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1994DSS...1...0000: The Digitized Sky Survey: 102 CD-ROMs of images compressed by a factor of 10. The Space Telescope Science Institute (ST ScI) digitized Schmidt survey plates covering the entire sky to obtain the image data needed for construction of the Guide Star Catalog (GSC) and to pursue a number of research programs. The digitized version of the plates are of great utility in astronomical research but distribution of the scans has previously been impractical because of the massive volume of data involved (a total of about 600 Gbytes). However, the H-transform wavelet compression technique now makes such a distribution feasible. With funding from NASA Headquarters, compression of 1541 digitized images covering the entire sky began in June 1992. The 61 discs comprising Part I in this series of CD-ROM publications contain a complete imaging survey of the southern hemisphere (plate centers delta <= 0 degrees) constructed largely from the SERC J Southern Sky Survey and its Equatorial extension (see Table III of Lasker et al. 1990, hereafter Paper 1). These are deep (1800s-7200s) IIIa-J exposures obtained through a GG 395 filter, except for 94 short (240s) V-band exposures mostly at low Galactic latitudes (|b| <= 15 degrees) plus 2 plates covering the Large Magellanic Cloud and 2 short (300s) V-band exposures, each centered on one of the Magellanic Clouds (see Paper 1). The digitized images have been compressed by a factor of 10, on average, and are extremely faithful to the original data (cf. Section 8.3). The 61 discs contain a total of 896 compressed, digitized Schmidt images, an astrometric calibration database, and data access software. The 41 discs comprising Part II in this series contain a complete imaging survey of the northern hemisphere (plate centers delta >= 0 degrees) constructed from the 1950-55 epoch Palomar Observatory Sky Survey (POSS). These are deep (2400s-4200s) 103a-E exposures obtained through a red plexiglass filter and the original corrector. A digitized image of a single short (300s) IIIa-J exposure of M31, obtained through a GG 495 filter, is also included in this set. The POSS E survey data were not used in the construction of the GSC. We choose the POSS E data for northern hemisphere coverage because its limiting magnitude is comparable with that of the SERC Southern Sky Survey. The digitized images have been compressed by a factor of 10, on average, and are extremely faithful to the original data (cf. Section 8.3). The 41 discs contain a total of 645 compressed, digitized Schmidt images, an astrometric calibration database, and data access software. Questions, comments, and suggestions regarding this publication may be directed to: asp@bkyast.berkeley.edu (Internet), or (415) 337-5205 (FAX), or paper mail to Astronomical Society of the Pacific Dept. 10X 390 Ashton Avenue San Francisco, CA 94112-1787 USA A detailed presentation of the techinical and scientific aspects of these compressed data is being prepared (Postman et al. 1995); the information contained in this booklet provides a brief summary of the most important issues.
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