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---1.15, 1.0, 1.035 Integration time (s)---1800, 1800, 1200 Pixel scale (arcsec)---1.134, 1.134, 1.134 # Wed 09:35:54 05-Jun-2002 begin BFIT status 0 (Solution converged) variance 0.002002119 stdeviation 0.04474504 avsqerror 0.002000273 averror 0.04472441 avsqscatter 0.0011534 avscatter 0.03396175 chisqr 1.000923 msq 0.00193308 rms 0.04396681 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 3.668 0.2104808 -0.0274 0. errors 4 0. 0.00467914 0. 0. # Wed 09:36:55 05-Jun-2002 begin VFIT status 0 (Solution converged) variance 1.818566E-4 stdeviation 0.01348542 avsqerror 2.323986E-4 averror 0.01524463 avsqscatter 5.603344E-5 avscatter 0.007485548 chisqr 0.7825202 msq 1.766607E-4 rms 0.01329138 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 3.246 0.1009549 -0.0167 0. errors 4 0. 0.001344116 0. 0. # Wed 09:44:32 05-Jun-2002 begin UFIT status 0 (Solution converged) variance 0.001953959 stdeviation 0.04420361 avsqerror 0.00195244 averror 0.04418642 avsqscatter 0.001760506 avscatter 0.04195839 chisqr 1.000778 msq 0.001878807 rms 0.04334521 reference mU fitting (UB+BV+V)+u1+u2*XU+u3*UB+u4*UB*XU weights photometric parameters 4 u1 (constant) u2 (fit) u3 (constant) u4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 5.203 0.4756422 -0.0911 0. errors 4 0. 0.005368493 0. 0.