AZIMUTH celest.doc

AZIMUTHS

Azimuth:- the bearing of a celestial body from an observer.

P = POLE.                 Z = ZENITH.              X = BODY.                                                                                                                                                         

                                                                                                                                                                                                                                                                                        ZP = 000°T                                                                                                                                                          PZ = 90° - LAT                                                                                                                                            PX = 90° - DEC (Polar Distance)                                                                                                                P = 360° - LHA                                                                                                                                            PZX = AZIMUTH = TRUE BRG                                                                                                                                                                                                                                                                                        ZP = 180°T

                                                                                                                PZ = 90° + LAT                                                                                                                                            PX = 90° - DEC (Polar Distance)

                                                                                                                P = LHA

                                                                                                                PZX = AZIMUTH

                                                                                                                TRUE BRG = 180° + AZIMUTH

                                                                                                                P =  LHA                                                                                                                                                          PZX = AZIMUTH 

                                                                                                                TRUE BRG = 360° - AZIMUTH

                                                                                                                P = 360° - LHA

                                                                                                                PZX = AZIMUTH 

                                                                                                                TRUE BRG = 180° - AZIMUTH                                                                                                                                                                                     
The Azimuth is calculated using A, B, C Tables or by calculator.

As can be seen from the diagrams the Azimuth is a function of:

·         Latitude,

·         Declination,

·         LHA.

A =  Tan Lat                            Named opposite to Lat except when Hour Angle between 90° and 270°

       Tan LHA

B = Tan Dec                            Always named same as Declination.

       Sin LHA

C = A ± B                            + if A and B are the same names.

                                          -  if A and B are different names.

                                          C is named the same as the greater component.

Tan Azimuth =           1             

                                C x Cos Lat

Azimuth is named by C and LHA                 LHA 0° to 180° Body is to the West of the observer

                                                                         LHA 180° to 360° Body is to the East of the observer

EXAMPLE 1

If the LHA of a Body = 285°, Observer's Lat = 36°N, Body Dec'n = 15°S. Find the True Bearing of the Body.

EXAMPLE 2

If the LHA of a Body = 48° 15', Observer's Lat = 44° 30'S, Body Dec'n = 23° 20'S. Find the True Bearing of the Body.

EXAMPLE 3

An observer obtains a compass bearing of the sun 110°C at approx 1000 hrs on 17th Dec 95. D.R. Lat 14° 23'S Long 93° 15'W. The Chronometer showed 03:50:23, Error 1m 17s slow. V/l keeping GMT - 6 hours. Calculate the Compass Error.

EXAMPLE 4

Towards the end of the 0000 hrs - 0400 hrs watch on 28th May 1995 an observer,

D.R. 10° 30'S 82° 30'E, obtained bearings of Venus  077°G and star Nunki 235½°G. Chronometer showed 10h 54m 33s, Error 1m 11s fast. Find the Gyro Error.