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---1.40, 1.49, 1.42
Integration time (s)---1800, 1800, 900
Pixel scale (arcsec)---0.61, 0.61, 0.61

# Wed 16:27:43 15-May-2002
begin	BFIT
	status	0	(Solution converged)
	variance	0.002122746
	stdeviation	0.04607327
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.002122746
	msq		0.002037836
	rms		0.04514239
	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
		0.3216127
		0.061
		0.
	errors	4
		0.
		0.005664742
		0.
		0.

# Wed 16:28:32 15-May-2002
begin	VFIT
	status	0	(Solution converged)
	variance	0.002959888
	stdeviation	0.05440485
	avsqerror	1.
	averror		1.
	avsqscatter	0.
	avscatter	0.
	chisqr		0.002959888
	msq		0.002854177
	rms		0.0534245
	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
		0.2220432
		0.0075
		0.
	errors	4
		0.
		0.006431384
		0.
		0.

# Thu 15:53:28 11-Jul-2002
begin	UFIT
	status	0	(Solution converged)
	variance	0.002845645
	stdeviation	0.05334459
	avsqerror	0.002843805
	averror		0.05332734
	avsqscatter	0.0025803
	avscatter	0.05079666
	chisqr		1.000647
	msq		0.002731819
	rms		0.05226681
	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
		0.465
		-0.15
		0.
	errors	4
		0.005
		0.
		0.
		0.