Select which parameters you want to examine:
'astrom' Table Parameters
The 'astrom' database table stores information describing the astrometric fit to each POSS I field in
the MAPS Catalog. The following astrometric fit parameters are stored for each field in the MAPS Catalog:
||MAPS POSS I Field Name
||MAPS POSS I Field Number
||Astrometric catalog used for the data reduction. Either 'lick' for the Lick Northern Proper Motion Catalog or 'acrs' for the Astrographic Catalog of Reference Stars (ACRS).
||Epoch used for astrometric fit. Always '1950'.
||The horizontal and vertical zero point corrections applied to data before astrometric reduction (in microns).
||Initial rotation of astrometric fit (in degrees).
||The number of calibration stars used in astrometric calibration.
||The center of the plate (in ERE).
||The center of the plate in equatorial B1950.0 coordinates on the FK4 system used for the astrometric fit.
||The center of the plate in ecliptic J2000.0 coordinates on the FK5 system (precessed from ra_ctr, decl_ctr).
||The center of the plate in Galactic coordinates on the lII system (precessed from ra_ctr, decl_ctr).
||The RMS of the Right Ascension and Declination fit (in arcseconds).
|dx, x_x, x_y, x_xr2, dy, y_x, y_y, y_yr2
||These are the coefficients of the plate solution used (corresponding to
dX, X|x, X|y, X|xr, dY, Y|x, Y|y, Y|yr2 in the equations below).
The plate model that maps these modified coordinates, (x,y) to standard
coordinates on the celestial sphere (i.e. the focal-length-normalized
gnomic projection, (X,Y), of RA and Dec) is given by:
X = dX + (X|x)*x + (X|y)*y + (X|xr2)*(r^2) where r^2 = x^2 + y^2
Y = dY + (Y|x)*x + (Y|y)*y + (Y|yr2)*(r^2)
dX and dY are given in microns, and represent the difference between the
true and nominal plate centers. The remaining terms are dimensionless
derivatives. Note that one cannot apply the plate solution coefficients
directly to the plate positions in the MAPS catalog because the steps of
correcting for distortion, recentering, rotating, flipping, and
normalization by focal length are all performed internally in the data reduction before this
astrometric fit is applied.