Sloan Digital Sky Survey Photometric Catalog (DR4) (SDSS DR4)

WCSTools Catalogs

The Sloan Digital Sky Survey will map one-quarter of the entire sky and perform a redshift survey of galaxies, quasars and stars. Data Release 4 (DR4) covers 6670 square degrees and catalogs 180 million unique objects from CCD images taken through five filters (u-3655A, g-5155A, r-6480A, i-7105A, z-8630A) Photometry is better than 3%, and positions are accurate to about 0.1 arcsecond in each coordinate.

Software for searching the SDSS Photometric Catalog over the web has been inWCSTools since release 3.5.2.
scat (ssdss) searches the catalog by sky location or number.
imcat (imsdss) lists the objects in the region covered by a FITS or IRAF image with world coordinate system (WCS) information in its header.
imwcs (imwsdss) fits a WCS to a FITS or IRAF image using the SDSS Photometric Catalog as a reference.

DSS DR4 Imaging Sky Coverage
(Aitoff projection of Equatorial coordinates)

(Click on map for galactic coordinates)

SDSS DR4 Imaging coverage

The official SDSS designation for an object is
where the coordinates are truncated, not rounded. This format must be used at least once for every object listed in a paper using SDSS data. ssdss returns an 18-digit identifier which comes from the SDSS catalog server.

When abbreviating the object name in the text please use the "J" to indicate the equinox of the coordinates. For example SDSS J123456.89-012345.6 could be abbreviated as SDSSJ1234 or SDSSJ1234-0123. Please refer to the CDS dictionary on SDSS for further information.

type is the morphological classification of the object
UNKNOWN0Unknown: Object type is not known.
COSMIC_RAY1Cosmic-ray track (not used).
DEFECT2Defect: Object is caused by a defect in the telescope or processing pipeline. (not used)
GALAXY3Galaxy: An extended object composed of many stars and other matter.
GHOST4Ghost: Object created by reflected or refracted light. (not used)
KNOWNOBJ5KnownObject: Object came from some other catalog (not the SDSS catalog). (not yet used)
STAR6Star: A a self-luminous gaseous celestial body.
TRAIL7Trail: A satellite or asteriod or meteor trail. (not yet used)
SKY8Sky: Blank sky spectogram (no objects in this arcsecond area).