OK.. here's the challenge: Barnard's Loop: Your DSLR vs my little Panasonic LX5. Single frame only, no stacking.
Prizes ? Hmm... Only the glory of the best image.
I have a slide taken 30 years ago from Mt Bowen, on Ektachrome 200 with a Pentax SLR with 50mm f/1.7 that captured Barnards Loop very nicely in a 15 minute exposure. With the latest firmware I suspect Barnards Loop is just within the grasp of the LX5 - without a tracking mount, just a fixed tripod. With the LX5 my maximum exposure is 4 minutes at f/2. For the lens, I'll shoot at either 17mm or 24mm (35mm equivalent) at f/2.
I'll stay silent on the question of ISO, my answer will probably be a big surprise.
You have a tracking mount and a DSLR with a far bigger sensor (less noise) but a slower lens, so it should be reasonably easy for you.
PS Take your time. The weather in Sydney has been utter crap for weeks, so it will be next year before I get a chance in dark skies without the moon.
PPS re the LX5 vs your DLSR. In case you are laughing yourself silly, note these two are SHORT exposures taken on holidays when i wan't even trying seriously...
http://www.dpreview.com/galleries/73...-cook-airstrip
http://www.dpreview.com/galleries/73...k-by-moonlight