One thing to remember Marty Omega has a number of blue straglers so look to revise your star colour IMO tracking etc appears spot on but what caused or is the dark patch at the bottom of the image ?
Thank you Trevor, in the full res pic it has plenty of blue stragglers.
still have to post the pics on photobucket.
The dark spot on the picture was a bit of dried moisture (gone now by using a lens pen).