| G.S.T. | 6h 07m 18s |
| (74° W) | - 4 56 00 |
| ——————— | |
| L.S.T. | 1h 11m 18s |
Now these are not a collection of abstruse formulas that you are learning just for the sake of practice. They are used every clear night on board ship, or should be, and are just as vital to know as time by the sun.
Suppose you are at sea in Lo. 70° W and your CT is October 20th 6h 4m 30s A.M., CC 2m 30s fast. You wish to get the R.A. of your M, i.e., the L.S.T. How would you go about it? The first thing to do would be to get your G.M.T. It is CT—CC.
| 20d 06h 04m 30s A.M. | |
| - 12 | |
| ————————— | |
| CT | 19d 18h 04m 30s |
| CC | - 02 30 |
| ————————— | |
| G.M.T. | 19d 18h 02m 00s |
| Then get your G.S.T. | |
| Oct. | 19d 18h 02m 00s |
 .R.A. | 13 47 38.5 |
 .C.P. | 2 57.7 |
| ————————— | |
| 19d 31h 52m 36.2s | |
| - 24 | |
| ————————— | |
| G.S.T. | 19d 7h 52m 36.2s |
| Then get your L.S.T. | |
| G.S.T. | 7h 52m 36.2s |
| W.Lo ( - ) | 4 40 |
| ————————— | |
| L.S.T. | 3h 12m 36.2s |
The last fact to know at this time about the Almanac is found on pages 94-95. Here is given a list of the brighter stars with their positions respectively in the heavens, i.e., their celestial longitude or R.A. on page 94 and their celestial latitude or declination on page 95. These stars have very little apparent motion. They are practically fixed. Hence, their position in the heavens is almost the same from January to December though, of course, their position with relation to you is constantly changing, since you on the earth are constantly moving.
The relationship between these various kinds of time is clearly expressed by the following diagram, which put in your Note Book:
Assign for reading in Bowditch, Articles 294-295-296-297-299-300-301-302-303-304-305-306-307.
If any time is left, have the class work out such examples as these:
1. G.M.T. June 20th, 1919, 5h 14m 39s. In Lo. 68° 49' W. Required L.S.T., G.S.T., L.M.T., L.A.T.