Modified photred_astrom.pro to use the combined image as the astrometric reference frame.  In the original combination scheme the reference image and the combined image had the identical WCS.  In the new scheme they are very different but the combined image is the "reference frame".
Modified photred_astrom.pro to use the combined image as the astrometric
reference frame.  In the original combination scheme the reference image
and the combined image had the identical WCS.  In the new scheme they
are very different but the combined image is the "reference frame".

dnidever/PHOTRED,dnidever/PHOTRED