DPOSS is a program to photograph and catalog the entire Northern Sky. Photographic plates, each covering 36 sq. deg., are taken at the Palomar 48" Oschin Telescope.
Three plates, in 3 different colors, are taken at each pointing. The plates
correspond to blue, red, and near-infrared colors. It takes 897 plates to
cover the sky in each color; therefore, a total of 2,691 plates will be taken, not counting those that need to be redone due to aircraft streaks, defects, etc. A detailed description of the photographic survey can be found here.
Once taken, the plates are sent to the Space Telescope Science Institute (STScI) to be scanned. The plates are converted to digital images by a machine which moves the plate over a collimated light source, recording the amount of light that passes through at each point.
These scans are then sent to Caltech, where catalogs of all the objects on each plate are generated. A specially developed software package, called SKICAT (Sky Image Cataloging and Analysis Tool) is used, which measures many characteristics of each object, and determines whether it is a star or galaxy.
Eventually, these catalogs will be released to the astronomical community as the Palomar-Norris Sky Catalog. This catalog will contain an estimated 50,000,000 (50 million) galaxies, and
2,000,000,000 (2 billion) stars.
Plates for the sky survey were donated by Eastman Kodak.
Partial funding for this project provided by the Norris Foundation.