STARS - To find the GHA, DEC, and LHA of a star is a little more,work than the sun or planet. Since stars hardly change their position on the celestial sphere in a year. (this change is very small, less than 0.5'). So, it is impracticable to tabulate the GHA and DEC of the stars like the planet, sun and moon for every hour of GMT. Thus the Nautical Almanac tabulates the GHA Aries. From Aries then each star's SHA is added, GHA star = SHA star + GHA Aries. In addition, there is no "d" correction for the star's declination, See problem 3 for explanations.
Problem 3:
On the 15 October 1981, your vessel's 0325 ZT DR position is LAT 26"51.0'N, LONG 138°117.0, you take a celestial sight of the star Canopus. The chronometer time of the sight is OOh 25m 36s. The chronometer error is OOm 20s slow. Compute the GHA, Dec., and LHA of Canopus
BODY CANOPUS
DATE 15 Oct. 1981
DR LAT 26-51.0 N
DRLONG 138-17.0 W
Hs
IE
Hs
Dip
Ha
ALT CORR
Ho
ZT 15th 0325
ZD +9
GMT 15th 1225
CT 00h 25m 36s
CE + 00m 20s slow
CCT 15th 12h 25m 56s
GHA (Aries) 203-55.8
M&S (Aries) 6-30.1
SHA (Star) 264-06.7
V ---------
GHA (Star) 114-34.3
DR LONG + 138-17.0 W
LHA 336-15.6
TAB DEC ----------
d corr ----------
DEC S 52-40.9
STEP 1
Using GMT, and Greenwich date of observation, enter Nautical Almanac and record tabulated hourly value of GHA (Aries).
STEP 2
On the same daily page find the SHA and DEC. of Canopus and enter them in your format. Since, there is no "d" correction, the DEC is entered on the bottom declination line.
STEP 3
Turn to the yellow pages of the Nautical ~lm?~, and find the "25 minute page," enter with "56-seconds." Then under the "ARIES" column find the increase in the GHA (Aries) since the last tabulated (hourly) value, hence 6" 30.1.' This is your M&S correction and enter this in your format.
STEP 4
Add the GHA Aries, M&S, and SHA to get the GHA of the STAR.
STEP 5
Bring down your DR longitude and enter it in your form. The rule is:
LHA = GHA + EAST LONGITUDE - LHA = GHA - WEST LONGITUDE
So, we subtract our DR longitude to get the LHA of Canopus.
