Where to Start
About DR6
News and Updates
Data Products
Data Access
Sky Coverage
Data Flow
Known Problems
Help and Feedback

The Sloan Digital Sky Survey (see www.sdss.org for general information) will map one-quarter of the entire sky and perform a redshift survey of galaxies, quasars and stars. The DR6 is the sixth major data release and provides images, imaging catalogs, spectra, and redshifts for download. It is the first data release of SDSS-II, an extension of the original SDSS consisting of three subprojects: Legacy, SEGUE and a Supernova survey. The first public data release from the Supernova Survey is available at www.sdss.org/drsn1/DRSN1_data_release.html

About DR6 explains what is new in DR6, and lists remaining or new caveats and subtleties in the data.

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.


Footprint area
Total cataloged in CAS9583 sq. deg.
Legacy8417 sq. deg.
SEGUE1592 sq. deg. of images in DAS
1166 sq. deg. of catalogs in CAS
Supernova Survey~300 sq. deg., repeated >40 times
M31 / Perseus scan26 sq. deg.
Low galactic latitude fields ("Orion" runs) 832 sq. deg.
Imaging catalog 287 million unique objects (SEGUE: 57 million, Legacy: 230 million)
Data volume
images10.0 TB
catalogs (DAS, fits format)2 TB
catalogs (CAS, SQL database)4 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
Regular CAS and DAS
r u-g g-r r-i i-z
2% 3% 2% 2% 3%
Only Ubercal table in CAS
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 7425 sq. deg.
Legacy 6860 sq. deg.
SEGUE 565 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)
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 1,271,680 1,163,520 108,160
Galaxies 790,860 790,220 640
Quasars (z <2.3) 90,108 89,458 650
Quasars (z ≥2.3) 13,539 12,892 647
M stars and later 69,052 64,895 4,157
Other stars 218,019 126,351 91,668
Sky spectra 68,770 59,843 8,927
Unknown 21,332 19,861 1,471
640 spectra are observed simultaneously on one plate. There are:
Data volume
calibrated spectra ("2d")80 GB
spectra, redshifts, line measurements ("1d")230 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.

This is version v6_20081024_0621 . This page was last modified on $Date: 2008/06/11 19:48:56 $ (UT).

If you are using Netscape 4.x and see oversized fonts, please look at the workaround on the Credits page.


BUG in spectroscopic synthetic magnitudes: mag_0,mag_1, mag_2 (they are u,g,r not g,r,i) in DR6 CAS and in spSpec DAS headers

The DR6 paper (Adelman-McCarthy, J.K. et al. 2008, ApJS, 175, 297-313) has appeared in print.

Imaging Sky Image
SDSS DR6 Imaging Sky Coverage (Aitoff projection of Equatorial coordinates)

Spectral Sky Image
SDSS DR6 Spectral Sky Coverage (Aitoff projection of Equatorial coordinates)

Imaging Sky Image
SEGUE DR6 Imaging Sky Coverage (Aitoff projection of Equatorial coordinates)

Spectral Sky Image
SEGUE DR6 Spectral Sky Coverage (Aitoff projection of Equatorial coordinates)