ASI294MCPRo fog in center of camera

[vcouleh]

I am experiencing what looks like fogging - IU have changed and checked the  desiccant I also installed dew heater on the camera from ASI  see the attached photo 

 

Thanks

[michael8554]

Apologies for stating the obvious, but Flats without cooling are okay ?

Michael

[Xilman]

6 minutes ago, michael8554 said:

Apologies for stating the obvious, but Flats without cooling are okay ?

Michael

You will have the thermal noise in your flats, so either take many more of them and average, or accept noisy science images.

Not a good idea, IMO.

[michael8554]

Did you really think I meant he should always run without cooling ......... ?

Is the problem really due to fogging ?

A single Flat taken  WITHOUT COOLING will show whether it's fogging or not.

Geddit ?

Michael

 

[vlaiv]

27 minutes ago, Xilman said:

You will have the thermal noise in your flats, so either take many more of them and average, or accept noisy science images.

Not a good idea, IMO.

How bad can it actually be?

Flat exposures are very short, even if there is significant amount of dark current - signal will simply be stronger.

ASI294 has less than 0.5e/px/s for 25° sensor temperature. Even if we double that one or two times - we are still much lower than shot noise per sub if sub is taken at say 60-75% FWC which is 63.7K. Even with higher gain, if FWC is reduced to say 4K, shot noise is still like 20-30 larger than dark current noise so contribution of dark current noise is negligible for flats here.

[vlaiv]

On 22/11/2021 at 20:38, vcouleh said:

I am experiencing what looks like fogging - IU have changed and checked the  desiccant I also installed dew heater on the camera from ASI  see the attached photo 

What software are you using for flats? What is your offset set to. Did you calibrate your flat in any way? What does the raw flat sub look like.

In fact - can you upload one for inspection?

Sometimes there is some sort of clipping that will produce weird artifacts on flats. If you are using software flat assistant - try shooting flats manually / manually setting exposure time and manually calibrating it to see if there is difference.