The present catalog is a subset of the third data release of the Sloan Digital Sky Survey (SDSS), restricted to primary and secondary photo objects (i.e. objects from PhotoPrimary of PhotoSecondary tables) and restricted to the columns described in the "Byte-by-Byte" description below. The complete SDSS data release 3 catalog is available from http://www.sdss.org/dr3/ The Sloan Digital Sky Survey (SDSS) will map in detail one-quarter of the entire sky, determining the positions and absolute brightnesses of more than 100 million celestial objects. It will also measure the distances to more than a million galaxies and quasars. Apache Point Observatory, site of the SDSS telescopes, is operated by the Astrophysical Research Consortium (ARC). Funding for the SDSS has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS is a joint project of The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Korean Scientist Group, Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. All details about ADSS at http://www.sdss.org/dr3/