62 



Rutherfurd Photographic Measure?; of 





Scale Variation 



Plate. 



Factor x 10 3 . 



I 



+ .1948 



2 



+ -2275 



3 



+ .1666 



4 



— .0027 



5 



+ -0439 



6 



+ -0894 



7 



+ .0928 



8 



— .1272 



9 



— .0442 



IO 



— .0408 



ii 



— .0714 



12 



— .0593 



*3 



— .0129 



15 



— .1047 



16 



— .0670 



17 



— .0714 



18 



— -0537 



19 



— .0326 



20 



— .1241 



11. The measures of distance are next to be corrected for the 

 proper motion of the central star. For this purpose let : 



t = date of the plate. 



T=t 1873.O 



p = annual motion on great circle 

 ;t = position-angle of that great circle 



S 1 ^cos(x—p) 



8 2= — ^ sin2 (X—p) 



P 1 = T P 



The correction for proper motion, additive to observed distances, 



will then be : 



Aa = 8 1 P 1 -\-8 2 P 2 



I have adopted Auwers's values of 



s , „ 



P = + 0-3444, H- = + 3-230, 



as given in the Fundamental Catalog. Corresponding to these 



are: 



,1 a o , 



p = 5.1904 = 0.18528, x == 51 30 56 



The values of p used in the above formulae were the means after 

 correction for " zero " and refraction, as explained in paragraph 

 7 ; and the values of s were after correction for scale variation. 



