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INDIANA UNIVERSITY STUDIES 



Observing List. The observing list is tabulated below, with the 

 magnitude, right ascension, declination, and dates of maximum 

 displacement. 



Stars. 



Mag. 



a 



d 



First 

 Observation. 



Observation. 



70 Ophiuchi 



4.1 



18h Im 



2° 31' 



1906, Sept. 21 



1907, Mar. 21 



^ Lyrae 



4.2 



18 41 



37 30 



1906, Sept. 21 



1907, Mar. 21 



^ Geminorum .... 



3.8 



6 58 



20 43 



1906, Oct. 8 



1907, Apr. 4 



^Canis Minoris. . 



4.6 



7 22 



9 8 



1906, Oct. 14 



1907, Apr. 11 



^ Equulei 



4.6 



21 10 



9 36 



1906, Nov. 17 



1907, May 16 



61 Cygni......... 



5.5 



21 2 



38 15 



1906, Nov. 29 



1907, May 28 



>7 Pegasi 



3.0 



22 38 



29 42 



1906, Dec. 18 



1907, June 17 



(X Andromedae . . . 



2.3 



0 3 



28 33 



1907, Jan. 4 



1907, July 6 



These stars were selected so as to make it possible to observe 

 two or three on a west hour angle in the evening, and two or three 

 on an east hour angle in the morning. Unfavorable weather so 

 interfered with the observing that the number of observations is 

 very limited. A great many more stars were observed on the first 

 maximum than on the second, because the weather made it im- 

 possible to measure them on the second maximum. 



Method of Reduction. The method used in these reductions is 

 that of Bessel as developed in Chauvenet. The order in which the 

 development is given is as follows: (1) Development of the parallax 

 factor. (2) Development of the effect of proper motion and de- 

 rivation of the conditional equations. (3) Computation of the 

 auxiliaries m and M in the parallax factor. (4) Effect of differential 

 refraction. (5) Computation of T and q. (6) Investigation of 

 temperature correction for screw. (7) Effect of aberration. 



The Parallax Factor. The parallax factor As = prm cos (o - M), 

 where p = annual parallax, r = radius vector of earth, m, M = auxili- 

 aries, and 0 = longitude of the sun, is derived in Chauvenet I, p. 694. 

 To compute the auxiharies m and M use was made of Table III in 

 Sir David Gill's work on stellar parallax. ^ This gives the log /, 

 log g, F, and G for each ten minutes of right ascension and for every 

 5 degrees in declination. This table is computed for stars in the 

 southern hemisphere, but it can be used for stars in the northern 

 hemisphere by adding 12 hours to the right ascension and taking 

 log/, log g, F, and G with negative signs. 



2 Annals of the Royal Observatory, Cape of Good Hope, Vol. VIII, Pt. II. 



