The hyperstar is doing most of the work, I have one on a C14, and the performance is incredible at f1.9
The A7S is a pretty nice DSLR, especially for time lapse work, but for Hyperstar use I think you are still better off with a 'can' shaped, cooled CCD. You are looking at over AUD$3000 for a modified Sony DSLR landed in Aus, that can get you a pretty nice 2nd hand CCD.
I'm looking forward to Sony's rumoured new sensor tech...
http://www.gizmodo.com.au/2014/11/le...future-cameras