The image below is of the Ring Nebula. I was surprised to see that after stacking the hole in the middle of the Ring was blown out (over saturated?).
I took rather short exposures of 120s with a IDAS NBZ filter (during a full moon but in the opposite side of the sky). I used an ASI533MC-P with my Orion 8" Newt. Should I have taken shorter exposures - maybe 60s?
I only stacked 83 subs because something happened in the middle of the night and my tracking failed for the other 67 subs - so I had to throw them out (the stars were oval and some subs showed trails). The 83 subs I used were in good shape with decently round stars.
The first pic is the stacked image and the second pic is an individual sub in which you can still see the hole. Any idea what I did wrong?