Available imaging data

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 reading both Understanding SDSS Imaging Data and the data model.

Methods for accessing these data are summarized on the data access pages.

SAS location	CAS table	Description
photoRunAll-dr9.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). JPG versions can be browsed (as in this example)
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)

The "datasweep" catalogs (calibObj-*.fits.gz) require each object to have a solid detection in at least one band and not all of the quantities are reported for each object. While they therefore form a subset of the full dataset in photoObj*.fits, for many purposes they are sufficient. For example, the BOSS galaxy and quasar target selection is performed on the basis of the sweeps.

For the images themselves, the 'corrected' frames have been flat-fielded and bias-subtracted; bad columns and cosmic rays have been interpolated over, sky has been subtracted, and they have been calibrated to nanomaggies per pixel.