here is a link to some 12" goto skywatcher dob shots i took some years ago when starting out.
https://www.flickr.com/photos/803366...57634243605994
https://www.flickr.com/photos/803366...57634238514125
i didn't really know what i was doing then, and am sure that i could get much better results. mostly these are only a few mins total exposure with no calibration frames except darks.
If you get flats, etc going and up the total exposures i can't see why you can't do way better.
there was a bit of a sweet spot in terms of the angle the scope was pointing (zenith is no good).
cheers
rusty