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Digitised Sky Survey

The Digitised Sky Survey comprises a set of all-sky photographic surveys in E, V, J, R and N bands conducted with the Palomar and UK Schmidt telescopes. These images have been digitised by the Catalogs and Surveys Branch (CASB) of the Space Telescope Science Institute. The 6.5-degree x 6.5-degree plates are scanned using a modified PDS microdensitometer to a pixel scale of about 1.7 arcseconds per pixel for the POSS, SERC, and Palomar Quick-V surveys, and to about 1.0 arcseconds per pixel for the POSS-II surveys. These scanned images are typically large (0.4GB @ 14000x14000 pixels, or 1.1GB @ 23040x23040 pixels) and are difficult to access quickly. To provide convenient access to the data, the images have been compressed using a technique based on the H-transform to reduce the data volume by a factor of 7 whilst preserving the signal. These H-compressed images are available for download from LEDAS.

DSS-I Southern data

Data from the SERC Southern Sky Survey and the SERC J Equatorial extension. These are typically deep, 3600s exposures on IIIa-J plates with a Schott GG395 filter (a combination roughly similar to B-band). Also included are 94 short (1200s) V exposures typically at Galactic latitudes below 15 degrees. Special exposures are included in the regions of the Magellanic clouds.

DSS-I Northern data
The northern hemisphere is covered by 644 plates from the Palomar Observatory Sky Survey red (E-band) plates taken in 1950-55 epoch.

Photometric analysis
Note that there are considerable caveats attached to direct photometric analysis of the H-compressed DSS images provided by this service. See the STSci DSS pages for more information. An approximate photometric calibration of the DSS images has been calculated.

Please see the copyright restrictions on use of these data.

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