Assign for Night Work reading also, the following Articles in Bowditch: 344 and 223.
THURSDAY LECTURE
Azimuths Of The Sun
This is a peculiar word to spell and pronounce but its definition is really very simple. Put in your Note-Book:
The azimuth of a heavenly body is the angle at the zenith of the observer formed by the observer's meridian and a line drawn to the center of the body observed. Azimuths are named from the latitude in and toward the E in the A.M. and from the latitude in and toward the W in the P.M.
All this definition means is that, no matter where you are in N latitude, for instance, if you face N, the azimuth of the sun will be the true bearing of the sun from you. The same holds true for moon, star or planet, but in this lecture we will say nothing of the star azimuths for, in some other respects, they are found somewhat differently from the sun azimuths. Put this in your Note-Book:
To find an azimuth of the sun: Note the time of taking the azimuth by chronometer. Apply chronometer correction, if any, to get the G.M.T. Convert G.M.T. into G.A.T. by applying the equation of time. Convert G.A.T. into L.A.T. by applying the longitude in time. The result is L.A.T. or S.H.A. With the correct L.A.T., latitude and declination, enter the azimuth tables to get the sun's true bearing, i.e., its azimuth. Example:
March 15th, 1919. CT 10h 4m 32s. D.R. latitude 40° 10' N, longitude 74° W. Find the TZ.
| G.M.T. | 10h 04m 32s |
| Eq. T. | - 09 10 |
| —————— | |
| G.A.T. | 9h 55m 22s |
| —————— | |
| G.A.T. | 9h 55m 22s |
| Lo. in T. | 4 56 00 (W - ) |
| —————— | |
| L.A.T. | 4h 59m 22s |
| Latitude and Declination opp. name. | |
| TZ = N 101° 30'W | |
| —————— | |