CCD Stack - Missing Values

Frank Puzycki

I purchased a larger apo refractor recently and decided to attempt another composite M31 image using missing values construct per Adam's tutorial.  I shot 35 3 minute subs at 180" and a like number of subs at 15".  I processed each stack using CCD Stk and then refined both images using Photoshop extended plus a few plugs ins.  I normalized both images with the 180" image on top.  The resulting weights approximated the exposure ratio.  I used 40,000 to 100,000 to create the missing values range.  I also did a 5 pixel grow but whne I finally did the combine operation, the nucleus area was distinctly brighter than the abutting area at 180".  Should I have not  processed the two images through PS CS6 extended before running the missing values construct?  I tried  to up the minimum value restrict range to 45000 and 55,000 but that failed to remedy the mismatch.  Any thoughts would be welcome.

Frank P.

BlockHead

Sorry..I am not certain what you are doing. But I think the answer is yes... you need to leave the images 100% linear. This is a linear fit and the "refining" you mention probably messes this up.

-the Blockhead