My goal here is capturing detail in galaxies at a modest focal length. I have an 11" RASA on the way, which has a focal length of 620mm. Looking at the 11" RASA, the specs are a Dawes limit of 0.42" and Rayleigh limit of 0.49". Supposedly, unlike Hyperstar setup, the RASA might be diffraction limited, according to Celestron catalog I had it said "43.3 mm optimized image circle (with a 52 mm useable field) maintains diffraction limited, pinpoint stars to the far corners of even the largest astroimaging sensors". Though maybe this is not the case as I see they no longer have the "diffraction limited" line on their product website now.
Both cameras would produce an image scale of 0.8"/pixel. I am hoping to do short exposures in the range of 5 second or less to overcome seeing effects which I think should work well with RASA.
I have been looking at these two sensors, trying to distinguish any difference besides the obvious one - sensor size. Both are small and should fit most galaxies fine, but to summarize, the differences are:
Sensor Size 7.4mm x 5mm 13.2mm x 8.8mm
QE% Peak 81% 84%
ADC 14 bit 12 bit
Read Noise (HG-LG) 1.4e - 2.4e 1.6e - 3e
Both are BSI, both have 2.4um pixels, and both have a maximum 15K fullwell. The 183 is approximately $250 more than the 178 for a cooled version, $300 more for uncooled (which may be an option if I just do short exposure).
Has anyone had any experience with either of these on a RASA or Hyperstar themselves? Or any comparison between the two at all on any scope. I know I've seen Mark Holbrook's incredible galaxy images with the 178 and 183 with a 14" Hyperstar setup which has a 690mm focal length which has been the inspiration here, but that is the pinnacle of greatness, so looking for more experiences. I guess my key questions are just wondering if the extra cost of the 183 is worth it over the 178 for a bit bigger FOV, or if the 14 bit ADC of the 178 puts it ahead a little bit in terms of dynamic range.
I currently have a QHY5III178M (uncooled version I use as a guide camera), which I plan to test out to begin with to see how this goes before buying anything else once I get it...but that brings up another concern, there is kind of an odd diffraction pattern on brighter stars that I do not like, though I did not see that on Mark's images with it.