ON MAPPING THE SURFACE OF THE MOON. 235 



Latitude 51° 3' 0" N., longitude O'^ 45" 40' E. of Paris Observatory, from 



whence o / /< - 



a>'= 50 51 53 



log p= 9-9991353 

 log (p sin 0')= 9-8888055 

 Iog(pcos0')=9-79927O3 

 J& = 34 35 45 

 Parallax in Right Ascension and Declitiatlon. 

 The next step is to obtain the apparent right ascension and declination of 

 the moon. 



Also p'=JS".P.D. of moon's apparent centre =90 + S', S'N,— ^'8,+ 



A= inclination of iiop'= 90°— £3 ' + a', or 



=270°+ £3 '-a'. 

 Let a! = the moon's apparent right ascension ; 

 1'= the moon's apparent declination; 

 then for a' we have pcos0'sin,r . , .. 



tan (a'-a)= tan a"= .; 22ii__ ,, ^^^^l^cos (a-^)=«. 



^ ^ 1— pcos0sm7r / Q. cos 6 



— -! i- — — cos(a— & 



cos a 



a = 50 44 54 

 ^ = 34 35 45 



logo cos d,' 9-79927 logP""'^ '""^ 8-06829 



cos 2 



(a-d)= 16 9 9 



9-79927 lo| 



log sin ,r 8-23308 logcos(a-^) 9-98251 



ar. CO. log cos S 0-03594 sum=logji 8-05080 



sum = 8-06829 n 0-01124 



log sin (a-^) 9-44434 (l-«) 0-98876 



ar. CO. log(l— «) 0-00491 



sum = log tan a" 7-51754 



a. 



I II 



+ 11 19 



ec 50 44 54 



sum = a 50 56 13 



For h' we have 



^^j^g_psin£8W 



tana'= ^_22ii xcos(a'-a), fl^^^^=.J^, 



^_pcos^^^m. cosS 



cos g ^ ^ 



log p sin 0' ,9-88880 log (tan a— ^-) 9-61266 



log sin TT 8-23308 ar.co. log(l— n) 0-00491 



