INTRODUCTION

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 related research programs. Copies of the GSC are made available to the scientific community and general public through the ST ScI and the Astronomical Society of the Pacific(ASP), respectively. The digitized versions of the plates are of great utility in astronomical research as well, 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 nowmakes such a distribution feasible. With funding from NASA Headquarters,compression of 1479 digitized images covering the entire sky began in June 1992.

Part I of the CD-ROM publications comprises 61 discs, and contains a complete imaging survey of the southern hemisphere (plate centers declination <=0 degrees) constructed largely from the SERC Southern Sky Survey and the SERC J Equatorial extension (see Table III of Lasker et al. 1990).These are deep (3600 s) IIIa-J exposures obtained through a GG 395 filter,except for 94 short (1200 s) V-band exposures mostly at low galactic latitudes(|b| <= 15 degrees) plus 2 plates covering the Large Magellanic Cloud and 2 veryshort (300 s) V-band exposures, each centered on one of the Magellanic Clouds. The digitized images have been compressed by a factor of 10, onaverage, and are extremely faithful to the original data (cf. section 7.3).These 61 discs contain a total of 896 compressed, digitized Schmidt images.

Part II of this publications is the 583 E (red) plates with centers declination>= +6 degrees from the 1950-55 epoch Palomar sky survey.


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