Examples

Ex26-1 A celestial body is observed at a station (latitude 36° 04' 00" N and longitude 94° 10' 08" N). The UTI at the instant of observation was (15h 16m 41s.57).The GHA at 0hr (UT1) was found to be 177° 04 ' 44".1 on the day of observation and 177° 08' 06".3 on the next day. The declination of the selected body at 0hr (UT1) was + 6° 15' 05".9 S and + 5° 5' 54".7 S on the day of observation and next day respectively. Determine the azimuth of the celestial body.

Figure Example 26.1

Soluton : Given, GHA at 0hr = 177° 04 ' 44".1

GHA at 24hr = 177° 08' 06".3

Instant of observation of the celestial body = 15h 16m 41s.57

Using linear interpolation method,

the GHA at the instant of observaton =

= 177° 04' 44".1 + (177° 08' 06".3 - 177° 04' 44".1 + 360°) x

= 406.28788° - 360° = 46.28788°

Thus,

Local Hour angle at the instant of observation, LHA = GHA - Wl (The station is at west to Greenwich)

= (46.28788° - 94° 10' 08") = - 47.88101° = -47.88101° + 360°

= 312.11899°

Declination (d)of the celestial body at the instant of observation (Implementing linear interpolation)

d = - 6° 15' 05".9 + ( - 5° 51' 54".7 + 6° 15' 05".9) x = - 6.00563°

Now, using the relation (Equation 26.3), azimuth of the celestial body

Z =

=

= - 57.10487745°

Since, LHA is between 180° and 360° and A is negative (Figure Ex 26.1), thus

Azimuth of the body, A = Z + 180° = - 57.10487745° + 180°

= 122.8951226° = 122° 53' 42 ".44

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