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The Yale/San Juan Southern Proper Motion program (SPM) is an extension of the Lick Observatory Northern Proper Motion program (NPM) to the southern hemisphere. Absolute proper motions with respect to faint galaxies and positions will be determined for approximately one million objects south of -17 degree declination. The purpose of the SPM has been broadened to also include the creation of a secondary reference system of stars within the range 15-18 visual magnitude.
We present here the first results for a pilot program area consisting of 40 SPM fields in a 1000 square-degree region around the South Galactic Pole. The magnitude distribution of the program stars has been specifically chosen so as to optimize their use in our galactic structure studies. Absolute proper motions and B,V photometry are determined for 50,000 stars in the SGP region. The internal error of the proper motions is 4-5 milliarcsec/year. A comparison of the proper motions derived from different diffraction grating images, different exposures, and different passband plates allows us to detect and correct systematic errors in the proper motions.
In addition to plate-to-plate and image-to-image analyses, we also expect to use the superb HIPPARCOS positions in order to improve our plate models and reduce both the random and systematic errors which remain in the derived positions and proper motions. Conversely, the absolute proper motions from the SPM and NPM programs will provide a needed link of the HIPPARCOS proper motion system to the extragalactic reference frame.
