col.   1    : ID, chip dependent (not relevant here)
cols.  2,  3: x, y position on the individual WFPC2 chips (pixels)
cols.  4,  5: RA, Dec (J2000)
cols.  6,  7: mag(F555W) and uncertainty
cols.  8,  9: mag(F814W) and uncertainty
cols. 10, 11: V and I magnitudes, using Holtzman's conversion equations
col.  12    : chip/flag (not relevant for the current purpose)