In order to support HST operations
and provide a service to the astronomical community,
has digitized the photographic Sky
Survey plates from the Palomar and UK Schmidt telescopes.
Each plate covers 6.5 x 6.5 degrees of the sky and have
digitized using a modified PDS microdensitometer with a pixel
size of either 25 or 15 microns (1.7 or 1.0 arcsec respectively).
These images are 14000x14000 (0.4GB) or 23040x23040 pixels
(1.1GB) in size and are difficult to access quickly. To
convenient access to these data, the images have been compressed
using a technique based on the
H-transform to reduce the data volume. Although the technique
is lossy, it is adaptive so that it preserves the signal
well. We typically compress the data by a factor of 7, but
much higher compression ratios are possible. These compressed
data are then placed on CDROM for distribution and archived
locally on a 1 terabyte RAID array for rapid access. Users
can then easily retrieve
image data for any part of the sky. The first epoch
images have already been published on CDROM, and the second
POSS-II and SES surveys have been
distributed on CDROM to a small number of institutions
who are supporting the CASB effort
to digitize and compress these survey plates. All of the
data is available to the community through web sites at
most of these centers.
read the fine print:
data use policy
We wish to
thank the following institutions for supporting
STScI with the publication of the DSS.
Without their involvement, this project may not have been completed!
Beijing Astronomical Observatory
Canadian Astronomical Data Center
Centre de Donnee Stellaire
European Southern Observatory
International GEMINI project
National Astronomical Observatory Japan
Royal Observatory Edinburgh