ACT Catalog

The ACT Catalog is an astronomical catalog, compiled by the US Naval Observatory (USNO), to provide accurate proper motions for the majority of stars in the Tycho Catalogue. Since the Tycho Catalogue is based on data collected by the Hipparcos satellite over a relatively short period, it gives only rough values of proper motions. The USNO solved this problem by combining Tycho positions with those of the Astrographic Catalogue that date from around 1900. The result of this long baseline for computations are proper motions for 988,758 stars, covering the entire sky, that are about an order of magnitude more accurate than those published in the Tycho Catalogue.