NAME:
	plchfit

 PURPOSE:
	Two gaussian fit to an image of the Pluto-Charon system.

 DESCRIPTION:
 	Fit the equation y=f(i) where:

		X  = I MOD NX
		Y  = I / NX

		R1 = SQRT( (X-A0)^2 + (Y-A1)^2 )
		R2 = SQRT( (X-A9)^2 + (Y-A10)^2 )

		Z1 = R1/A3
		Z2 = R2/A3

 		F(I) = A2*EXP(-Z1^2/2) + A5*EXP(-Z2^2/2) +A4

	Function parameters				Initial guess
       --------------------------------------------    --------------------
	A0  = X location of center of Pluto,		Maximum in image
	A1  = Y location of center of Pluto,		Maximum in image
	A2  = height of gaussian for Pluto,		Max - Min from image
	A3  = the 1/e width of the guassian,		GUESS(0)
	A4  = Constant term for the background,		0
	A5  = height of gaussian for Charon,		A2/7
	A6  = X location of center of Charon,		A0 + GUESS(1)
	A7  = Y location of center of Charon,		A1 + GUESS(2)

 CATEGORY:
	Function fitting

 CALLING SEQUENCE:
	plchfit,i,y,numx,guess,model,a,sigmaa

 INPUTS:
	image  - Input image to be fitted, must be 2-d.
	guess  - Input information for starting guess.
		  guess(0) = estimate of the 1/e full width of the seeing.
		  guess(1) = X offset of Charon relative to Pluto.
		  guess(2) = Y offset of Charon relative to Pluto.

 OUTPUTS:
	model  - The fitted model image is returned.
	a      - The final coefficient array.
	sigmaa - The uncertainties on the coefficients.

 OPTIONAL OUTPUT PARAMETERS:

 COMMON BLOCKS:
	plchfit_com - contains the xwidth of the image.

 SIDE EFFECTS:
	None.

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
	Written by Marc W. Buie, Lowell Obs., 1993 January 13.
	93/07/01, MWB, Converted to new fitting function protocol.