Back to Volume
Paper: Calibrating the USNO PMM
Volume: 61, Astronomical Data Analysis Software and Systems III
Page: 223
Authors: Henden, Arne A.; Pier, Jeffrey R.; Monet, David G.
Abstract: The USNO Precision Measuring Microdensitometer (PMM) uses a plateholder on an X-Y stage and a fixed CCD camera to digitize photographic materials accurately and efficiently. A number of projects will be undertaken eventually, but our first priority is the digitization and measurement of the both the initial (circa 1950s) and second (circa 1990s) epoch Palomar Observatory Sky Survey (POSS) plates. The end product of this effort will be a database of approximately 10**10 entries. Each entry will consist of the object's position (RA, DEC), proper motion, image shape parameters and photometry. Two test fields (in and out of the galactic plane) have been selected. Deep CCD photometry at the plate centers and edges has been performed to investigate the characteristic curve and astrometric color dependencies. CCD strip scans at constant declination have been taken to provide accurate relative astrometry and photometry across each plate. The accuracy of the PMM in matching the calibration data is discussed. The problems of removing the Schmidt plate geometrical distortions and vignetting are described.
Back to Volume