 
thousand times larger than the greatest of its attendant 
planets, Jupiter, and more than a million times larger 
than the earth. It is extremely doubtful whether the re- 
lation of sun and planet could exist between two bodies 
of anything like equal size, or even if one exceeded the 
other many times in magnitude. It is only when the dif- 
ference is so great that the smaller of the two bodies is 
insignificant in comparison with the larger, that the for- 
mer could become a cool, life-bearing globe, nourished by 
the beneficent rays of its organic comrade and master. 

Judged by our terrestrial experience, which is all we 
have to go by, the magnitude of a planet, if it is to bear 
life resembling that of the earth, is limited by other con- 
siderations. Even Jupiter, which, as far as our knowl- 
edge extends, represents the extreme limit of great plan- 
etary size, may be too large ever to become the abode of 
living beings of a high organization. The force of gravi- 
tation on the surface of Jupiter exceeds that on the 



ARE THERE PLANETS AMONG THE STARS? 185 

earth's surface as 2.64 to 1. Considering the effects of 
this on the weight and motion of bodies, the density of the 
atmosphere, etc., it is evident that Jupiter would, to say 
the very least, be an exceedingly uncomfortable place of 
abode for beings resembling ourselves. But Jupiter, if 
it is ever to become a solid, rocky globe like ours, must 
shrink enormously in volume, since its density is only 0.24 
as compared with the earth. Now, the surface gravity of 
a planet depends on its mass and its radius, being directly 
as the former and inversely as the square of the latter. 
But in shrinking Jupiter will lose none of its mass, al- 
though its radius will become much smaller. The force of 
gravity will consequently increase on its surface as the 
planet gets smaller and more dense. 

The present mean diameter of Jupiter is 86,500 miles, 
while its mass exceeds that of the earth in the ratio of 316 
to 1. Suppose Jupiter shrunk to three quarters of its 
present diameter, or 64,800 miles, then its surface gravity 
would exceed the earth's nearly five times. With one half 
its present diameter the surface gravity would become 
more than ten times that of the earth. On such a planet 
a man's bones would snap beneath his weight, even grant- 
ing that he could remain upright at all! It would seem, 
then, that, unless we are to abandon terrestrial analogies 
altogether and " go it blind," we must set an upper limit 
to the magnitude of a habitable planet, and that Jupiter 
represents such upper limit, if, indeed, he does not tran- 
scend it. 

The question then becomes, Can the faint objects seen 
by Dr. See and his fellow-observers, in the near neighbor- 
hood of certain stars, be planets in the sense just de- 
scribed, or are they necessarily far greater in magnitude 
than the largest planet, in the accepted sense of that word, 
which can be admitted into the category viz., the planet 

13 



186 PLEASURES OF THE TELESCOPE 

Jupiter? This resolves itself into another question: At 
what distance would Jupiter be visible with a powerful 
telescope, supposing it to receive from a neighboring star 
an amount of illumination not les than that which it gets 
from the sun? To be sure, we do not know how far away 
the faint objects described by Dr. See are; but, at any rate, 
we can safely assume that they are at the distance of 
the nearest stars, say somewhere about three hundred 
thousand times the earth's distance from the sun. The 
sun itself removed to that distance would appear to our 
only as a star of the first magnitude. But Zollner 
shown that the sun exceeds Jupiter in brilliancy 
5,472,000,000 times. Seen from equal distances, however, 
the ratio would be about 218,000,000 to 1. This would be 
the ratio of their light if both sun and Jupiter could be 
removed to about the distance of the nearest stars. Since 
the sun would then be only as bright as one of the 
stars of the first magnitude, and since Jupiter would be 
218,000,000 times less brilliant, it is evident that the latter 
would not be visible at all. The faintest stars that the 
most powerful telescopes are able to show probably do 
not fall below the sixteenth or, at the most, the seven- 
teenth magnitude. But a seventeenth-magnitude star i& 
only between two and three million times fainter than the 
sun would appear at the distance above supposed, while, 
as we have seen, Jupiter would be more than two hundred 
million times fainter than the sun. 

To put it in another way: Jupiter, at the distance of 
the nearest stars, would be not far from one hundred 
times less bright than the faintest star which the largest 
telescope is just able, under the most exquisite conditions, 
to glimpse. To see a star so faint as that would require 
an object-glass of a diameter half as great as the length 
of the tube of the Lick telescope, or say thirty feet! 



