HOW 18 SHE HEADINGS 223
The observer is supposed to be standing at the centre of the compass,
shown in Diagram 2, which is also the centre of his horizon, the points
of the compass radiating outwards towards the sea horizon. There are
five examples given and it is required to know, in each case, between
what points the other vessel is heading when one of her side-lights is
sighted on a given bearing. Let us discuss each example separately.
1. A. Both side-lights bearing North? The vessel can only be
heading South.
B Green light bearing North. When the vessel turns her head to
port from position A she shuts out her red light; the observer
will see only her green light until she has swung through 10
points, that is, when she heads E.N.E., for then the observer will
be 2 points abaft her beam and the green light will then disappear.
Rule.—Count 6 points to Starboard of the bearing for a Green light,
or, 6 points to Port of the bearing for a Red light, and the vessel will be
heading somewhere between that direction and the Bearing Reversed
nearly.
The green light was bearing North? The vessel is heading between
E.N.B. and almost South.
C Bed light bearing North? The vessel is heading between W.N.W.
and almost South.
When the vessel's head turns to starboard from position A the green
light is shut out and the observer will see only her red light until
she has swung through 10 points, that is, when she is heading
W.N.W., then it will disappear as the observer will then be 2
points abaft her beam.
2 A. Both side-lights bearing E.N.E.? The vessel is heading W.S.W.
B. Green light bearing E.N.E.? The vessel is heading between
, S.E. and W.S.W. nearly.
(7. Bed light bearing E.N.E.? The vessel is heading between Nortb.
and W.S.W. nearly,
& A. Both side-lights bearing SJL? The vessel is heading HT.W.
Turn the book round and look outwards from the centre of the
compass towards the light.
B. Green light bearing S.E.? She is heading between S.S.W. and
N.W. nearly.
C. Bed light bearing S.E,? She is heading between E.N.E. and
N.W.