Imaging data access tools

Access tools

See the description of DR8 data access for a full listing of the tools available. Users primarily interested in catalog parameters should usually use the CAS. Users who are interested in reanalyzing images themselves are encouraged to use the Science Archive Server.

In a nutshell, Catalog Archive Server (CAS) and CASJobs provide interfaces to a SQL database with all of the SDSS imaging results. The simplest place to start is the imaging query form.

The SAS has the same results available for browsing on the web and through wget and rsync access, as described on the Data Access page. The SAS provides access to the individual FITS images, directly through the directory structure, through its search interface and through its mosaicking tool. It also has a tool that allows one to check the imaging survey coverage.

In addition, as we explain below, there is a reduced form of the imaging catalogs in FITS format on the SAS called the "sweeps", which is about 326Gb of data and thus relatively portable.

Outline of tables

The major imaging results are contained in a few different file structures (on SAS) and database tables (in CAS), listed below. Of particular use in browsing and using these data is the full photoRunAll list of imaging runs, available either on CAS or in flat-file form as a FITS or Yanny file. Note that the links into SAS below bring you into the full directory tree; it is best not to wander there before first understanding the imaging basics and understanding how to use the data model.

SAS location	CAS table	Description
photoRunAll-dr8.fits (in BOSS_PHOTOOBJ; see datamodel)	Run	Metadata for each imaging run (one file, each around 2 Mb)
photoField-RUN-CAMCOL.fits (in BOSS_PHOTOOBJ; see datamodel)	Field	Metadata for each imaging field in a camcol (4,590 files total, each around 1.5Mb)
photoObj-RUN-CAMCOL-FIELD.fits (in BOSS_PHOTOOBJ; see datamodel)	photoPrimary (only primaries)	Photometric parameters for objects in each imaging field. (around 938,000 files total, each around 3.5Mb)
calibObj-RUN-CAMCOL-TYPE.fits.gz (in PHOTO_SWEEP; see datamodel)		"Sweep" data for each imaging camcol (4590 files total, one for each run, each around 70Mb)
photoEXT-RUN-CAMCOL.fits (in BOSS_PHOTOOBJ/external; see datamodels)	TWOMASS, TWOMASSXSC, USNO, First, RC3, ROSAT, properMotions	External catalog matches and ancillary information for each camcol. Only lists SDSS objects that match. Field-by-field version in subdirectories.
frame-BAND-RUN-CAMCOL-FIELD.fits.bz2 (in BOSS_PHOTOOBJ/frames; see datamodel)		Calibrated, sky-subtracted corrected frames (SDSS-III format)
Resolve information (in PHOTO_RESOLVE; see datamodel)		Information about the SDSS window function, including a list of all fields in window_flist.fits (336 Mb)