ARE THERE PLANETS AMONG THE STARS f 187 

Of course, Jupiter might be more brilliantly illumi- 
nated by a brighter star than the sun; but, granting that, 
it still would not be visible at such a distance, even if we 
neglect the well-known concealing or blinding effect of the 
rays of a bright star when the observer is trying to view a 
faint one close to it. Clearly, then, the obscure objects 
seen by Dr. See near some of the stars, if they really are 
bodies visible only by light reflected from their surfaces, 
must be enormously larger than the planet Jupiter, and 
can not, accordingly, be admitted into the category of 
planets proper, whatever else they may be. 

Perhaps they are extreme cases of what we see in the 
system of Sirius i. e., a brilliant star with a companion 
which has ceased to shine as a star while retaining its 
bulk. Such bodies may be called planets in that they only 
shine by reflected light, and that they are attached to a 
brilliant sun; but the part that they play in their systems 
is not strictly planetary. Owing to their great mass they 
bear such sway over their shining companions as none of 
our planets, nor all of them combined, can exercise; and 
for the same reason they can not, except in a dream, be 
imagined to possess that which, in our eyes, must always 
be the capital feature of a planet, rendering it in the 
highest degree interesting wherever it may be found- 
sentient life. 

It does not follow, however, that there are no real 
planetary bodies revolving around the stars. As Dr. See 
himself remarks, such insignificant bodies as our planets 
could not be seen at the distance of the fixed stars, " even 
if the power of our telescopes were increased a hundred- 
fold, and consequently no such systems are known." 

This brings me to another branch of the subject. In 
the same article from which I have already quoted (Recent 
Discoveries respecting the Origin of the Universe, Atlantic 



188 PLEASURES OF THE TELESCOPE 

Monthly, vol. Ixxx, pages 484-492), Dr. See sets forth the 
main results of his well-known studies on the origin of the 
double and multiple star systems. He finds that the stel- 
lar systems differ from the solar system markedly in two 
respects, which he thus describes: 

"1. The orbits are highly eccentric; on the average 
twelve times more elongated than those of the planets and 
satellites. 

" 2. The components of the stellar systems are fre- 
quently equal and always comparable in mass, whereas 
our satellites are insignificant compared to their plan- 
ets, and the planets are equally small compared to the 
sun." 

These peculiarities of the star systems Dr. See ascribes 
to the effect of " tidal friction," the double stars having 
had their birth through fission of original fluid masses 
(just as the moon, according to George Darwin's theory, 
was born from the earth), and the reaction of tidal fric- 
tion having not only driven them gradually farther apart 
but rendered their orbits more and more eccentric. This 
manner of evolution of a stellar system Dr. See contrasts 
with Laplace's hypothesis of the origin of the planetary 
system through the successive separation of rings from 
the periphery of the contracting solar nebula, and the 
gradual breaking up of those rings and their aggregation 
into spherical masses or planets. While not denying that 
the process imagined by Laplace may have taken place 
in our system, he discovers no evidence of its occurrence 
among the double stars, and this leads him to the follow- 
ing statement, in which believers in the old theological 
doctrine that the earth is the sole center of mortal life and 
of divine care would have found much comfort: 

" It is very singular that no visible system yet dis- 
cerned has any resemblance to the orderly and beautiful 



ARE THERE PLANETS AMONG THE STARS? 189 

system in which we live; and one is thus led to think that 
probably our system is unique in its character. At least 
it is unique among all known systems." 

If we grant that the solar system is the only one in 
which small planets exist revolving around their sun in 
nearly circular orbits, then indeed we seem to have closed 
all the outer universe against such beings as the inhabit- 
ants of the earth. Beyond the sun's domain only whirling 
stars, coupled in eccentric orbits, dark stars, some of them, 
but no planets in short a wilderness, full of all energies 
except those of sentient life! This is not a pleasing pic- 
ture, and I do not think we are driven to contemplate it. 
Beyond doubt, Dr. See is right in concluding that double 
and multiple star systems, with their components all of 
magnitudes comparable among themselves, revolving in 
exceedingly eccentric orbits under the stress of mutual 
gravitation, bear no resemblance to the orderly system of 
our sun with its attendant worlds. And it is not easy to 
imagine that the respective members of such systems 
could themselves be the centers of minor systems of 
planets, on account of the perturbing influences to which 
the orbits of such minor systems would be subjected. 

