This is a SINGLE, unstacked 20 sec exposure at ISO 1250 of M 42, using a Vixen VC200L at f/6.3 and a Canon 5DMkII (unmodified).
More clarity and colour than stacking the other 40 subs
Hmmmmm...
Might whack it into MaxIm DL and see what happens.
EDIT: second picture is 40 subs of 20" / ISO 1250 stacked, with someprocessing. A bit of a difference! (if only the focus was spot on!)
Shame it's a jpeg... looks MUCH better in PS than the compressed version here
