Catalog-to-catalog reductions

Abstract

This paper completes a discussion of the retrieval of astrometric information from archival sources. The earlier work dealt with recording material such as astrographic plates and Schmidt plates. This work discusses star catalogs. In particular, the two principal systematic reduction problems associated with catalogs are treated anew: creating a uniform positional system and placing all catalogs of interest on it, and creating a standard proper motion system. The homogenization of the positional systems is performed via a variable size, infinitely overlapping generalization of the moving mean. Therefore, it has much wider applicability than the particular issue at hand and can be generalized, in several ways, to any dimensionality. The standardization of the proper motion systems relies on retrieving, as nearly possible, the older epoch positions implicit in a catalog and then bringing each epoch's positional system into agreement with an inertial reference frame in the manner just advocated. Proper motions are then recomputed from first principles. Moreover, when there are at least three positions available, large proper motions, an appreciable foreshortening term, or errors may be detected.