The following calibration format can be used directly in IRAF.digiphot.photcal.invertfit. The instrumental magnitudes mU, mB, and mV are -2.5*log(counts/s)+25. For the these images, the average parameters for UBV are the following: Airmass---1.32, 1.26, 1.25 Integration time (s)---1800, 480, 180 Pixel scale (arcsec)---0.42, 0.42, 0.42 # Mon 11:07:29 13-May-2002 begin UFIT status 0 (Solution converged) variance 3.194103E-4 stdeviation 0.01787205 avsqerror 1. averror 1. avsqscatter 0. avscatter 0. chisqr 3.194103E-4 msq 2.129402E-4 rms 0.01459247 reference mU fitting (UB+BV+V)+u1+u2*XU+u3*UB+u4*UB*XU weights uniform parameters 4 u1 (fit) u2 (fit) u3 (fit) u4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 1.679049 0.3572555 -0.0400845 0. errors 4 0.1001485 0.08258455 0.01287872 0. # Mon 11:08:08 13-May-2002 begin BFIT status 0 (Solution converged) variance 1.984439E-4 stdeviation 0.01408701 avsqerror 1. averror 1. avsqscatter 0. avscatter 0. chisqr 1.984439E-4 msq 9.922194E-5 rms 0.009961021 reference mB fitting (BV+V)+b1+b2*XB+b3*BV+b4*BV*XB weights uniform parameters 4 b1 (fit) b2 (fit) b3 (fit) b4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 -0.0829096 0.2040792 -0.005089185 0. errors 4 0.07697853 0.0647294 0.02438456 0. # Mon 11:08:45 13-May-2002 begin VFIT status 0 (Solution converged) variance 2.632159E-4 stdeviation 0.01622393 avsqerror 1. averror 1. avsqscatter 0. avscatter 0. chisqr 2.632159E-4 msq 1.754772E-4 rms 0.01324678 reference mV fitting V+v1+v2*XV+v3*BV+v4*BV*XV weights uniform parameters 4 v1 (fit) v2 (fit) v3 (fit) v4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 -0.3681273 0.2220466 0.0130948 0. errors 4 0.08020329 0.06855157 0.02642367 0.