Format for the Table of FIRST-APM Optical Counterparts

From McMahon, White, Helfand & Becker, 2001, "Optical Counterparts for
70,000 Radio Sources: APM Identifications for the FIRST Radio Survey",
ApJSupp, in press

Column  Name        Description
------  ----        -----------
1-2     RA, Dec     radio source coordinates (epoch J2000.0)
3-5     dRA, dDec   offsets (arcsec) to the optical object in RA and Dec
5       Sep         radius (arcsec) to the optical object
6       Ecl         APM classification on E plate
7       Epsf        APM psf parameter on E plate
8       Emag        E (red) magnitude
9       Ocl         APM classification on O plate
10      Opsf        APM psf parameter on O plate
11      Omag        O (blue) magnitude 
12      O-E         Color
13      Plate       Number of POSS-I plate
14      Fpeak       FIRST peak radio flux density (mJy)
15      Fint        FIRST integrated radio flux density (mJy)
16      Maj         FIRST source deconvolved major axis (FWHM, arcsec)
17      Min         FIRST source deconvolved minor axis (FWHM, arcsec)
18      PA          FIRST position angle for major axis (degrees)

Notes on parameters:

- APM positions and magnitudes have been calibrated as described in the
  paper.
- The classification codes (Ecl, Ocl) are -1=stellar, 1=non-stellar,
  2=blended, 0=noise.
- The Epsf and Opsf parameters measure by how many sigma the object
  deviates from being a point-source.
- Negative magnitudes indicate that source is undetected on the plate.
  In that case, the absolute value of the magnitude is an upper limit.
- The O-E color is -9.99 if the object is detected on only one plate.
- The radio parameters are described in more detail in White, Becker,
  Helfand, & Gregg (1997, ApJ, 475, 479) and on the FIRST web pages
  (http://sundog.stsci.edu).
- Negative values for the FIRST major and minor axes indicate that the
  source size before deconvolution was smaller than the beam, so the
  source is unresolved along that axis.