AZIMUTHS 45 



wich apparent time {G.A.T.). To this G. A. T. apply the observer's 

 longitude, converted to time (subtract if observer's longitude is west 

 of Greenwich and add if observer's longitude is east of Greenwich), 

 and the result will be L. A. T. If operating under War Time or 

 Daylight Saving Tivie^ conversion should first be made to zone time 

 before any other conversions are made. 



64. Sample time calculation.— Calculate the L. A. T. for 0900.0 

 zone time on September 29, 1944. Assumed position is Norfolk, Va.. 

 U. S. A., latitude 37°00' N., longitude 76° 15' W. ( + 5 zone) . Further 

 assuming that the watch is correctly set on zone time at Norfolk, de- 

 termine the error of the watch on L. A. T. 



h m s 



Zone time (watch time) 09 00 00 Sept. 29, 1944. 



Zone description ( + ) 5 00 00 (+5 zone). 



G. C. T 14 00 00 Sept. 29, 1944. 



Eq. T ( + ) 9 42.4 (pp. 30, 1944 2V^aMiica« 



Almanac). 



G. A. T 14 09 42.4 



Observer's longitude ( — ) 5 05 00 (Longitude 76"15' 



W.). 



L. A. T 09 04 42.4 



Watch time 09 00 00 



Error of watch on L. A. T ( + ) 00 04 42.4 



Thus on September 29, 1944, 0900.0 zone time corresponds to 0904.7 

 L. A. T. 



65. When preparing and using a table or cwr-ve of azim/iiths^ as dis- 

 cussed in article 70, it must be remembered that the diflPerence be- 

 tween zone time and L. A. T, will differ slightly for each hour of 

 the day in a given locality because the Eq. T. is constantly changing. 

 However, a study of the Nautical Almanac will reveal that the hourly 

 difference in the Eq. T. is so slight as to be negligible over a period of 

 several hours. Thus, if it is desired to use azimuths of the sun from 

 0700 to 1100 zone time, the middle time of that period is selected and 

 the error of the watch on L. A. T. is calculated. If at the beginning 

 of the period, the equivalent L. A, T. is set on a well regulated watch, 

 it may then be used to obtain L. A. T. for the entire period without 

 appreciable error. 



66. Use of azimuth tables. — The following arguments are avail- 

 able for solution of the astronomical triangle : 



(1) Meridian angle, t. 



(2) Declination, d. 



(3) Latitude, L. 



