The AGK3U - An updated version of the AGK3

Details of construction of an updated version of the AGK3 are presented. Unlike the builders of the Positions and Proper Motions (PPM) catalog, we have gone forward in time to gain new positions to use to improve the AGK3 proper motions. The source of these new observations is the Palomar «Quick V» survey made for the construction of the Hubble Space Telescope Guide Star Catalog. We have been able to recover individual equatorial coordinates from a Schmidt plate with a typical standard deviation about the mean of 0.33″. Moreover, our means (i.e., the systematic errors) are at the 0.01″ level. These realistic, external errors compare favorably with the reduction of the AGK3 astrograph material (0.21″ per equatorial coordinate)