AZIMUTU OBSERVATIONS. 39 



An example of reduction is as follows: 



AZIMUTH OBSERVATIONS. 



Example of reduction. 



[Station: West base; December 27, 1888. Observer, S. S. G. Latitude=34 45 20.8 Longitude 92 13 31.5.] 



h. in. « 



Time of observation =Tw = 1] 00 18 



Correction; ninetieth meridian time to 92°.215 = — 8 51 



Watch slow; ninetieth meridian time + 02 



When observations for azimuth are to be made at elongation, it is nec- 

 essary to know the mean time of elongation. This is computed by the 

 following method: the hour angle at elongation is obtained from the follow- 

 ing equation: 



cos t e —tan q> cot S. 



The hour angle plus the right ascension of the star gives the sidereal 

 time of its western elongation, which, reduced to mean time, gives the local 

 mean time in question. 



The azimuth of a pole star at elongation is determined by the use of 



the following equation : 



sin A — sec (p cos S. 



