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---1.25, 1.44, 1.28
Integration time (s)---1800, 600, 600
Pixel scale (arcsec)---1.134, 2.31, 2.31

# Mon 14:18:27 13-May-2002
begin	BFIT
	status	0	(Solution converged)
	variance	0.005792269
	stdeviation	0.07610696
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.005792269
	msq		0.005605422
	rms		0.07486936
	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
		4.198739
		0.3198709
		0.05321241
		0.
	errors	4
		0.07691998
		0.05624191
		0.01461287
		0.

# Mon 14:26:59 13-May-2002
begin	VFIT
	status	0	(Solution converged)
	variance	8.763281E-4
	stdeviation	0.02960284
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		8.763281E-4
	msq		8.467890E-4
	rms		0.02909964
	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
		4.023283
		0.1690694
		0.006677317
		0.
	errors	4
		0.02940393
		0.02125077
		0.005778548
		0.

# Thu 11:51:13 11-Jul-2002
begin	UFIT
	status	0	(Solution converged)
	variance	0.002407606
	stdeviation	0.04906736
	avsqerror	0.002406685
	averror		0.04905798
	avsqscatter	0.001459845
	avscatter	0.03820792
	chisqr		1.000382
	msq		0.002360398
	rms		0.04858392
	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
		5.251
		0.459
		-0.121
		0.
	errors	4
		0.003
		0.
		0.
		0.