Astrographic Catalog

The Astrographic Catalog was to be the product of an effort begun in 1887 to photograph the entire sky down to magnitude 11.5. As conceived, it would be a reference for a simultaneous analogous project, the Cart du Ciel covering the sky to magnitude 14. The effort was carried on for decades, with more than twenty observatories splitting the work. Eventually, the USNO took up the effort, evolving into more modern efforts. The plates produced have been of use for comparison with recent efforts such as Hipparcos, for the study of proper motion