The Solar Photograph Archive of the Mount Wilson Observatory - A Resource for a Century of Digital Data

The solar telescopes and spectroheliographs of the Mount Wilson Observatory were among the earliest modern facilities for the study of the solar surface. The photographic collection of the solar program at Mt. Wilson begins in 1894 and continues to the present day. A program to digitize and distribute some of the images in this collection was begun at UCLA in 2003 and is now making available the first of the catalogued and catagorized images from the Ca K sequence. Most of the instrumentation with which the images were obtained is still available although in a disassembled form. Original logbooks have been digitized and associated with the images so that a maximum of scientific return can be obtained from the data base. The present range of images available from: http://www.astro.ucla.edu/&~slash;ulrich/MW&_slash;SPADP/CaK&_slash;fits/ extends from late 1915 to mid-1925. Each image has been digitized with 12-bit precision and represented in a 16-bit format. These images are each 13 Mbytes in size and larger than will be the final product images since not all image defects have been mitigated at this time. The radii and centers of the solar images have been determined and are included in the available data files. Optical vignetting by the system introduces an intensity gradient of known magnitude that can be used to help characterize the photograph plates. The roll angle of the images has yet to be determined.