But the double and multiple stars, numerous though 
they be, are outnumbered a hundred to one by the single 
stars which shine alone as our sun does. What reason 
can we have, then, for excluding these single stars, consti- 
tuting as they do the vast majority of the celestial host, 
from a similarity to the sun in respect to the manner of 
their evolution from the original nebulous condition? 
These stars exhibit no companions, such planetary at- 
tendants as they may have lying, on account of their 
minuteness, far beyond the reach of our most powerful in- 
struments. But since they vastly outnumber the binary 
and multiple systems, and since they resemble the sun in 



190 PLEASURES OF TEE TELESCOPE 

having no large attendants, should we be justified, after 
all, in regarding our system as " unique "? It is true we 
do not know, by visual evidence, that the single stars have 
planets, but we find planets attending the only representa- 
tive of that class of stars that we are able .to approach 
closely the sun and we know that the existence of 
those planets is no mere accident, but the result of the 
operation of physical laws which must hold good in every 
instance of nebular condensation. 

Two different methods are presented in which a rotat- 
ing and contracting nebula may shape itself into a stellar 
or planetary system. The first is that described by La- 
place, and generally accepted as the probable manner of 
origin of the solar system viz., the separation of rings 
from the condensing mass, and the subsequent transfor- 
mation of the rings into planets. The planet Saturn is 
frequently referred to as an instance of the operation of 
this law, in which the evolution has been arrested after 
the separation of the rings, the latter having retained the 
ring form instead of breaking and collecting into globes, 
forming in this case rings of meteorites, and reminding us 
of the comparatively scattered rings of asteroids sur- 
rounding the sun between the orbits of Mars and Jupiter. 
This Laplacean process Dr. See regards as theoretically 
possible, but apparently he thinks that if it took place it 
was confined to our system. 

The other method is that of the separation of the 
original rotating mass into two nearly equal parts. The 
mechanical possibility of such a process has been proved, 
mathematically, by Poincare' and Darwin. This, Dr. See 
thinks, is the method which has prevailed among the 
stars, and prevailed to such a degree as to make the solar 
system, formed by the ring method, probably a unique 
phenomenon in the universe. 



ARE THERE PLANETS AMONG TEE STARS? 191 

Is it not more probable that both methods have been 
in operation, and that, in fact, the ring method has oper- 
ated more frequently than the other? If not, why do the 
single stars so enormously outnumber the double ones? 
It is of the essence of the fission process that the resulting 
masses should be comparable in size. If, then, that pro- 
cess has prevailed in the stellar universe to the practical 
exclusion of the other, there should be very few single 
stars; whereas, as a matter of fact, the immense majority 
of the stars are single. And, remembering that the sun 
viewed from stellar distances would appear unattended 
by subsidiary bodies, are we not justified in concluding 
that its origin is a type of the origin of the other single 
stars? 

While it is, as I have remarked, of the essence of the 
fission process that the resulting parts of the divided mass 
should be comparable in magnitude, it is equally of the 
essence of the ring, or Laplacean process, that the bodies 
separated from the original mass should be comparatively 
insignificant in magnitude. 

As to the coexistence of the two processes, we have, 
perhaps, an example in the solar system itself. Darwin's 
demonstration of the possible birth of the moon from the 
earth, through fission and tidal friction, does not apply to 
the satellites attending the other planets. The moon is 
relatively a large body, comparable in that respect with 
the earth, while the satellites of Jupiter and Saturn, for 
instance, are relatively small. But in the case of Saturn 
there is visible evidence that the ring process of satellite 
formation has prevailed. The existing rings have not 
broken up, but their very existence is a testimony of the 
origin of the satellites exterior to them from other rings 
which did break up. Thus we need not go as far away 
as the stars in order to find instances illustrating both 



192 PLEASURES OF THE TELESCOPE 

the methods of nebular evolution that we have been deal- 
ing with. 

The conclusion, then, seems to be that we are not justi- 
fied in assuming that the solar system is unique simply 
because it differs widely from the double and multiple 
star systems; and that we should rather regard it as 
probable that the vast multitude of stars which do not 
appear, when viewed with the telescope, or studied by 
spectroscopic methods, to have any attendants compara- 
ble with themselves in magnitude, have originated in a 
manner resembling that of the sun's origin, and may be 
the centers of true planetary systems like ours. The 
argument, I think, goes further than to show the mere 
possibility of the existence of such planetary systems sur- 
rounding the single stars. If those stars did not origi- 
nate in a manner quite unlike the origin of the sun, then 
the existence of planets in their neighborhood is almost 
a foregone conclusion, for the sun could hardly have 
passed through the process of formation out of a rotating 
nebula without evolving planets during its contraction. 
And so, notwithstanding the eccentricities of the double 
stars, we may still cherish the belief that there are eyes 
to see and minds to think out in celestial space. 



