Nice one
What is the focal length you are running at? By the looks of the field, I am guessing it's 18mm. With that focal length and camera your maximum shutter speed should be about 20 seconds according to the 600 Rule of fixed tripod astrophotography (600 divided by the TRUE focal length of the lens(need to multiply by any crop factor)= max shutter speed before stars begin to move too much) For even tighter stars I would use 500 instead of 600.
Of course this is going to limit the detail you will be getting in each sub but I also own a 60D and know from personal experience that it can easily hit higher ISO's without too much more noise. Because you are also stacking the frames any noise gets reduced anyway. So next time I would suggest a shutter speed around 15-20 seconds and ISO 3200 and you should get much better data to play with and the stars should be a lot tighter.
Hope this helps.
Cheers
Greg