EXERCISE 37- LONGITUDE BY CHRONOMETER STAR (Numerical Solution)

 

P     = 46˚ 30.0’

Since, sight is before mer. Pass. ,

So LHA = (360 – P)

LHA          = 313˚ 30.0’
GHA         = 142˚ 36.5’
Long. E    = 172˚ 53.5’

Obs. Long. = 172˚ 53.5’ E

Azimuth = N 79.8˚ E

T Az          = 079.8˚ (T)

LOP = 169.8˚ – 349.8˚

4. On 30^thApril 2008, PM at ship in DR 34˚ 18’S 040˚ 20’W, the sextant altitude of the star SIRIUS was 57˚ 51.9’ at 08h 53m 03schron time. If CE was 01m 40s FAST, IE was 1.2’ on the arc & HE was 21m, find the direction of the LOP and the longitude where it cuts the DR latitude.

GMT     30 April 20h  51m  23s

GHA Ȣ(30d 20h)          147˚  06.9’                                           Dec         S  16˚  43.7’
Incr. (51m 23s)            012˚  52.9’                                           Lat            34˚  18’ S
GHA Ȣ                           172˚  00.7’
SHA *                    (+) 258˚  37.3’
GHA *                         070˚  38.0’

Sext Alt                           57˚ 51.9’
IE (ON)                             (-) 01.2’
Observed Alt                 57˚ 50.7’
Dip (HE 21m)                  (-) 08.1’
App Alt                           57˚ 42.6’
T Corrn.                           (-)00.6’
T Alt                              57˚ 42.0’

We know that:

P = 30˚ 18.0’

Since, sight is AFTER mer. Pass. ,
So , LHA = P

LHA          = 030˚ 18.0’
GHA         = 070˚ 38.0’
Long. W   = 040˚ 20.0’