In January, the SDSS collaboration released Data Release 8, including a much larger area of sky, with photometric data for nearly 500 million sky objects, and spectra for more than 1.5 million.
A small part of the sky as seen by Data Release 8
As always, data from all previous releases is still available also. New this week is the ability to cross-match sky objects between Data Release 7 and Data Release 8. If you have object IDs and parameters for a specific object from DR7, you can query for the same object in DR8.
The cross-matching is available three different ways:
SpecDR7: This is a unique match between a DR8 SpecObjAll and a DR7 photoprimary within 1 arcsec. DR7 PhotoTag columns and relevant DR7 ProperMotions are also included for convenience.
PhotoPrimaryDR7: This is a unique match between a DR8 photoprimary and a DR7 photoprimary, and matches between different run/camcol/field are allowed. The match radius is 1 arcsec. The table contains the DR8 and DR7 objids, the distance between them and the DR7 PhotoTag quantities.
PhotoObjDR7: This is a unique match between a DR8 photoobj and a DR7 photoobj, and matches are restricted to the same run/camcol/field are allowed. The ...