EXERCISE 37- LONGITUDE BY CHRONOMETER STAR (Numerical Solution)

We know that :

q1p1

P = 55˚ 00.8’

dia 1

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

LHA          = 055˚ 00.8’
GHA         = 162˚ 18.5’
Long. W  = 107˚ 17.7’

Obs. Long. = 107˚ 17.7’ W

q1p2

Azimuth = N 81.5˚ W

T Az          = 278.5˚ (T)

Hence ,LOP  = ( TAz  ±  90 )
=  008.5˚ – 188.5˚

  1. On 22nd Sept 2008, PM at ship in DR 60˚10’N 092˚ 27’ E, the sextant altitude of the star ARCTURUS was 25˚ 01.0’ when the chron (error 05m 01s SLOW) showed 00h 46m 31s. If IE was 0.2’ on the arc & HE was 17m, find the direction of the LOP and the longitude where it cuts the DR latitude.
 q2p1
GMT     22 Sept 12h  51m  32s

GHA Ȣ(30d 12h)      180˚  44.2’                                           Dec         N  19˚  08.3’
Incr. (51m 32s)       012˚  54.6’                                             Lat            60˚  10’ N
GHA Ȣ                     193˚  38.8’
SHA *                (+) 145˚  59.2’
GHA *                     339˚  38.0’

Sext Alt                         25˚ 01.0’
IE (ON)                            (-) 00.2’
Observed Alt               25˚ 00.8’
Dip (HE 17m)                 (-) 07.3’
App Alt                         24˚ 53.5’
T Corrn.                          (-)02.1’
T Alt                            24˚ 51.4’

dia 3

We know that :

q2p2

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