Nice to see a wide field galaxy shot, good effort
I wouldn't consider the subject a hard target for the scope, but combining the scope with an un-modded DSLR it gets tricky
Could you push your exposures out to 10 mins? If it were me I think I'd have gone for half the number at 10 mins. But Depends on many factors that only the photographer can judge
It looks like you have some kind of issue with your darks, shown by the "dark rain" in the background (trailing dark pixels). With my DSLR I usually get this when dark frames are correctly matched to the light frames (usually by way of different chip temperature).
It looks like you could improve it by removing a gradient also, brighter at the bottom than at the top.