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---1.17, 1.26, 1.38 Integration time (s)---1800, 1800, 1800 Pixel scale (arcsec)---1.134, 1.134, 1.134 # Thu 13:55:49 06-Jun-2002 begin UFIT status 0 (Solution converged) variance 0.005402638 stdeviation 0.07350264 avsqerror 0.005401331 averror 0.07349374 avsqscatter 0.004012552 avscatter 0.06334471 chisqr 1.000242 msq 0.004754321 rms 0.06895158 reference mU fitting (UB+BV+V)+u1+u2*XU+u3*UB+u4*UB*XU weights photometric parameters 4 u1 (fit) u2 (fit) u3 (fit) u4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 5.172179 0.5305759 -0.1119325 0. errors 4 0.08649484 0.05988634 0.02177441 0. # Thu 13:57:11 06-Jun-2002 begin BFIT status 0 (Solution converged) variance 0.001453105 stdeviation 0.03811961 avsqerror 0.001451622 averror 0.03810015 avsqscatter 6.935023E-4 avscatter 0.02633443 chisqr 1.001022 msq 0.00132489 rms 0.03639903 reference mB fitting (BV+V)+b1+b2*XB+b3*BV+b4*BV*XB weights photometric parameters 4 b1 (fit) b2 (fit) b3 (fit) b4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 3.661739 0.2671157 -0.01449246 0. errors 4 0.03553796 0.02340672 0.01132262 0. # Thu 13:58:28 06-Jun-2002 begin VFIT status 0 (Solution converged) variance 5.154423E-4 stdeviation 0.02270336 avsqerror 5.132827E-4 averror 0.02265574 avsqscatter 2.550269E-4 avscatter 0.01596956 chisqr 1.004208 msq 4.638981E-4 rms 0.02153829 reference mV fitting V+v1+v2*XV+v3*BV+v4*BV*XV weights photometric parameters 4 v1 (fit) v2 (fit) v3 (fit) v4 (constant) derivatives 4 0.1 0.1 0.1 0.1 values 4 3.206747 0.1810213 -0.01222482 0. errors 4 0.0240465 0.01481911 0.007297779 0.