Stars liable to Occult atioti, 159 



5. Computation of the Elements for an Almanac. 



i. With the longitude of the moon's node for the beginning 

 and end of each lunation, enter the first table, and put down 

 all the stars liable to occultation at either place of the node, 

 for further examination. 



Example. In February, 1822, the node recedes from 10' 

 26° 5' to 10* 24^ 49', and the stars liable to occultation are, 

 uf/3 B, xU^a^vSl, ittR, TTcraTttl, A Ophiuchi, <7-»f//,SYJ. 



ii. Find, by inspection of the moon's right ascension, the day 

 on which the conjunction with each of these stars will take place, 

 and compute the corrections from the sun's longitude and the 

 place of tlie node on that day. 



Example. Taking v <J^, of which the AR. in space is 

 171° 56' f we find that the occultation will happen on the 8th, 

 a little before midnight, when the sun's longitude is 10" 19° 44', 

 and that of the ^ 10* 25° 41'. The time from 1st Jan. 1820 

 is 2 -^^-^ years, whence the precession is + 6%47 and + 4r',9. 

 For the aberration, we add 3' 9° 0' and 3* 0° 44' to the 0*s 

 longitude, making 13» 28° 44' and 13* 20° 28', and the loga- 

 rithmic sine of + 58° 44' being 9.9318, this being added to 

 .0935 gives .0253, or 4- P,06, for the correction in AR. ; and in 

 the same manner L. sin 50° 28', or 9.8872, added to .9058, gives 

 .7930 or + 6",2 for the correction of the N. P. D. The ar- 

 guments for the solar nutation are 5" 29° 56', and 6' 8° 47' 

 to which we add 2% 9° 28', making 27" 9° 24', or 3" 9° 24', the 

 sine of which is the cosine of 9° 24', and 9.9941 -f 8.785= 

 8.779, giving + ',06 for the AR. ; and 27" 18° 15' gives us 

 9.978 + 9.62 = 9.60, and the correction for the N.P. D. is ",4. 

 The lunar nutation is found from the arguments 5' 29° 50' and 

 6' 11° 13', making with 10' 25° 41', 16" 25° 31' and 17* 6° 54', 

 of which the logarithmic sines are 9.753 and 9,594, to be 

 added to .0426 and .8602, making 9.797 and .454, and giving 

 -H ',62 and + 2",8 for the lunar nutations. The result of the 

 whole is, 



