Stars liable to Occultation. 157 



9 ifX, .»)^8. xAur.»yn, , <r^^, jjatfj?, , cram AOph. T /, 



6' if X, , »J^ 8 , «Aur. »« n , 725, <rSl&y riocnjl, , <r«1tl, ^t ^ , ly^Y? , , 

 3 «X»,*>^8> xAur.iyn, y2S, o-J|^i3, an|^, ttTIX, ^ain,» ^t/, 



«X»,»)i38, xAur.ivn, y2S, crj^jj, att^, wTtl, <?-ani» ^t /, 



4. Explanation of the Second Table. 



The method of computing the solar nutation, to which these 

 tables are adapted, is neither altogether new, nor always the 

 most convenient : but for the places of single stars, in cases 

 like the present, it possesses some advantages, and may there- 

 fore deserve to be further explained and demonstrated, notwith- 

 standing the trifling magnitude of the correction. • 



The formula employed by Bessel for the right ascension is — 

 ta ^ ( ",3982 sin a sin 2 © + ",434 cos a cos 2 O) — ' -9173 sin 

 2 0; and for the declination, — ",3982 cos a sin 2 © + ",434 

 sin a cos 2 O . But it is known, that in general a sin a; + b cos 



a:= -/ (a* + ^') sin {x + ang ta— J . (M. E. §.216) : and for the 



a/ f 



right ascension we have azz — ta ^ .3982 sin a — .9173, and 

 b zz. — ta 5* .434 cos a, and ang ta — zz ang cot — - iz ang cot 



u 



/.3982 .9173 . \ ^,„r , 



( — -r-, ta a 4- — -— • cot ^ sec. « = ang cot .9175 (ta a -f 



\ .434 .434 J 



2.3036 cot ^ sec a) : and this angle being found, the factor 



V (a* + i* ) will be obviously equal to its cosecant multiplied 



by by or by — .434 ta ^ cos a. In the same manner we obtain 



for the declination a := — .3982 cos a, and 6 n: + .434 sin «, 



and ang ta — zi ang ta — -^-— - ta a =: ang ta (—1.0900 ta a) : 

 a .oyo<i 



the cosecant being again multiplied by 6 z= .434 sin «, for 



the factor. 



Taking, for an example, the first star of the table, « X, we 



have a = 0" 53M 36^,5 = 13^ 24' and ^z= + 6° 55' (11") 



whence nat. ta « = .2382, log ta « = 9.3770 log sec «= .0120 



