nice work Graeme,
its possible to push the SW goto dobs out to 25-30 seconds. I used to image using iso 3200 and 20 second exposures with my 12" goto. you should be able to get similar results with your setup.
https://www.flickr.com/photos/803366...ream/lightbox/
https://www.flickr.com/photos/803366...ream/lightbox/
https://www.flickr.com/photos/803366...ream/lightbox/
https://www.flickr.com/photos/803366...ream/lightbox/
cheers
Rusty