ASTRONOMICAL PROBLEMS. 517 
R. A. by calculation =13> 43™ 2485 
recorded in Naut. Alm.=135 43™ 248-29 
Difference= 0b O™ (8-28. 
Problem VII. Calculate the R. A. of the same star for lst January 
1820 from recorded data 1st January 1887. 
Then similarly we obtain 
angle P=64° 41’ 53’:-4= 4h 18™ 475-5 
+67 x 719 Oe 
R. A. by calculation =18"— 4h 19™ 358-67 
= 13) 40™ 248 -33 
recorded in Naut. Alm. 1820 13 40™ 268-43 
Difference= 0h O™ 95°10, 
Problem VIII. Calculate the R. A. 
and Decl. of Spica (a Virginis) for Ist 
January 1820 from data given in the 
Nautical Almanack for 1st January 1887. 
1.1.87 a Virginis 
ReA= 13h 19m 48:35) 
Decl. =10° 34’ 16”°3—S.. 
angle P=18"— 13 19™ 148-35 and N.P.D. 
=70° 11’ 24-75 ; (Pa) =100° 34’ 16-3. 
CP=297 251477 
log cos P= 9°5300700 100° 34’ 16”°3 
log tan PC= 9°7513982 Ist are 10° 49’ 26” 
log tan Ist are=19-2814682 2nd arc= 89° 44’ 507-3 
sin C=sin P = Ee 
sin Ca log cos 2nd arc= 7:°6444710 
log sin P= 9:97350786 log cos CP= 9:9399977 
log sin Pa= 9°99256574 UVR 
175844687 
19-9660736 —log cos 1st arc= 9°9922039 
— log sin a= 99999967 log cos Ca= 7°5922648 
log sin C= 9-9660769 o. Ca=89° 46’ Be iipy 
409 
te; 
286 3 
0 =180° — 67° 38" 51” Se | 
= 112° 21' 9" 27403 
— 45/403 = 45) 40-3 
angle C=111° 35’ 28’"7 on 1.1.20. 
If P’ be the position of the pole on 1.1.20, then in the triangle 
CP’a we have to find P’a, the N.P.D. of a at that date, and so get the 
Decl. required. 
