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PLCHFIT

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)

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.

Common Blocks

plchfit_com - contains the xwidth of the image.

None.

Modification History

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

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