New reductions of the Astrographic Catalogue. Plate adjustments of the Algiers, Oxford I and II, and Vatican Zones

The U. S. Naval Observatory is in the process of making new reductions of the Astrographic Catalogue using a modern reference catalog, the ACRS, and new data analysis and reduction software. Currently ten AC zones have been reduced. This papers discusses the reduction models and results from the Algiers, Oxford I and II, and Vatican zones (those of the Cape zone are discussed elsewhere). The resulting star positions will be combined with those of the U.S. Naval Observatory's Twin Astrograph Catalog to produce a catalog of positions and proper motions in support of the Sloan Digital Sky Survey.