246 Preesepe Group; Measurement and Reduction. 



know X sec § Q in computing the correction to the declination, 

 but for this purpose we may use 52.87(1 +p + M x ) sec d • x, the 

 quantity which we have just computed and which is practically 

 equal to X sec d for this purpose. Similarly in the declination 

 we may compute at once 52.87(1 + p + N). 



Employing these coefficients for Star 7 we have : 



Right Ascension : Declination : 



a; : (Tab. V), — 14.6960 #:(Tab. V), — 19.0252 



52.87(i+2>+^)secrf -a;:— 828/ / 69 52.87(1+2/+^)^: — 1006". 62 



= — 13'48.69 =— 16 / 46 // .62 



(N x -\-r sec d )-Y: — 0.30 (M y — rsec^ )-Xsec 6 : — 0.03 



a -\-ksecd Q : i2S°oy 54 .84 ■ rf +c : +20°i3 01 .39 



«i = i27°54 / o5 // .85 6 1= = 4-i 9 °56'i4".74 



These give the projected position ; the true right ascension and 

 declination are found by adding the transformation corrections 

 from Table YI, giving : 



a = i27°54 / 7 // .34 , 6 = -\-ig° 56^14^.22, 



which are corrected for refraction, precession, nutation and aber- 

 ration, and are referred to the mean equinox of 1875.0. 



