Q-QRE — On the Ofbit of the Binary Star j3 Delphini. 539 



P DELPHINI. 



Angles and Distances, Epoch 1880-0. 



R. A., 1880, 20'' 31" 54^ 

 Decl. N., 14° 11". 

 Magnitudes, 3-5, 4* 5. 



t 



e 



r 



No. 



of 



Nights. 



Observer. 



1874-66 



l5°-6 



0"-61 



5 



Dembowski. 



1874-80 



15 -1 



-4 + 



— 



Schiaparelli. 



1875-65 



20 -1 



-54 



4 



Dembowski. 



1876-66 



25 -8 



-48 



4 



n 



1877-79 



40 -8 



-32 



4 



Burnbam. 



1878-65 



53 -7 



-24 



4 



J) 



1878-70 



59 -2 



oblong. 



1 



Dembowski. 



1880-68 



133 -6 



-26 



5 



Burnham. 



1881-50 



149 -2 



26 



5 



5) 



1882-60 



167 -5 



-26 



3 



J) 



1883-25 



183 -90 



-194 



— 



Englemann. 



1883-55 



182 -50 



. -23 



3 



Burnbam. 



1884-71 



197 -75 



-32 



— 



Englemann. 



i 



These observations were plotted on squared millimetre paper, and 

 an interpolating curve carefully drawn among them. A table was 

 then formed of interpolated epochs for position angles differing by 5°, 

 by readings from the interpolating curve. These were then corrected 

 by adjusting the second and third orders of differences so as to 

 '' smooth" the curve. The radius vector for each angle was then 

 found from the differences of epoch and angle by the formula 



r= C 1—-^, C berag assumed as 400 millimetres. The polar co- 

 ordinates, r, 6, thus found, were then converted into rectangular co- 

 ordinates by the usual formulae, x = r cos 6, y - r sin B. The results 

 thus found are shown in the following table : — 



R. I. A. PROC, SER. II., VOL. IV. — SCIENCE. 



3 A 



