EXERCISE 29 — RISING/SETTING AZIMUTH -SUN (Numerical Solution)

  1. On 2nd Sept 2008, in DR 40˚ 28’N 064˚ 20’E, the rising sun bore 090˚(C). If variation was 5˚ W, find the deviation of the compass.

LMT Sunrise         = 2d  05h  28m  00s
LIT (E)                  = (-)   04h  17m   20s
GMT Sunrise      =  2d   01h   10m  40s
Dec (sun ) 2d 01h  10m  40s
=  07˚  50.3’  N

As we know that:
LMT of Sunrise or Sunset are taken from the nautical almanac and needs only be interpolated and taken in whole minutes of time. If the time ofobservation is given in the problem, then given time should be used for calculation. It is necessary to remove the ambiquity of chron time.

We know that:

e29q1p1

NOTE:

NAMING OF AMPLITUDE: The prefix of True Amplitude is E if the body is rising and W if the body is setting. The suffix is same as that of the declination.

T Az          = 079.7˚ (T)
C Az          = 090.0˚  (C)
Error         = 10.3˚ W
Variation  = 05˚ W
Deviation = 5.3 W

  1. On 1st May 2008, in DR 30˚ 06’N 179 ˚ 45’W, the setting sun bore 285˚(C). If variation was 2˚W, find the deviation for the ship’s head.

LMT Sunrise    = 1d   18h    38m  00s
LIT (W)             = (+)   11h    59m  00s
GMT Sunset    = 2d    06h   37m  00s 

As we know that:
LMT of Sunrise or Sunset are taken from the nautical almanac and needs only be interpolated and taken in whole minutes of time. If the time ofobservation is given in the problem, then given time should be used for calculation. It is necessary to remove the ambiquity of chron time.

Dec sun  2d  06h                = N 15˚  30.1’
d (+0.7)                                =    +       00.4’
Dec 2d  06h  37m  00s      = N 15˚  30.5’

We know that :

e29q2p1

NOTE:

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