Since I want to use Siril to calculate FWHM in my Bachelors thesis I wanted to find out how Siril fits the gaussian function around a star. I looked at the source code, but I am not well versed in c so I can’t quite make sense of it and it does not quite resemble the way I know of how to fit gaussian functions to measure star FWHM as far as I can tell.

G(x,y)=B+A*exp( −((x−xi)^2 +(y−yi)^2) /2*σ^2) this is the formula I know of, but the form used in the source code seems to have a slightly different form.

I would just need the basic gaussian function the software uses, so I can put it in my thesis. Thank you!