
for choosing the bright (tied-down) stars, these are used:

MAG_LIM                 &MAG_LIM        -- faintest stars used
SIGMA_LIM               &SIGMA_LIM      -- lowest S/N used (sigma = 1/(S/N))
STAR_SCATTER            &STAR_SCATTER   -- max scatter for a star to be include in the fits 
IMAGE_SCATTER           &IMAGE_SCATTER  -- max scatter for an image to be kept in the fit
IMAGE_OFFSET            &IMAGE_OFFSET   -- max zero point offset of an image to be kept in the fit
STAR_CHISQ              &STAR_CHISQ   -- max chisq for a star  to be include in the fits 
STAR_TOOFEW             &STAR_TOOFEW   -- star must have more than this good measurements to be used
IMAGE_TOOFEW            &IMAGE_TOOFEW   -- image must have more than this good measurements to be used
IMAGE_GOOD_FRACTION     &IMAGE_GOOD_FRACTION   -- image must have more than this (good measurements/all meas) to be used


GSCFILE                 GSCFILE   -- source for database sky table if missing
CATDIR                  CATDIR   -- catdir
CATMODE                CATMODE   -- output format for DVO tables (should not be used by relphot?)
CATFORMAT              CATFORMAT   -- output format for DVO tables (should not be used by relphot?)
PHOTCODE_FILE          MasterPhotcodeFile   -- source for photcode table if missing
SKY_DEPTH              SKY_DEPTH)) { SKY_DEPTH = 2; } -- output sky partition depth (default is 2, should not be used by relphot)
ZERO_PT                &ZERO_POINT   -- reference internal zero point, should not be needed (defined by DB)

CAMERA_CONFIG          CameraConfig   -- source of camera description, used for generating correction grid
MOSAICNAME             MOSAICNAME   -- name to define relationship between chip and camera 
GRID_TOOFEW            &GRID_TOOFEW   -- correction grid cell must have more than this stars (or is nan)
RELPHOT_GRID_X         &RELPHOT_GRID_X  -- number of grid cells per chip (x)
RELPHOT_GRID_Y         &RELPHOT_GRID_Y  -- number of grid cells per chip (y)
RELPHOT_GRID_BINNING   &RELPHOT_GRID_BINNING  -- ???
