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, 1.04, 1.05
Integration time (s)---900, 900, 900
Pixel scale (arcsec)---0.61, 0.61, 0.61

# Wed 16:31:30 15-May-2002
begin	BFIT
	status	0	(Solution converged)
	variance	0.00552923
	stdeviation	0.07435879
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.00552923
	msq		0.005390999
	rms		0.07342342
	reference	mB
	fitting		(BV+V)+b1+b2*XB+b3*BV+b4*BV*XB
	weights		uniform
	parameters	4
		b1	(constant)
		b2	(fit)
		b3	(constant)
		b4	(constant)
	derivatives	4
		0.1
		0.1
		0.1
		0.1
	values	4
		1.74
		0.4519812
		0.061
		0.
	errors	4
		0.
		0.008966669
		0.
		0.

# Wed 16:32:03 15-May-2002
begin	VFIT
	status	0	(Solution converged)
	variance	0.001663874
	stdeviation	0.04079061
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.001663874
	msq		0.001622277
	rms		0.0402775
	reference	mV
	fitting		V+v1+v2*XV+v3*BV+v4*BV*XV
	weights		uniform
	parameters	4
		v1	(constant)
		v2	(fit)
		v3	(constant)
		v4	(constant)
	derivatives	4
		0.1
		0.1
		0.1
		0.1
	values	4
		1.532
		0.3446285
		0.0075
		0.
	errors	4
		0.
		0.004954617
		0.
		0.

# Thu 15:49:25 11-Jul-2002
begin	UFIT
	status	0	(Solution converged)
	variance	0.009513249
	stdeviation	0.09753589
	avsqerror	0.009510969
	averror		0.0975242
	avsqscatter	0.008489209
	avscatter	0.0921369
	chisqr		1.00024
	msq		0.00921596
	rms		0.09599979
	reference	mU
	fitting		(UB+BV+V)+u1+u2*XU+u3*BV+u4*UB*XU
	weights		photometric
	parameters	4
		u1	(fit)
		u2	(constant)
		u3	(constant)
		u4	(constant)
	derivatives	4
		0.1
		0.1
		0.1
		0.1
	values	4
		3.622
		0.552
		-0.15
		0.
	errors	4
		0.005
		0.
		0.
		0.