[The_bluester (Paul)]

OK, I will pose a question, what term would you use to define the difference between the smallest and largest recordable signals for the system? I will add that I don't really care what you want to call what I am measuring here. In the context of my original post it is about as relevant as an ex workmate of mine who went to work for NBN and started telling people that they should not voice their opinion if they did not know that the NBN box on the wall was a "Network Terminating Device" not a "Network Terminating Unit"



From my own data and Colins post here regards the 14 bit data value being multiplied by 4 for use in the 16 bit fit files I can show that the useful range of the camera as a system at just above unity gain, where the noise profile improves markedly (And I can tell you, visibly) is approximately one quarter of the full well depth of the sensor, ignoring noise and dark current for simplicity. An area of a 30 second sub I have yields an ADU off the sensor of approx 3500 (Divide the 16 bit by four) Again ignoring dark current and noise, a 300 second sub (Which was shot right after the 30 second one) would yield about half of the full well depth, call it 35,000. except from around 150 seconds exposure time the feature in question will hit the conversion limit at unity gain and that is that, though the sensor will go on accumulating electrons.



Given that the noise profile improves so much around unity gain and that the output effectively saturates at about a quarter of the sensors range I would argue that it is demonstrable that the 14 bit conversion is a limiting factor for astro use, and a symptom of that appears to be saturated and relatively colourless stars that are the reason for my OP. And note that I have never said that Sony "Wasted" dynamic range by designing it with 14 bit conversion or that they don't know what they are doing, they did not design the chip for this application and for that we can be thankful as it means there are cameras out there that people can actually afford that produce some pretty good results.


Again, I don't care what anyone else wants to buy, if they make a camera with 100,000e wells and 12 bit ADC and people want to buy it that is up to them if it has some compelling selling point. I won't be buying a new camera for this purpose in future unless the ADU count meets or exceeds the pixel depth as it is one less compromise to consider, in the mean time I will understand where the ASI294's limitations are and work within them, the known flat fielding and uneven cooling issues are one, this is another.