INDEX 



NOTE. Double, triple, multiple, and colored stars, star clusters, nebulae, and temporary 
stars will be found arranged under the heads of their respective constellations. 



ANDROMEDA, Map No. 24, 125. 
Stars : o, 126. 
7, 128. 
/t, 126. 
36, 128. 

Temporary star : 1885, 127. 
Cluster : 457, 128. 
Variable : R, 128. 
Nebula : 116, 126. 
AQUARIUS, Map No. 18, 107. 
Stars : 106. 
T, 108. 
*, 108. 
41, 106. 
2 2729, 106. 
2 2745 (12), 106. 
2 2998, 108. 
Variables: R, 108. 
S, 108. 
T, 106. 
Nebute : 4628 (Rosse's " Saturn "), 108. 

4678, 108. 

AQUILA, Map No. 16, 95. 
Stars : , 94. 
11, 94. 
23, 94. 
57, 94. 
2 2644, 94. 
2 2544, 94. 
Cluster : 4440, 94. 
Variables : 17, 94. 
R, 94. 

ARGO : Map No. 2, 31 ; Map No. 7, 55. 
Stars : 2 1097, 33. 

2 1146 (5), 35. 
Clusters : 1551, 35. 



Clusters : 1564, 35. 
1571, 35. 
1630, 56. 

Nebula : 1564, 35. 
ARIES, Map No. 22, 119. 
Stars : 7, 118. 
, 120. 
X, 118. 

IT, 118. 

14, 118. 
30, 118. 
41, 118. 
52, 120. 
2 289, 118. 

AURIGA, Map No. 5, 45. 
Stars : a (Capella), 44. 

(Menkalina), 46. 
e, 50. 

0, 48. 
\, 50. 
14, 50. 
26, 50. 
41, 51. 

2 616, 48. 

Temporary star : 1892, 48. 
Clusters : 996, 51. 
1067, 51. 
1119, 51. 
1166, 51. 
1295, 48. 

BOOTES, Map No. 11, 67. 
Stars : a (Arcturus), 66. 
8, 71. 

e (Mirac), 71. 
70. 

1, 71. 

193 



194: 



PLEASURES OF THE TELESCOPE 



Stars : , 71. 
A*, 71. 

e,m 

IT, 70. 

2 1772, 70. 
2 1890 (39), 71. 
2 1909 (44), 71. 
2 1910 (279), 70. 
2 1926, 71. 

CAMELOPARDALUS, Map No. 25, 133. 
Stars : 1, 134. 
2, 134. 
7, 135. 
2 385, 134. 
2 390, 134. 
Cluster : 940, 135. 
CANES VENATICI, Map No. 26, 137 ; Map 

No. 11, 67. 
Stars: 2,136. 

12 (Cor Caroli), 136. 
2 1606, 136. 
2 1768 (25), 72. 
Cluster : 3936, 72. 
Nebula : 3572, 136. 
CANIS MAJOR, Map No. 2, 31. 
Stars : a (Sirius), 30. 
5,33. 
/t,33. 

Clusters : 1454, 33. 
1479, 33. 
1512, 33. 
Variable : 7, 33. 
Nebula : 1511, 33. 
CANIS MINOR, Map No. 3, 34. 
Stars : a (Procyon), 36. 
14, 36. 

2 1126 (31 Can. Min. Bode), 36. 
CANCER, Map No. 4, 39. 
Stars : 43. 
*, 44. 
66,44. 
2 1223, 44. 
2 1291, 44. 
2 1311, 44. 
Clusters : Praesepe, 43. 

1712, 44. 

CAPRICORNUS, Map No. 13, 83 ; Map No. 
18, 107. 



Stars : a, 84. 

0, 85. 
o,85. 
*, 85. 

| P, 85. 
<r,85. 

Cluster : 4608, 85. 
CASSIOPEIA, Map No. 25, 133. 
Stars : i\, 132. 

1, 132. 
<r, 132. 
*, 132. 

Temporary star: 1572 (Tycho's), 

134. 

