DEPARTMENT OF MERIDIAN ASTROMETRY.^ 



Benjamin Boss, Director. 



As in previous years, the work of the Department has been mainly 

 divided between computation in preparation of the observations 

 taken at San Luis and at Albany for catalogue form, preparations for 

 the derivation of proper-motions and star places for the general cata- 

 logue, and a number of researches in various astronomical fields. 



The operations necessary to the completion of the observations 

 and of the general catalogue, while numerous and requiring long- 

 continued effort, are of little general interest in the main. Conse- 

 quently, only those steps which have more than a general interest 

 are reported, though they form but a small fraction of the total output 

 of effort. 



ABSOLUTE MAGNITUDE. 



In addition to the conclusions drawn in the last report of the De- 

 partment regarding absolute magnitudes, some other deductions of 

 interest have been made. For the material used there is a steady 

 progression in the size of the proper-motion with progression in the 

 size of the absolute magnitude, indicating increasing velocity of the 

 stars with decrease in absolute magnitude, though the effect is en- 

 hanced because the increase in the proper-motions is partly due to 

 decrease in distance. The same general effect of increase in velocity 

 with decrease in brightness is also shown through the treatment of the 

 radial velocities. There is a sharp increase in the velocity between 

 3.5 and 4.5 absolute magnitudes. The distribution of the absolute 

 magnitudes is fairly well represented by a probable-error curve, with 

 a maximum at +3.3 absolute magnitude and a probable error of ± 2.0. 

 Two velocity curves, one for giant stars and the other for dwarfs, 

 would probably fit the observed data more closely. There are some 

 marked deviations from the curve, especially that occurring between 

 +0.8 and +1.2 absolute magnitudes. A division of the absolute 

 magnitudes of the giant stars according to galactic latitude shovved no 

 appreciable change. 



SPACE MOTIONS. 



A further investigation of space motions has been undertaken, 

 employing the corrections for parallax which were previously deter- 

 mined. The radial velocities used were those determined at the Lick 

 and Mount Wilson Observatories, and the proper-motions were taken 

 from the Prehminary General Catalogue. Only those stars were used 

 where the material was sufficiently trustworthy, and even then com- 

 paratively small changes in the observed data would in many cases 



'Address: Dudley Observatory, Albany, N. Y. 



