General description: Summary image of offsets in astrometry relative to a reference catalog. The image is a grid in RA and Dec, and the values are the mean over all primary stars used in the astrometry QA software. There are several versions of this image as defined below.
CAT: Reference catalogs that we compare to include: SDSS DR7 ("DR7"), 2MASS ("2mass"), USNO-B ("usnob"), UCAC-2 plus r14 ("ucac"), and UCAC-3 ("ucac3"). UCAC-2 only covers up to around declination of 40 deg; "r14" is an internal USNO product that was used to calibrated SDSS DR7. Finally, we compare to a version of the DR8 catalog that includes color corrections omitted in the official catalog ("sdssColor"). Note that the actual DR8 results to which we compare the references are in the "sdss" subdirectory.
TYPE: We store the right ascension ("dra") and declination ("ddec") offsets for all catalogs. For "DR7" we also store the proper motion offsets ("dpmra" and "dpmdec"); we only compare proper motions for stars in the same run. For "sdssColor" we store an image of the DR8 proper motion field itself, for reference.
NRA, NDEC: Versions are stored at several resolutions, as indicated in the file names. These give the size of thee image in the FITS file
Units of position are in arcsec; units of proper motion are in mas/yr.
Naming convention: astromQAImage-CAT-TYPE-NRA-NDEC.fits
Approximate size: 100 Mbytes.
File type: FITS
Read by products: photoop
Written by products: photoop