DETERMINATION OF ABSOLUTE PROPER MOTIONS OF STARS IN 21 OPEN CLUSTER

The mean absolute proper motions are computed for 21 open clusters by comparing the relative proper motions of their member stars with their absolute proper motions taken from the Four-Million Catalog of Positi ons and Proper Motions compiled in the Division of Astrometry at the S ternberg Astronomical Institute of the Moscow State University. From 7 0 to 302 stars in each cluster (a total of 2680 stars) are used for th e first time to determine the absolute proper motions of the open clus ters. The mean error in the proper-motion components of the Catalog is estimated to be 0.0041 arcsec yr(-1), and the maximum error to be sim ilar to 0.007 arcsec yr(-1). The parameters of the rotation curve comp uted even from such a small sample are in satisfactory agreement with the results obtained by Dambis et al. (1995) from the radial velocitie s and proper motions of classical Cepheids.