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The Sloan Digital Sky Survey (see www.sdss.org for general information) mapped one quarter of the entire sky and performed a redshift survey of galaxies, quasars and stars. Data Release 7 (DR7) is the seventh major data release and provides images, imaging catalogs, spectra, and redshifts for download. It is the final data release of SDSS-II, an extension of the original SDSS consisting of three subprojects: The Legacy Survey, SEGUE and a Supernova survey.

About DR7 explains what is new in DR7, and lists remaining or new caveats and subtleties in the data.

This site is designed primarily to provide access to Data Release 7 for professional astronomers. Members of the public, including educators, can explore DR7 by starting at the SkyServer website.

Please refer to the credits page for our sources of funding, participating institutions, and how to acknowledge the use of SDSS data in your publications. Please also note how to refer to SDSS sources in your publications using the proper IAU nomenclature for SDSS sources.

The Sloan Digital Sky Survey is continuing through the Third Sloan Digital Sky Survey (SDSS-III). More information on that survey is available at www.sdss3.org. SDSS-III has completed its two subsequent data releases, Data Release 9, and Data Release 8 (DR8).

Data access

The data products page describes which data SDSS produces. Fits images, spectra and catalog tables are served by the Data Archive Server (DAS). You can also search and browse all catalogs and jpeg images through the Catalog Archive Server (CAS) database. For an overview of the various search forms, see the data access page.


Footprint area
Total cataloged in CAS11663 sq. deg.
Legacy unique8423 sq. deg.
Legacy NGC ellipse7646 sq. deg.
SEGUE3240 sq. deg.
Supernova Survey~300 sq. deg., repeated ~80 times
M31 / Perseus / Sgr / SGP scans46 sq. deg.
Low galactic latitude fields ("Orion" runs) 832 sq. deg.
Imaging total area in DAS (multiple scans counted multiple times) 45,000 sq. deg. (1.3 million frames/filter)
Imaging catalog 357 million unique objects (SEGUE: 127 million, Legacy: 230 million)
Data volume
images (fits)15.7 TB
other data products (catalogs, masks, jpeg images, etc.) (DAS, fits format)26.8 TB
catalogs (CAS, SQL database)18 TB
Average wavelengths and magnitude limits
(95% detection repeatability for point sources)
u g r i z
3551Å 4686Å 6165Å 7481Å 8931Å
22.0 22.2 22.2 21.3 20.5
PSF width 1.4" median in r
Pixel size 0.396"
Exposure time for each pixel 53.9 s
Photometric calibration
r u-g g-r r-i i-z
2% 3% 2% 2% 3%
r u-g g-r r-i i-z
1% 2.2% 1.5% 1.5% 1.5%
Astrometry < 0.1" rms absolute per coordinate


Spectroscopic area
Total 9380 sq. deg.
Legacy 8032 sq. deg.
SEGUE 1348 sq. deg.
Wavelength coverage 3800-9200Å
Resolution 1800-2200
Signal-to-noise >4 per pixel at g=20.2
Redshift accuracy 30 km/sec rms for main galaxy sample (from repeat observations)
RV accuracy (systematics, for stars) 1.8 km/s systematics (SEGUE plate-to-plate wavelength solutions)
RV accuracy (total errors, for stars S/N per pixel = 27) 5.5 km/s rms (SEGUE matched plate comparisons, near g=18th mag)
Target magnitude limits for main samples Galaxies: Petrosian r <17.77
Quasars: PSF i <19.1 (20.2 for objects likely at z>2.3)
Spectroscopic catalog
Class N(total) N(main) N(SEGUE)
All 1,640,960 1,374,080 266,880
Galaxies 929,555 928,567 988
Quasars (z <2.3) 104,740 103,121 1,619
Quasars (z ≥2.3) 16,633 15,411 1,222
M stars and later 84,047 76,125 7,922
Other stars 380,214 150,748 229,466
Sky spectra 97,398 75,209 22,189
Unknown 28,383 24,767 3,616
640 spectra are observed simultaneously on one plate. There are:
  • 1802 Legacy ("main-survey") plates,
  • 86 repeat observations ("extra plates") of 77 distinct Legacy plates,
  • 676 observations of 660 distinct special plates, including
  • 410 observations of 212 distinct special plates taken under SEGUE.
Data volume
exposures and calibrated spectra ("2d")3.3 TB
spectra, redshifts, line measurements ("1d")450 GB

Previous data releases

For reference, we provide links to earlier data releases. The current data release always provides both the largest sky coverage and the highest-quality data and reductions.

Funding for the SDSS and SDSS-II was provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS was managed by the Astrophysical Research Consortium for the Participating Institutions.

This is version $Name: $. This page was last modified on $Date: 2013/08/01 16:55:35 $ (UT).

DR10, the current data release from SDSS-III, is released July 30, 2013!

DR9, from SDSS-III, is released Aug 1, 2012!

DR8, the first data release from SDSS-III, is available.

A new release of the Quasar Catalog complete through DR7 is now available

SDSS Mirror sites to bookmark are listed here

A paper describing the SEGUE survey is available.

A paper describing DR7 is available.

More details...

Imaging Sky Image
Legacy DR7 Imaging Sky Coverage (Aitoff projection of Equatorial coordinates)

Spectral Sky Image
Legacy DR7 Spectral Sky Coverage (Aitoff projection of Equatorial coordinates)

Imaging Sky Image
SEGUE DR7 Imaging Sky Coverage (Aitoff projection of Equatorial coordinates)

Spectral Sky Image
SEGUE DR7 Spectral Sky Coverage (Aitoff projection of Equatorial coordinates)