Precise centroid calculation and WCS-SIP fitting

[Rafael Morales Muñoz]

Dear all,

I am interested in the precise centroid calculation of image sources. I 
have tried to find information about how it is calculated in GNU-Astro. 
Maybe it is my fault, but I cannot find any clues in the documentation 
or implementation.

I am also working on the WCS-SIP fitting of an image using a star 
catalog. Once again, I could not find relevant information.

Could you please guide me on where I can find more details about these 
issues?

Regards,
Rafael