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---1.2, 1.19, 1.19
Integration time (s)---600, 180, 60
Pixel scale (arcsec)---0.42, 0.42, 0.42

# Fri 14:06:08 10-May-2002
begin	UFIT
	status	0	(Solution converged)
	variance	0.001998436
	stdeviation	0.04470387
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.001998436
	msq		0.001870876
	rms		0.04325363
	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
		1.336326
		0.5622226
		-0.1036324
		0.
	errors	4
		0.06752726
		0.05396826
		0.01200154
		0.

# Fri 14:07:16 10-May-2002
begin	BFIT
	status	0	(Solution converged)
	variance	1.140663E-4
	stdeviation	0.01068018
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		1.140663E-4
	msq		9.695632E-5
	rms		0.00984664
	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
		-0.2246805
		0.2901735
		-0.03218131
		0.
	errors	4
		0.02321666
		0.01711643
		0.007003371
		0.

# Fri 14:08:16 10-May-2002
begin	VFIT
	status	0	(Solution converged)
	variance	1.785183E-4
	stdeviation	0.01336107
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		1.785183E-4
	msq		1.487653E-4
	rms		0.01219694
	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
		-0.3788421
		0.2121398
		0.001862769
		0.
	errors	4
		0.02861157
		0.02103328
		0.009731187
		0.