DEPARTMENT OF MERIDIAN ASTROMETRY. 



195 



REDUCTIONS OF OBSERVATIONS. 



When the reduction of the Albany zenith-distance observations, under the 

 supervision of Mr. Roy, was suspended in March, pending the results to be 

 derived from the study of differential refraction, the computations were in an 

 advanced stage. Many of the least-square solutions for the final equator-point 

 and refraction correction had been made and the normal equations for the 

 remainder were ready for solution. The critical examination to determine 

 which series needed a revision of the rate in the equator-point as given by the 

 nadirs was well started. 



In the preliminary reductions it was assumed that the minor variations of 

 the refraction constant could be ignored, but it developed that there were 

 marked changes, sometimes within a short period of time. The tremendous 

 changes in the refraction constant, under weather conditions outwardly 

 fairly uniform, are illustrated by 3 days in May 1916. 



An assumption that the refraction constant has a uniform daily variation 

 or that it remains constant for many hours at a time would do violence to the 

 observations. 



The San Luis zenith-distance observations are completely reduced. The 

 means in declination have been formed as far as 7 hours 43 minutes, the forma- 

 tion being suspended in March. The secular variations have been checked in 

 both coordinates. 



An attempt was made to determine the correction to the refraction constant 

 from the San Luis circumpolar observations. A correction to the latitude of 

 — 0''51 was obtained, and the correction to the refraction constant was 

 +0''31. When the material was collected according to groups of stars in each 

 degree great anomalies appeared. The results show the necessity of modifying 

 the Pulkova refraction tables to fit a particular station when attempting 

 fundamental work. 



THE PROPER-MOTIONS OF 154 RED STARS. 



Due to their faintness, coupled in general with magnitude variation, the red 

 stars, Classes Md, N, and R, have been neglected by meridian observers and 

 proper-motions of but a few of them have been available to students of 

 stellar motions. In view of their peculiar relations to the sequence of stellar 

 evolution, it is important that as much information as we can secure with 

 regard to their motions be made available. In the Astronomical Journal, No. 

 796, Dr. Wilson published proper-motions of 154 of these stars. From an 

 analysis of the data given therein the following conclusions were reached : 



1. The proper-motions of the Class M stars are in general small, their veloci- 

 ties in the line of sight are large; apparently, therefore, their real motions are 

 large, they are very distant, and the majority of the stars of this class whose 

 proper-motions are known must be giants. 



