Your image isn't perfect but i sill like it
looks clear and clean and not over processed something that i tend to do.
Though for such a bright target it is a little dark.
I'm sorry i cant help you with tips on using your DSLR as i have no experience at all in using them.(i went straight to ccd)
Your stars do seem to be trailing in one direction a little suggesting tracking errors perhaps.
Check ensure the scope is well balanced in Ra and Dec.
Check your cables for guide scope make sure there is no cabble tension pulling on your gear.
We don't know how good your polar alignment is would help if you took a screen shoot of your PHD graph.
Perhaps you could try a different approach to polar alignment i use alignmaster works perfect for me.
If your using a stock standard focuser you could possibly improve thing allot by forking out for something decent like a moonlight.