Atik 383L+ - unexpected noise problem

[vladutz]

Hello
First off, I'm writing this for a friend who recently bought a new 383.
This is the second camera - the first one was changed by his Spanish dealer within days because one of the screws that hold the sensor level fell off!

This second camera seems to be ok, but the last couple of times he used it, it showed some unexpected behaviour. Images started looking noisy, as if the cooling had gone off, then after a few shots it would go back again to normal. We have observed this over two nights, in ideal weather conditions. The temperature control did not move away from -20C, at least according to the software, but the deterioration in quality is obvious, as can be seen in the attached picture. (left-clean, right-with noise).
Before we go back to the dealer to change it again, he would like to know if there are any other possible causes for this, outside of the camera.
Thanks!

[vladutz]

Ps - better quality fits files also available, should they be required.

[bwa]

Most obvious reason for problem is failure of the cooling system.  It will definitely have this type of impact on subs...

Maybe that 383 was built late Friday afternoon before a long weekend??

bwa

[vladutz]

that was my first thought, however, the temperature never moved from -20C in all this time - so unless the temperature sensor was lying, I believe the temperature was that shown.

[vladutz]

A further picture to better show what the problem is.
This one is from 2 nights ago..

[Chris]

It's not thin cloud is it? Or some sort of outside light?

It would be worth checking dark frames.  If the camera is adding noise, such as the cooling not working, then this will show in the dark frames.

Chris

[Steve]

Hello,
This does look a bit of high cloud in the second image.  If the camera is reporting -20 its because the camera is at -20.  No trickery!
You are welcome to send the fits into support@atik-cameras.com if you would like us to take a closer look.
Best
Steve

[vladutz]

I have sent you fits to the provided email address.

The high clouds were our first guess too, however,  on this occasion, we had two cameras mounted side-by-side on the same mount and only this one showed this noise. Sky Quality Meter kept constant at 20.86