Nice shot of M31
I'm doing the same as you except for the longer exposure times (My HEQ5 controller failed so only could do short exposures this year) I use Nebulousity for stacking and stretching the image them use photoshop CS5, I find a useful tool in the menu Image-Adjustments-Shadows/Highlights. Tick 'Show more options' try using it after levels and curves. Hope this helps
