Unfortunately you are hitting an "equipment spec wall" that is pretty hard to breach.
I had a good look at your full res image that can be found via here
http://www.celticcomputers.com.au/As...up&cat=0&pos=0
This is a tough target for a DSLR/CMOS. While they are excellent tools for wide field/ bright object imaging, dark objects in less than pristine skies are very difficult to capture well.
http://panther-observatory.com/galle...C2359_c100.htm
is a great example of a better tool for the job....
The cynics may cry "Sure, there is always a bigger fish!" but this is not the point of my response.
Sometimes it really is a case of "don't force it...simply use a bigger hammer"