Cluster : 392, 134. 
CEPHEUS, Map No. 25, 133. 
CETUS, Map No. 20, 112. 
Stars: o, 113. 
7, 113. 

'Cm. 

*?, HI. 
26, 111. 
42, 111. 

Variables : o (Mira), 111. 
R, 113. 
S, 113. 

COLUMBA, Map No. 2, 31. 
COMA BERENICES, Map No. 6, 53. 
Stars: 2,54. 
12, 54. 
17, 54. 
24,54. 
35, 54. 
42, 54. 
Clusters : 2752, 56. 

3453, 56. 

CORONA BOREALIS, Map No. 11, 67. 
Stars : 7, 72. 



v, 73. 
<r, 73. 

2 1932, 72. 

Temporary star : 1866, 73. 
CORVUS, Map No. 8, 58. 

Star : 8, 57. 

CRATER, Map No. 8, 58. 
Variable : R, 57. 



INDEX 



195 



CYGNUS, Map No. 17, 99. 


Stars : 7, 43. 


Stars: (Albireo), 103. 


5,41. 


8, 104. 


6,43. 


A, 105. 


6.41 


p, 105. 


1,42. 


o, 104. 


K, 40. 


X (17), 104. 


A, 43. 


^, 104. 


M ,43. 


49, 104. 


ir, 40. 


52, 104. 


15, 43. 


61, 105. 


38, 43. 


Temporary star : 1876, 105. 


Cluster: 1360,42. 


Cluster : 4681, 105. 


Variables : 41. 


Variable : x 104. 


TJ, 42. 


DELPHINUS, Map No. 16, 95. 


E, 41. 


Stars: a, 96. 


8,41. 


0,96. 


T, 41. 


7,94. 


U,41. 


DRACO, Map No. 15, 91 ; Map No. 26, 137. 


Nebula: 1532,41. 


Stars : 7, 93. 


HERCULES, Map No. 14, 87 ; Map No. 15, 


6,93. 


91. 


* 93. 


Stars : a, 89. 


A*, 93. 


7,89. 


v, 93. 


5, 89. 


2 1984, 93. 


89. 


2 2054, 93. 


, 89. 


2 2078 (17), 93. 


/x,90. 


2 2323, 93. 


p, 90. 


Nebula: 4373,93. 


42, 90. 


4415, 94. 


95, 90. 


EQUULEUS, Map No. 18, 107. 


2 2101, 90. 


Stars : 0, 109. 


2 2104, 90. 


7, 109. 


2 2215, 90. 


2 2735, 108. 


2 2289, 90. 


2 2737, 108. 


Nebulae : 4230 (M 13), 92. 


2 2742, 108. 


4234, 92. 


2 2744, 108. 


HYDRA, Map No. 3, 34; Map No. 8, 58; 


ERIDANUS, Map No. 21, 115. 


Map No. 10, 65. 


Stars : 7, 114. 


Stars : o, 56. 


o 2 , 116. 


6,36. 


12, 114. 


0,36. 


2 470 (32), 114. 


Bu. 339, 56. 


2 516 (39), 114. 


2 1245, 36. 


2 590, 116. 


Variable : R, 59. 


Nebula: 826, 116. 


Nebulas : 2102, 56. 


GEMINI, Map No. 4, 39. 


3128, 59. 


Stars : a (Castor), 38. 


LACERTA, Map No. 17, 99. 


(Pollux), 40. 


LEO, Map No. 6, 53. 



196 PLEASURES OF THE TELESCOPE 


Stars: 7, 52. 


Stars : 2 1183, 35. 


i, 52. 


2 1190, 35. 


T, 52. 


Clusters : 1424, 35. 


49,52. 


1465, 36. 


54, 52. 


1483, 36. 


88, 52. 


1611, 36. 


90, 52. 


1637, 36. 


Variable : R, 52. 


Variable : S, 35. 


Nebula: 1861,52. 


OPHIUCHUS, Map No. 12, 77; Map No. 


LEO MINOR, Map No. 26, 137. 


14, 87. 


LEPUS, Map No. 1, 21 ; Map No. 2, 31. 


Stars : A, 86. 


Stars : o, 30. 


T, 86. 


0,30. 


36, 79. 


7,30. 


39, 79. 


i,30. 


67, 86. 


45, 30. 


70, 86. 


Variable: R, 29. 


73, 86. 


