STARFIT

Name

starfit

Purpose

Single gaussian fit to a stellar image.

Description

Fit the equation y=f(i) where:
X = I MOD NX
Y = I / NX
R = SQRT( (X-A0)^2 + (Y-A1)^2 )
Z = R/A3
F(I) = A2*EXP(-Z^2/2) +
A4 + A5*X + A6*Y + A7*X^2 + A8*Y^2
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
A4 = Constant term for the background, 0
A5 = Linear term in X for the background, 0
A6 = Linear term in Y for the background, 0
A7 = Quadratic term in X for the background, 0
A8 = Quadratic term in Y for the background, 0

Calling Sequence

starfit, image, guess, model, a, sigmaa

Inputs

image - Input image to be fitted, must be 2-d.
guess - Input information for starting guess.
guess = estimate of the 1/e full width of the seeing.

Outputs

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

Optional Output Parameters

Common Blocks

starfit_com - contains the xwidth of the image.

Side Effects

None.

Restrictions

Procedure

Modification History

Written by Marc W. Buie, Lowell Obs., 1993 January 13.