Space velocities of southern globular clusters .1. Astrometric techniques and first results

We present the first results of a program involving the determination of absolute proper-motions with respect to galaxies for a sample of southern globular clusters. Special attention has been given to understanding the systematics related to the plate material, the behavior of different reduction procedures, and the contribution of the reference-system proper-motion distribution and mean motion to the final solution. We have developed a local-type astrometric solution which overcomes most of the systematics, such that our limit in the absolute proper-motion precision is set by the centering accuracy and numbers of images of galaxies and cluster stars. Space velocities are derived for NGC 288, NGC 1851, NGC 6362, NGC 6584, and NGC 6752 and their kinematics are discussed in the view of halo subdivisions and Galaxy formation scenarios. (C) 1997 American Astronomical Society.