LIBRA, Map No. 10, 65. 


2 2166, 86. 


Stars : A, 64. 


2 2173, 86. 


a, 64. 


Temporary star : 1604, 80. 


0,64. 


Clusters: 4211, 79. 


i,64. 


4256, 88. 


Variable : 8, 64. 


4264, 79. 


LYNX, Map No. 5, 45. 


4268, 79. 


Stars : 4, 51. 


4269, 79. 


5,51. 


4270, 79. 


12, 51. 


4315, 88. 


14, 51. 


4346, 79. 


19, 51. 


4410, 88. 


38, 52. 


Variable : R, 80. 


2 958, 51. 


ORION, Map No. 1, 21. 


2 1009, 51. 


Stars : a (Betelgeuse), 27. 


2 1333, 51. 


(Rigel), 20. 


LYRA, Map No. 17, 99. 


8,23. 


Stars : a (Vega), 97. 


C,23. 


0,100. 


T;, 24. 


e, 98. 


(Trapezium), 25. 


100. 


,27. 


17, 103. 


A, 28. 


Variable : 0, 100. 


P, 28. 


Nebula: 4447 (Ring), 102. 


<r,24. 


MONOCEROS, Map No. 1, 21 ; Map No. 3, 34. 


T, 28. 


Stars : 4, 35. 


f>, 29. 


8,35. 


2 627, 28. 


11, 35. 


2 629, 28. 


2 921, 35. 


2 652, 28. 


2 938, 35. 


2 725, 24. 


2 950, 35. 


2 728 (A 32), 28. 



INDEX 



197 



Stars : 2 729, 29. 
2 747, 27. 
2 750, 27. 
2 795 (52), 27. 
2 816, 29. 
2 98 (i), 28. 
Clusters : 905, 29. 
1184, 27. 
1361, 29. 
1376, 29. 

Nebula : Great Orion Nebula, 25. 
1227, 23. 
1267, 29. 

PEGASUS, Map No. 19, 110. 

Stars : 0, 109. 

7, 109. 

e, 109. 

TJ, 109. 

PERSEUS, Map No. 24, 125. 
Stars : e, 129. 
C, 130. 
rj, 129. 

Clusters : 512, 129. 
521, 129. 

Variable : & (Algol), 130. 
PISCES, Map No. 18, 107; Map No. 20, 

112 ; Map No. 22, 119. 
Stars : a, 117. 
117. 
*, H7. 
55, 117. 
65, 117. 
66, 117. 
77, 117. 

Variable : R, 118. 
SAGITTA, Map No. 16, 95. 
Stars : e, 94. 
C,94. 
0,94. 

Nebula : 4572, 94. 
SAGITTARIUS, Map No. 12, 77 ; Map No. 

13, 83. 
Stars : /i, 80. 

54, 84. 

Clusters : M 25, 81. 
4355, 81. 
4361 (M 8), 81. 
4397 (M 24), 81. 



Clusters : 4424, 84. 

Variables : R, 84. 

T, 84. 

U, 82. 

V, 82. 

SCORPIO, Map No. 12, 77. 
Stars : a (Antares), 75. 
ft 76. 
v, 76. 
1,76. 
tr, 76. 

Temporary star : 1860, 78. 
Clusters : 4173, 78. 
4183, 78. 
SCUTUM SOBIESKH, Map No. 12, 77 ; Map 

No. 13, 83. 
Stars: 22306,82. 
2 2325, 82. 
Clusters : 4400, 82. 
4426, 82. 
4437, 82. 
Variable : R, 82. 
Nebula : 4441, 82. 
SERPENS, Map No. 12, 77 ; Map No. 14, 

87. 

Stars : a, 86. 
ft 86. 
8,86. 
0,88. 
v, 86. 

Variable : R, 86. 
TAURUS, Map No. 23, 121. 
Stars : a (Aldebaran), 123. 
TJ (Alcyone), 120. 
0, 123." 
K, 123. 
<r, 124. 
T, 124. 
<J>, 123. 
X, 123. 
30, 122. 
2 412 (7), 120. 
2 430, 122. 
2 674, 124. 
2 716, 124. 

Clusters: Hyades, 120. 
Pleiades, 120. 
1030, 124. 



198 



PLEASURES OF THE TELESCOPE 



Variable : \, 122. 
Nebulae : in Pleiades, 120. 

