EXERCISE 36 – INTERCEPT STAR (Numerical Solution)

  1. On 29th Nov 2008, AM at ship in DR 25˚ 30’S 107˚ 20’W, the sextant altitude of the star RIGEL was 35˚ 10.3’ when the GPS clock showed 11h 29m 20s. If IE was 2.8’ on the arc & HE was 12m, find the direction of the LOP and the intercept.

                                      d       h    m   s
GMT                            29    11  29  20
LIT (W)                        (-)    07  09  20
LMT                             29    04  20  00

GMT     29  Nov  11h  29m  20s

GHA Ȣ(29d 11h)              233˚  42.3’                                           Dec         S  08˚  11.4’
Incr. (29m 20s)              007˚  21.2’                                           Lat            25˚  30’ S
GHA Ȣ                                241˚  03.5’
SHA *                          (+) 281˚  15.0’
GHA *                                162˚  18.5’
Long (W)                  (-) 107˚  20.0’
LHA  *                             054˚  58.5’

P  = LHA
= 54˚  58.5’

dai 3

Cos CZD = ( Cos P × Cos Dec × Cos Lat) + ( Sin Lat × Sin Dec )
Cos CZD = ( Cos 054˚  58.5’ × Cos 08˚  11.4’ × Cos 25˚  30’  ) + ( Sin 25˚  30’  × Sin 08˚  11.4’ )
CZD = 54˚  57.9’

Sext Alt                             35˚ 10.3’
IE (ON)                             (-) 02.8’
Observed Alt                35˚ 07.5’
Dip (HE 12m)                (-) 06.1’
App Alt                          35˚ 01.4’
T Corrn.                          (-)01.4’
T Alt                              35˚ 00.0’
TZD                              55˚ 00.0’

TZD             =   55˚ 00.0’
CZD             =   54˚ 57.9’
Intercept    =   2.1’ AWAY

q3p1

Azimuth = N 81.9˚ W

T Az          = 278.1˚ (T)

LOP = 008.1˚ – 188.1˚

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