ASI6200 Pro (monon) : Dew problem when cooling

astropixel

Hi,

Since this summer I use an ASI6200MM Pro (mono).
The ASI6200 is powered by a dedicaced 12 Volt alimentation 3A (constant) to 5A (surcharge).

This summer, I used -15°c or -20°c cooling (75% capacity) without any problem.
About a delta t of 30°c.

This winter, here in Belgium, the temperatures are cold (3°c).
I wanted to cool the camera down to -25°c (74%). But it is impossible.
I always have Dew that forms immediately, in the center of the sensor.

When I reduce the cooling down to -15°c, the dew disappears after 10 minutes.
Then, I can use the ASI without problem with a cooling of -20°c.
If I go to -25°c, dew is back!

I tried lowering the temperature step by step, slowly. As soon as I drop below -20°c, I have a dew problem.

Is this normal, is -20°c a limit?

For info, I see a difference in quality between the images taken at -15°c and -20°c. Being able to go down to -25°c seems justified to me.

I've uploaded some sample fit images, in the file :
https://drive.google.com/drive/folders/1yKBqGL2Wh8VvJUqsK00kayOwHgZCqMPi

Here is the session :

flat-20c-1842 : flat take @ -20°c : no problem
flat-25c-1854 : flat take @ -25°c : dew formation
flat-15c-1859 : 5 minutes later, Asi is @-15c : the dew is always here
flat-15c-1906 : 7 minutes later, ASI @ -15°c : all is fine.

Thanks for your help,

Sincerely

Sébastien Kersten

Tech@ZWO

Is Anti-Dew "On"?

astropixel

Yes, of course.

astropixel

Finally, is this normal or not? The camera is still under warranty, I prefer to know if I should worry or not.
Sincerely

Sébastien

Tech@ZWO

astropixel
It is possible to form dew when directly going down to a very low temperature(like -25°c). You can cool the sensor to much higher degree and wait for 10mins then set it to your target temperature.

astropixel

Hi,
That's exactly what I do. I go down in progressive steps.
@ -15°c I wait 10 - 15 minutes before I go @ -20°c
then, I wait 15 minutes before I go @ -25°c

Tech@ZWO

astropixel
-15°c is still a very low temperature, you can try 5°c.

astropixel

OK, but +5°c is higer of the outside temperature (+3°c) 😀
Next time I try per step of 5°c and i Come back.
Sincerely,
Sébastien

astropixel

Sorry to insist, but the problem is still there, and it's getting worse!

Tonight, the outside temperature is 3°C. Dew forms when the sensor is at -20°C (cooler power @ 58%)
I followed your procedure:

First set the temperature to 0°c (delta T outside only 3°)
Once I reached the temperature, I waited 10 minutes before moving on to the next step.
2 step : temperature @ -5°c. When ships @ -5c, waiting 10 minutes
3 step : temperature @ -10°c. When ships @ -5c, waiting 10 minutes
4 step : temperature @ -15°c. When ships @ -5c, waiting 10 minutes
5 step : temperature @ -20°c. When ships @ -5c, waiting 10 minutes

Of course, at each step I check in image.
Now @ -20c, I've a dew problem.

My camera is new and dates from August.
I don't think that's normal. What do you advise me to do?

Sincerely

Sébastien

Macobservatory

Did you ever solve this? I'm experiencing the same issue. No amount of temperature changes takes the dew away. I even tried at 30°C and still a dew ring right in the middle.

Macobservatory

I solved this issue tonight. It turns out that the dew left "residue" on the sensor glass, and no matter what temperature it remained until I took everything apart, and cleaned the glass, now it's good again.