More Nexstar Madness - M35

[Smashtie]

I'm trying to get my Nexstar 8SE working with the f6.3 corrector and a new 2 inch visual back/clamp.

Some clear sky finally on 1st January, after weeks of bleh. So the attached is the first result - M35 and NGC2158. As usual, I'm on a low budget, with the original alt-az, unguided, 10 sec subs of which 35 were sufficiently stable. Now I'm using AstroArt 5 to stack, which takes out a lot of work compared to fitswork.

The 2 inch tube has removed a great deal of vignetting, which was the hope. I still see quite a lot of eggy shapes around the edges. Not sure if I should expect this given the size of my DSLR chip (Nikon D7000). Any ideas?