Matthew, Im astonished by the stars in that image... I assume with no focal reducer, you were running the system at F/10..
I've got a Lumicon OAG on the way for my C/11.. I was hoping that it will give me good results for 10 min subs at F/6.3... If you're able to get 15min at F/10 then I think I'll be very happy with my purchase!!
What mount are you running? G11??
Sorry for the off topic post...