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---1.02, 1.07, 1.24 Integration time (s)---1800, 1800, 1200 Pixel scale (arcsec)---1.134, 1.134, 1.134 # Fri 16:21:54 31-May-2002 begin UFIT status 0 (Solution converged) variance 0.003266471 stdeviation 0.05715305 avsqerror 0.003265345 averror 0.0571432 avsqscatter 0.002231684 avscatter 0.0472407 chisqr 1.000345 msq 0.003107131 rms 0.05574164 reference mU fitting (UB+BV+V)+u1+u2*XU+u3*UB+u4*UB*XU weights photometric parameters 4 u1 (fit) u2 (fit) u3 (constant) u4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 4.97379 0.6303594 -0.0947 0. errors 4 0.07235418 0.0521051 0. 0. # Fri 16:33:27 31-May-2002 begin BFIT status 0 (Solution converged) variance 6.095189E-4 stdeviation 0.02468844 avsqerror 6.072376E-4 averror 0.02464219 avsqscatter 3.198662E-4 avscatter 0.0178848 chisqr 1.003757 msq 5.959740E-4 rms 0.02441258 reference mB fitting (BV+V)+b1+b2*XB+b3*BV+b4*BV*XB weights photometric parameters 4 b1 (constant) b2 (fit) b3 (constant) b4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 3.652 0.2300204 -0.0153 0. errors 4 0. 0.002494009 0. 0. # Fri 16:33:58 31-May-2002 begin VFIT status 0 (Solution converged) variance 9.247058E-4 stdeviation 0.03040897 avsqerror 9.236346E-4 averror 0.03039136 avsqscatter 5.107867E-4 avscatter 0.02260059 chisqr 1.00116 msq 9.062117E-4 rms 0.03010335 reference mV fitting V+v1+v2*XV+v3*BV+v4*BV*XV weights photometric parameters 4 v1 (constant) v2 (fit) v3 (constant) v4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 3.22 0.1205604 -0.0141 0. errors 4 0. 0.00257552 0. 0.