a spot
on the earth 5h 16m 32s to travel until it reaches the meridian of the
star in question.

Roughly speaking then, just as Greenwich Apparent Time means the
distance East or West the Greenwich meridian is from the sun and Local
Apparent Time means the distance East or West your ship is from the sun,
so R.A.M.G. means the distance in time the Meridian of Greenwich is from
the First Point of Aries, measured eastward in a circle. And this
distance is the same as Greenwich Sidereal Time, i.e., Sidereal Time at
Greenwich or the distance in time the meridian of Greenwich is from the
First Point of Aries.

Now, what is the star time that corresponds to local time? It is called
the Right Ascension of the Meridian, which means the R. A. of the
meridian which intersects your zenith. Just as L.A.T. is the distance in
time your meridian is from the sun, so Local Sidereal Time is the R. A.
of your meridian, i.e., the distance in time your meridian is from the
First Point of Aries. Put in your Note-Book:

G.S.T. and R.A.M.G. are one and the same thing.
L.S.T. and R.A.M. are one and the same thing.
G.M.T. + (.).R.A. + (+).C.P. = G.S.T. (R.A.M.G.) If the result is
more than 24 hours, subtract 24 hours.
G.S.T. - (.).R.A. - (+).C.P. = G.M.T.
G.S.T. - W.Lo. = L.S.T.
+ E.Lo.
L.S.T. + W.Lo. = G.S.T.
- E.Lo.

I can explain all these formulas very easily by the following
illustration which put in your Note-Book: (Note to Instructor: If
possible have copies of this illustration mimeographed and distributed
to each student.)

[Illustration: FIRST POINT OF ARIES.]

There is one term I have used which does not appear in the illustration.
It is the Earth's Central Progress ((+).C.P.). The astronomical day
based on the sun, is 24 hours long, as said before. The sidereal day,
however, is only 23h 56m 04s long. This is due to the fact that whereas
the earth is moving in its ecliptic track around the sun while revolving
on its own axis, the First Point of Aries is a fixed point and hence
never moves. The correction, then, for the difference in the length of
time between a sidereal day and a mean solar day is called the Earth's
Central Progress and, of course, has to be figured for all amounts of
time after mean noon at Greenwich, since the Sun's Right Ascension
tables in the Nautical Almanac are based on time at mean noon at
Greenwich.

Now you have a formula for practi