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.