STARS IN COMA BERENICES. 445 



gular coordinates. I have used those of Professor Jacoby^ 

 which were deduced by him from Dr. Rambaut's formulae 

 pubhshed in the AstronoiiiiscJic NacJiricJitcn, No. 3125. Let 



(D = the latitude of the place, + 40° 43' 50'' in my case ; 



d — «o = ^^^^ hour angle of the center of the plate, d being the 



" Sidereal Time " from Taele I, and a„ the right as- 



' U «^ 



cension of star 14, roughly corrected to the date of 

 observ^ation ; 



0^ = the declination of the center, Star 14 ; 



/9 = the constant of refraction computed for the center 

 with the argument "True Zenith Distance," Cq, and 

 multiplied by ||- to allow for the increased refran- 

 gibility of the actinic rays" ; so that ^ ^ k' . ||- 

 (Chauvenet, Astr., Vol. I, §§ 119, 120). 

 Now compute the quantities 



tan iV= cos [d — «„) cot 

 G = cot (^0 + A') 

 Zr= tan {Q — Gg) sin iVcosec {S^A^ N) 



then will 



tan2 ^p = C^ -]- H"^ ' (Chauvenet, Vol. I, equ. (20) ) 



M^:=z[3{l +^2) sin J// 



Nx = P[G — tan 6^) I/sec S^ sin l^-' 

 My = l3{G + tan Sq) H cos 6^ sin \'f 

 iVj, = /3(i 4- (?2) sin \" 

 and the refraction corrections will be 



Correction to X sec Jj = Mj^ ■ X sec 6^ -[- N^ ■ Y 

 Correction to F = My - X sec S^ -\- Ny ■ Y 



where evidently the coefficients of XsecOj, and Fin the second 

 members are constant for each plate but vary for different 

 plates. 



1 Astronomical Journal, No. 387. 



2 Cf. Scheiner and Rambaut, Astrom. Nachrichten, No. 3255. 



(105) 



