[The_bluester (Paul)]

Just looking to check my thinking, I was actually considering posing this question to ZWO.

My ASI294MC Pro has 65K (Approx) pixel wells. It also has a 14 bit ADC. That means approx 16K output levels.

I have been working to improve my star colours for a while. They have a tendency for the brighter stars to look blown out and white even at relatively mild stretches.

I was looking at the ADC specs and I wonder if anyone else would share my thinking. At unity gain (Which approximates 1 electron = 1 ADC count) any pixel well over approx 16K electrons will be effectively saturated as the ADC has no more to give? The output files still show 65K levels, so I am assuming some multiplication factor is at play in the camera firmware to expand the output range to match the pixel well depth. It is irrelevant though it 65K output actually equals 16K off the ADC.

The way I am seeing it, to get much better results I need to layer in shorter subs for stars and bright areas to keep them from hitting more than 16K and effectively saturating as while I can spread the dynamic range by reducing gain, the data becomes non linear as more than one electron is required to change the output of the ADC, up to 4 in fact.

The gain setting looks to me to be something that is masking an ADC that really needed to be 16 bit to begin with, the ASI1600 would be even worse with 12 bit ADC, it sort of explains why they seem to produce great results out of short subs, anything longer and the output effectively saturates.

Should I just grit my teeth and save up for a 16 bit camera like the coming ASI2600? I actually have my eye on those ones but I will be letting others take the plunge first to see if they have cooling or flat fielding issues like my 294. An ADC that can cover the entire well depth of the pixels would be a pretty big advantage as I see it.

Anyone reckon I am just flat wrong in thinking that they have to be effectively wasting a lot of the sensor dynamic range on cameras like the ASI294MC with a 14 bit ADC?