The SPM4 Catalog contains absolute proper motions, celestial
coordinates, and B,V photometry for 103,319,647 stars and galaxies
between the south celestial pole and -20 degrees declination. The
catalog is roughly complete to V=17.5. It is based on photographic and
CCD observations taken with the Yale Southern Observatory's
double-astrograph at Cesco Observatory in El Leoncito, Argentina.