1157 (Crab Net), 124. 
TRIANGULUM, Map No. 24, 125. 
Star: 6, 129. 
Nebula : 352, 129. 
URSA MAJOR. 
Stars: (Mizar), 135. 
i, 135. 
v, 135. 
f, 135. 
<r 2 , 135. 
23, 135. 
57, 135. 
65, 135. 

Nebulas : 1949, 136. 
1950, 136. 
2343, 136. 

URSA MINOR, Map No. 26, 137. 
Stars : a (Pole Star), 138. 

IT, 138. 

VIRGO, Map No. 9, 61. 
Stars : a (Spica), 59. 
7,59. 
0,60. 
84, 62. 
2 1669, 59. 
' 21846,62. 
Variables : R, 63. 
S, 63. 
U, 63. 

Nebulas : Field of the, 62. 
2806, 63. 
2961, 63. 
3105, 63. 

VULPECTTLA, Map No. 17, 99. 
Star: 22695, 106. 
Temporary star : 1670, 106. 
Nebula : 4532 (Dumb Bell), 106. 
THE MOON, most interesting of telescopic 
objects, 156; telescopic views of 
moon reversed, 157. 
Craters, ring mountains, and ringed 
plains : 

Agatharchides, 179. 
Agrippa, 168. 
Albategnius, 171. 
Alhazen, 160. 



Aliacensis, 171. 
Alphonsus, 176. 
Archimedes, 175. 
Ariadaaus, 168. 
Aristarchus, 174. 
Aristillus, 167. 
Aristoteles, 162. 
Arzachel, 176. 
Atlas, 160. 
Autolycus, 167. 
Bailly, 178. 
Ball, 176. 
Barrow, 162. 
Beer, 175. 
Berzelius, 160. 
Billy, 179. 
Bullialdus, 180. 
Burckhardt, 157. 
Capuanus, 179. 
Cassini, 167. 
Catharina, 170, 
Cichus, 179. 
Clavius, 178. 
Cleomenes, 159. 
Condorcet, 160. 
Copernicus, 175. 
Cyrillus, 170. 
Delisle, 174. 
Endymion, 160. 
Eratosthenes, 175. 
Eudoxus, 162. 
Euler, 174. 
Firmicus, 160. 
Fracastorius, 169, 179. 
Furnerius, 161. 
Gassendi, 179. 
Gauss, 159. 
Geminus, 160. 
Goclenius, 169. 
Godin, 168. 
Grimaldi, 179. 
Guttemberg, 169. 
Hainzel, 179. 
Hansen, 160. 
Helicon, 174. 
Hell, 176. 
Hercules, 160. 
Herodotus, 174. 



INDEX 



199 



Herschel, Caroline, 174. 
Hipparchus, 171. 
Humboldt, 161. 
Hyginus, 168. 
Julius Caesar, 168. 
Kepler, 176. 
Lambert, 174 
Landsberg, 180. 
Langrenus, 160, 168. 
Letronne, 179. 
Leverrier, 174. 
Lexell, 176. 
Lichtenberg, 174. 
Linne, 165. 
Longoraontanus, 178. 
Macrobius, 159. 
Maginus, 178. 
Manilius, 166. 
Maurolycus, 172. 
Menelaus, 166. 
Mercator, 179. 
Mersenius, 179. 
Messala, 160. 
Messier, 169. 
Newton, 178. 
Petavius, 160, 168. 
Picard, 157. 
Piccolomini, 171. 
Pico, 172. 
Plato, 172. 
Plinius, 166. 
Posidonius, 163, 164. 
Proclus, 158. 
Ptoleraaaus, 176. 
Purbach, 176. 
Sacrobosco, 171. 
Schickard, 178. 
Schiller, 178. 
Silberschlag, 168. 
Stofler, 171. 
Sulpicius Gallus, 166. 
Theaetetus, 167. 
Thebit, 176. 
Theophilus, 170. 
Timocharis, 174. 
Tobias Mayer, 176. 
Tralles, 159. 
Triesnecker, 168. 



Tycho, 177, 178. 

Vendelinus, 160, 168. 

Vieta, 179. 

Vitello, 179. 

Walter, 171. 

Wargentin, 179. 

Werner, 171. 

Wilhelm I, 178. 
Maria, or " Seas " : 

Lacus Somniorum, 163. 

Mare Crisium, 157, 159, 160. 

Mare Fecunditatis, 160, 168. 

Mare Frigoris, 162, 172. 

