Beautiful lunar image and a very impressive start to deep-sky astrophotography. I think that a reflector like yours is a great place to start as you're not going to have chromatic aberration to worry about, which stumps everyone with a cheap refractor.
To try answering your question. I'd definitely try capturing a movie of the moon and then using Registax
http://www.astronomie.be/registax/ to create a single image. Look up tutorials for it though on youtube cause it has a steep learning curve IMO.
As far as your Lagoon image goes, it's really quite superb for a first go at deep-sky work. Your focus is very good, which is much of the battle. Longer subs are always good but try capturing 10, 30, 50 or more shots and stacking them, you'll see the extra detail starting to come out.
You'll also want to take some flats. Point your scope at your computer monitor set to white and image this 10 times with an exposure long enough to get the histogram peak roughly mid-way. Then puts those images into DSS as flats and you'll be able to correct for the vignetting at the edges of the frame, as well as dust and crud. If you can't image your computer screen like this, then try a twilight sky. If the result has some stars in it then just Gaussian-blur them out.
Hope this helps,
Cam
Then you can go much deeper with longer subs and more of them.
