Data model: astromQAFields

General description: A summary file containing all information about the SDSS field astrometry QA, including offsets from each of the reference catalogs. For convenience, all of the information in the photoField files is copied over as well.

For the vectors in the data file that contain an element for each reference file, they are in the order: DR7, 2MASS, USNO-B, UCAC-2 plus r14, and UCAC-3.

Note that "UCAC-2 plus r14" is essentially the catalog that SDSS DR7 calibrated off of. The public version of UCAC-2 does not extend to declinations greater than about 40 deg; the USNO internal "r14" catalog supplements the data set in the North. If you are interested in flagging areas that have been miscalibrated relatived to this reference, the best way is to search for fields with DRA[3] or DDEC[3] greater than 0.1 arcsec.

An "ASTROMBAD" column is included that flags catastrophically bad offsets in fields relative to UCAC-2 plus r14. In particular, this means that the field is greater than 0.5 arcsec off; in most cases this indicates truly unusable astrometry.

Naming convention: astromQAFields.fits

Approximate size: 3 Gbytes.

File type: FITS

Read by products: photoop

Written by products: photoop

Required header keywords: (none)

Required column names:

• All fields in the photoField file.
• DRA[5] (float32): median RA offset within field relative to each reference (SDSS minus reference), in arcsec
• DDEC[5] (float32): median Dec offset within field relative to each reference (SDSS minus reference), in arcsec
• ASTROMBAD (int8): set to 1 if astrometry is catastrophically bad relative to UCAC-2 plus r14
• DPMRA (float32): median RA proper motion offset within field relative to SDSS DR7 (current minus DR7), in mas/yr
• DPMDEC (float32): median Dec proper motion offset within field relative to SDSS DR7 (current minus DR7), in mas/yr
• CHECKED[5] (int8): set if this field was able to be checked against each reference for position offsets
• PMCHECKED[5] (int8): set if this field was able to be checked against each reference for proper motion offsets
• BADFIELD[5] (int8): set if this field was flagged as bad individually relative to each reference (0.2 arcsec or more off)
• BADFIELDCAT[5] (int8): set if this field was flagged as catastrophically bad individually relative to each reference (0.5 arcsec or more off)
• BADFIELDGROUP[5] (int8): set if the median offset of the seven fields surrounding this field (that is from field-3 to field+3 on the camcol) is bad relative to each reference (0.1 arcsec or more off)
• BADPMFIELD[5] (int8): set if proper motions in this field were flagged as bad individually relative to each reference (5 mas/yr or more off)
• BADPMFIELDCAT[5] (int8): set if proper motions in this field were flagged as catastrophically bad individually relative to each reference (10 mas/yr or more off)
• BADPMFIELDGROUP[5] (int8): set if the median offset of proper motions in the seven fields surrounding this field (that is from field-3 to field+3 on the camcol) is bad relative to each reference (2.5 mas/yr or more off)