I have finished the objectives that I wanted for this script. Now it writes the result of the computation on the header of the FITS file. There are two checkboxes in the dialog. The first activates the writing of the keywords FOCALLEN, OBJCTRA, OBJCTDEC, XPIXSZ and YPIXSZ with the new values.
The other checkbox activates the writing of the referentiation of the image using the conventions specified in the papers that can be found at http://fits.gsfc.nasa.gov/fits_wcs.html
. The script generates the keywords CTYPEi, CRPIXi, CRVALi and CDi_j that define the world coordinates for the file. It also generates the keywords CDELTi and CROTAi that do the same but using an older and less precise convention.
The keywords should be compatible with Astromety.net and MaximDL with PinpointLE.
The script in its current state is reasonably accurate keeping in mind that it depends on the precision of the rendering and extraction of the stars of the catalog. A PCL module perhaps could bypass this process and use the coordinates of the catalog directly in the matching at StarAlignment.
Also, I have in mind an AnnotateImage script that overlaps a grid on the image and, if possible, the main objects (as Enzo suggested). This however would have to wait a bit.