Go to sdss.org
DR7 Home
Where to Start
   Database (CAS)
   Files (DAS)
   Older Releases
About DR7
   Sky Coverage
   Data Processing
   Known Issues
   DR Papers


Up: Data Products Sections: Images - Object lists - Spectra - Tiling

Getting and using images

The Data Archive Server provides the survey images, called "corrected frames", as fpC*.fits files. See the fpC data model.

The Catalog Archive Server serves 3-color jpeg images generated from the g, r, i images as finding charts, cutouts for object lists and for point-and-click navigation of the sky.

The data access page contains various query forms to get images by coordinates, or to search for objects from the imaging and spectroscopic catalogs by redshift, object magnitude, color etc., and to retrieve the corresponding data from the archive.

There is a separate set of fpAtlas*.fits files, containing the "postage-stamp" images for individual objects from the photometric object lists. See how to read an atlas image.

New for DR7: Runs and Stripe 82 Databases

The DR7 Catalog Archive Server contains the imaging RUNS database, separate from the DR7 (Legacy + SEGUE) database. This database contains 530 imaging scans, some of which are not present in the main DR7 database, and thousands imaging fields from the beginnings and ends of DR7 strip scans which did not resolve into a complete rectangular stripe on the sky.

The DR7 Catalog Archive Server contains the Stripe82 database, distinct from the DR7 and RUNS databases, containing all imaging from SDSS stripe 82 along the Celestial Equator in the Southern Galactic Cap (Stripe 82). Subsets of the 303 individual stripe 82 scans were made public in previous data releases, but with DR7, we now make a coaddition (the Stripe 82 coadd) of about 47 South strip and 55 North strip scans into a scan in which objects are detected and cataloged about 2 magnitudes deeper than in any individual stripe82 scan. It includes a total of 303 runs (plus 2 coadd runs), covering any given piece of the approx. 270 deg2 area approximately 80 times.

All 303 runs covering Stripe 82 are part of the Stripe 82 database, which can be queried to search for variability (and propermotion, with a bit more effort). Only about one-quarter of the Stripe 82 scans were obtained in photometric conditions, the rest were taken under variable clouds and often poorer than normal seeing. For those runs which are non-photometric, an approximate calibration, using the photometric frames as reference, is derived and available in the CAS stripe82 database, for objects with RA > 310 or RA < 59 degrees.


  • Overestimation of sky levels near bright galaxies