REPORT OF COMMISSION V GV—9 
If the numerator is negative, £ is between 90° and 270°. If the observed 
azimuth is between 0° and 180°, + cos t is between 270° and 360? and —cos t 
is between 180° and 270°. If the observed azimuth is between 180° and 360°, 
+ cos t is between 0° and 90° and — cos ¢ is between 90° and 180°. The sign con- 
vention is shown in the following table. 
SIGN CONVENTION OF t 
  
Az | + cos ¢ | — cos 
12^ to 18^ 
6^ to 12^ 
0? to 180? 18^ to 24^ 
180? to 360? | 0^ to 6^ 
Then 
LST = (Radio time + time zone) + GST 0" + sol.-sid. corr. — À (time) 
GCT = (Radio time + time zone) 
The date of (Radio time+time zone) 2 GCT is the argument for obtaining 
GST 0^, and is also the argument for obtaining solar to sidereal correction from 
105°. Qo" 
  
TT DECLIVNATION (8) 
  
  
  
  
  
RIGHT ASCENSION (RR) 9 
FrG. 4. Star identification. 
tables found in the American Ephemeris. À =longitude of observer and is the 
angle measured eastward in the eastern hemisphere, and westward in the western 
hemisphere, in the plane of the equator from the zero meridian passing through 
Greenwich to the meridian passing through the observer. 
2. Declination. Computation of declination is straightforward and is ob- 
tained without reference to time. 
sin à = sin » sin à + cos h cos à cos Az 
Sin à is negative when the Az is between 90° and 270° and the product cos % 
cos ¢ cos Az is greater than sin 4 sin ¢. 
Assume, now, that the celestial coordinates of the principal point have been 
determined. The celestial coordinates of the observer and the principal point 
are plotted on a star chart. The negative is positioned over the point correspond-