I wish my first go had looked that good.
If you have a mac, try nebulosity out and see if you like it. You can try before you buy, and it is cross-platform.
It is a great starter program.
http://www.stark-labs.com/nebulosity.html
Some other useful apps there as well.
There is also StarTools which I am just learning now, it looks good so far.
http://startools.org/drupal/
The image looks a bit overprocessed, a bit heavy on saturation and sharpening, but a cracker of a result for a first go. You will be able to bring the noise down a bit with the stacking and pull some more detail out.
A 7.5 means long exposures, might look into a reducer for that scope.
What was it mounted on?
I'd go to ISO 800 on the D700.