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mpfit2dpeak and chi-square [message #46030] Tue, 25 October 2005 07:44
JJMeyers2 is currently offline  JJMeyers2
Messages: 12
Registered: October 2005
Junior Member
Hello,

I am trying to use mpfit2dpeak and I am trying to understand the result
that comes out of chi-square, so I was wondering if someone can help me
out. I am describing the problem.
I have an image with random star positions x,y (the image has 2048x2048
pixels). I am trying to fit the positions to a 2-d gaussian. I have a
vague idea where the central density of the stars should be and I
create a square of 400x400pixels around it and I calculate the density
of different circles in this square in order to fit it to a gaussian.
After running mpfit2dpeak the results I get for the gaussian parameters
and the errors are reasonable. When I use the keyword CHISQ though I
get a very big number (245781 which divided by 160000 is 1.5) which is
very big and is not reasonable since the errors are very small and the
fit looks very good. I was wondering if I am using the chisq in a wrong
way and the result that I get is not what I think it is.
Any suggestions?

Thank you,
Jim Meyers

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