EXERCISE 34 – AZIMUTH STAR (Numerical Solution)

1. On 06^th March 2008, AM at ship in DR 24˚ 12’ S 083˚ 46’ E, the azimuth of the star ALTAIR was 078˚(C) when chron showed 10h 38m 40s. If the chron error was 03m 24s FAST and variation was 3˚W, find the deviation for the ship’s head.

GMT     05 March 22h  35m  16s

GHA Ȣ(05d 22h)            134˚  01.0’                                           Dec         N  08˚  53.2’
Incr. (35m 16s)             008˚  50.4’
GHAȢ                              142˚  51.4’
SHA  *                          (+)062˚  12.4’
GHA *                            205˚  03.8’
Long (E)                     (+)083˚  46.0’
LHA  *                            288˚  49.8’

NOTE:

Working is very similar to that of azimuth- Sun, except that GHA Ȣ and SHA * have been used, which can be taken from the nautical almanac.

P = (360˚ – LHA)
= (360˚ – 288˚ 49.8’)
= 71˚  10.2’

We know that :

Azimuth = N 73.8˚ E

T Az          = 073.8˚ (T)
C Az          = 078.0˚ (C)
Error         = 4.2˚ W
Variation  = 3.0˚ W
Deviation = 1.2˚ W

2. On 30^th Nov 2008, PM at ship in DR 48˚ 57’ N 173˚ 18’ W, the azimuth of the star VEGA was 296˚(C) when the GPS clock showed 07h 39m 22s. If variation was 1˚E, calculate the deviation of the compass.

                                  d       h      m      s
GMT                        01    07      39    22
LIT (W)                    (-)     11      33    12
LMT                         30    20    06     10