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---1.03, 1.07, 1.14
Integration time (s)---1200, 900, 750750750750
Pixel scale (arcsec)---0.61, 0.61, 0.61

# Tue 14:29:26 14-May-2002
begin	UFIT
	status	0	(Solution converged)
	variance	0.01419573
	stdeviation	0.1191458
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.01419573
	msq		0.01242127
	rms		0.1114507
	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
		3.57078
		0.3969172
		-0.1194534
		0.
	errors	4
		0.08452704
		0.04432307
		0.03044868
		0.

# Tue 14:30:12 14-May-2002
begin	BFIT
	status	0	(Solution converged)
	variance	0.008268626
	stdeviation	0.09093199
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.008268626
	msq		0.00719011
	rms		0.08479451
	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
		1.744922
		0.2157
		0.05138599
		0.
	errors	4
		0.07610562
		0.03521893
		0.03280151
		0.

# Tue 14:33:00 14-May-2002
begin	VFIT
	status	0	(Solution converged)
	variance	0.02103762
	stdeviation	0.1450435
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.02103762
	msq		0.01941934
	rms		0.1393533
	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
		1.560629
		0.07103309
		0.03680699
		0.
	errors	4
		0.1002572
		0.04979341
		0.04291682
		0.