Problem with ASI 6200MM

freed

Hello, I image from a warm and not to humid climate. I cool down the ASI 6200MM camera to -8C. I cool down using my imaging software (voyager) very slowly - it takes at least 15mn. The problem I have is that I get these black donuts. They tend to disappear after 30 minutes. Anti-dew is on in ASCOM. See attached picture in link. The issue is only in the centre of the CMOS frame. Any suggestions on how to resolve this.
https://www.dropbox.com/s/bf4tdrh0ypkql0r/Problem_Preview01.jpg?dl=0
Thank you!

Tech@ZWO

Have you tried in ASIStudio? Is there same issue?

freed

Just tested this morning. With Dew on and temp at -8C using AsiStudio, I get exactly the same problem. What should I do ? Thank you

Tech@ZWO

freed
This is because the humidity is high inside the sensor and they are frozen on the sensor glass when the temperature drops quickly,

we recommend you slowly cooling the camera to solve the problem:

Before letting it cool down to target cooling temp, please keep it at 5℃ for 5-10 minutes, then cool it down to target temp and if this continues to appear, it will basically disappear in 5-6 minutes.

freed

Is it an alternative to try to dry up / open up the sensor / chamber? I have been in fact cooling down to 4C and waiting 15 mn before cooling to -8. Even at 4C I get these donuts. At -8C the last time they disappeared after 30 minutes which is really long.

wvreeven

freed Could there be an issue with anti-dew in ASCOM? I use an ASI6200MM as well. When I use it with INDI I get the donuts as well, because INDI doesn't have the anti-dew setting. With AAP I don't get any donuts at all.