Mare Humboldtianum, 160. 

Mare Humorum, 176, 179. 

Mare Imbrium, 163, 172, 174. 

Mare Nectaris, 168. 

Mare Nubium, 176. 

Mare Serenitatis, 163, 164, 165. 

Mare Tranquilitatis, 168. 

Mare Vaporum, 166, 167. 

Oceanus Procellarum, 172, 176 r 
179. 

Palus Nebularum, 167. 

Palus Putredinis, 167. 

Palus Somnii, 159. 

Sinus ^Estuum, 172. 

Sinus Iridum, 172, 173. 
Other formations : 

Alps Mountains, 163. 

Apennine Mountains, 163, 167, 175, 

Cape Agarum, 158. 

Cape Heraclides, 173. 

Cape Laplace, 173. 

Carpathian Mountains, 176. 

Caucasus Mountains, 163. 

Cordilleras Mountains, 180. 

D'Alembert Mountains, 180. 

DOrfel Mountains, 180. 

Haemus Mountains, 165. 

Harbinger Mountains, 174. 

Leibnitz Mountains, 180. 

" Lunar Railroad," 176. 

Mt. Argjeus, 165, 167. 

Mt, Hadley, 167. 

Mt. Huygeus, 175. 

Pyrenees Mountains, 169. 

Taurus Mountains, 164. 



200 



PLEASURES OF TEE TELESCOPE 



THE PLANETS : Are there planets among 

the stars? 183. 
Mars, two views of, 17. 

best advertised of planets, 151. 

favorable oppositions of, 152. 

seen with 5-inch telescope, 152. 

polar caps of, 152. 
color of, 152. 

dark markings on, 152. 
"canals," 153. 

earthlike condition of, 153. 
Mercury, phases of, 155. 

peculiar rotation of, 155. 

markings on, 155. 

probably not habitable, 155. 
Jupiter, easiest planet for amateurs, 141. 

seen with 5-inch glass, 141. 

satellites, swift motions of, 142. 

velocity of planet's equator, 142. 

how to see all sides of, 142, 143. 

watching rotation of, 143. 

eclipses and transits of satellites, 
144, 147. 

belts and clouds of, 145. 

different rates of rotation, 145. 

names and numbers of satellites, 146. 
Saturn, next to Jupiter in attractive- 
ness, 147. 

seen with 5-inch glass, 148. 

its moons and their orbits, 148, 149. 

polar view of system, 149. 

Roche's limit, 149, 150. 



Saturn, origin of the rings, 150. 

Pickering's ninth satellite, 151. 

the satellites as telescopic objects, 

151. 
Venus^her wonderful brilliance, 153. 

her atmosphere seen, 153. 

Lowell's observations, 153. 

Schiaparelli's observations, 154. 

her peculiar rotation, 154. 

how to see, in daytime, 155. 
Neptune and Uranus, 155. 
THE SUN, 181. 
shade glasses for telescopes in viewing, 

181. 

solar prism, 181. 
helioscope, 181. 
periodicity of spots, 181. 
to see, by projection, 182. 
spectroscope for solar observation, 182. 
THE TELESCOPE: 
refractors and reflectors, 2, 8. 
eyepieces, 6, 9, 10. 
aberration (chromatic), 6; (spherical), 

6,17. 
achromatic telescopes, how made, 7. 

object glass, 8. 
magnifying power, 11. 
mountings, 12. 
rules for testing, 13. 
image of star in, 14. 
image in and out of focus, 14, 15, 17. 
astigmatism, 16. 



THE END 



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General Library 

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1692 S. Pleasures of the Telescope GARRET? P. SERWSS 

This book says to the amateur, in effect: "What if you have not all 
advantages of clock-work and observatory equipment. You may know some- 
thing of the witchery of the heavens even with a little telescope of three to five 
inches aperture ! " "Pleasures of the Telescope " is popular in style rather 
than technical. For setting forth ' ' the chief attractions of the starry heavens, " 
a complete set of star-maps is included, showing " all the stars visible to the 
naked eye in the regions of sky represented, and in addition some stars that 
can only be seen with optical aid." In six chapters these twenty-six maps are 
described so plainly that the amateur can readily find all the interesting star- 
groups, clusters, and nebulae, and also the colored or double stars. In the 
three concluding chapters the moon and planets receive special consideration. 
In the opening chapter the amateur is told how to select and test a glass. 

Booklovers Bulletin.