Thanks for the excellent write up. Much appreciated. I guess one of the things that I did want to find out was, are we, getting our money's worth by using "fast" systems with small pixel CMOS cameras.
Going by experience, I have received some data from a friend who is in the process of automating their 27in scope (believe it is F6, so not necessarily the slowest that's out there, but not that "fast" as well, with around 4100mm FL). They are using a 16803 chip camera and the data that I received, was around 5 hours (LRGB), was simply stunning. I could not believe the amount of detail that I was viewing in that image.
That got me thinking around why is it that telescope manufacturers are pushing for fast systems? The real question was, are we sacrificing quality in a bid to lower costs? But I suppose there is no clear answer to this - it seems that manufacturers want to drive the cost down (which is great), but it also sounds like there is not a whole lot of degradation from a quality standpoint (based on your reading, which is also great). I am hoping that is true and remains so!
I suspect that a 27" f/6 (PlaneWave CDK?) would certainly be of higher optical quality than something like an ONTC Newt from Teleskop Service. The TS mirrors seem to be fairly good, better than the general consumer-grade GSO mirrors, but I doubt they are of the same caliber as an ion-milled mirror. That said, you CAN get some very good newtonian astrographs with very high end mirrors. I've read about some with 1/10th wave (and even better, but you have to phone in the orders so I don't know how much better you can go). The scopes are again pricey, but if you want the quality in the optics, and also want the scope to be fast, it is possible to get both.
Camera-wise, a KAF-16803 has the edge when it comes to dynamic range and has a 16-bit ADC. It is difficult to clip stars with it, even with very long exposures (at around 4000mm FL it is possible to get 20 minute LRGB subs with minor clipping!) Data quality wise, I am not sure that the out-of-camera performance is really all that great. I've seen some very clean 16803 data, as well as some pretty darn dirty 16803 data. Column defects on such a large chip are not uncommon, and it also seems it can have amp glow in one corner.
The IMX183 has some strong amp glows, strong enough that it does introduce a small amount of additional shot noise in those areas of the frame. However it seems to calibrate out fine. From a calibrated sub standpoint, my personal experience is the KAF-16803 and IMX183 data is on par. The 16803 usually has some remnant column defects and sometimes a bit of remnant glow, the IMX183 sometimes has some slight random horizontal banding. In both cases, cosmetic correction will correct most of the remnant FPN, and stacking averages out the remaining random noise.
The bigger differences between current generation CMOS cameras and long-established CCD cameras are going to be things like reliability, robustness, longevity. CMOS cameras have only been around for a couple of years. CCD cameras have been around for decades, and some have even resided in remote observatories, unattended to, and operated for a decade or more in some cases. There are certainly issues and failures with CCD cameras, but overall they have a pretty good track record of being reliable for long term remote operation. That cannot be said about CMOS cameras yet, so if you NEED high reliability and robustness, and NEED very high grade optical quality, then those are certainly reasons to consider the much more expensive, larger systems. However, if you want good IQ at a lower price, then I think it can certainly be attained with some of the current generation CMOS cameras...and at significantly lower cost. (Lower cost not just because of the camera, but because you can get smaller scopes, which overall lead to lower weight, which is less demanding on focuser and mount, so the whole entire system can shrink.)