The Southern Proper Motion Program: A Status Report

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Session 42 -- Astrometry
Display presentation, Wednesday, 1, 1994, 9:20-6:30

[42.03] The Southern Proper Motion Program: A Status Report

Vera Kozhurina-Platais, Imants Platais, Terrence M. Girard, William F. van Altena, (Yale Univ.), Carlos E. L\'{o}pez (Felix Aguilar Obs.), Wen Zhang Ma (Beijing Normal Univ.), Lennart Lindegren (Lund Obs.)

We present the status of the Yale/San Juan Southern Proper Motion program (SPM) which is the southern hemisphere extension of the Lick Observatory Northern Proper Motion Program (NPM) with respect to faint galaxies. In addition to providing absolute proper motions for approximately one million stars, the scope of the SPM has been broadened to include the creation of a secondary positional reference system of faint stars at a density of 10 per square degree, within the range 15-18 visual magnitude. Presently, we are analyzing the PDS microdensitometer measures of 40 fields, comprising 1000 square degrees, in a pilot region around the South Galactic Pole (SGP). This SGP pilot study will yield absolute proper motions, positions and B,V magnitudes for 40,000 stars.

Possible sources of systematic errors in the final proper motions and positions have been investigated thoroughly. Of primary concern, is the presence of a magnitude equation in the plate material, believed to be due to decentered optical elements in the double astrograph at El Leoncito, Argentina. The telescope model has benefited from a direct comparison to the highly accurate HIPPARCOS positions, a preliminary subset of which were made available specifically for this purpose (Lindegren et al. 1994, A \& A in press). The multiple images per star on each plate, due to two exposures and an objective diffraction grating, help us to predict and correct for systematic effects within each image system. Parallel reductions using blue and visual passband plates in each field, in addition to the overlap regions of adjacent fields, provide a means of estimating the final absolute proper motion accuracy.

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