Noise on sensor when cooled to max ZWO ASI294MC Pro · Niels_L · ... · 6 · 159 · 3

Niels_L 2.39
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The outside temperature is currently 29.9C (yes, I am in summer) and I am cooling the camera to -10C as I normally do.  I've seen this noise a few times in the centre of the sensor but never paid much attention to it as it disappeared (guess the outside temperature dropped).  I did now notice it comes up when the sensor goes below around 1C and gets worse the lower the cooling goes. I guess I am getting to the max of the cooling? I take it this is then noise from the cooling electronics?  
With temperatures changing throughout the night, it would be impossible to take flats at each temperature. At these high temperatures, should I then increase the sensor temperature to 5C?

Quick side temperature, do darks need to be taken at a specific sensor temperature?

Below is an example of one of the flats at -6C with a STF. First is full flat image, second zoomed in somewhat, third on pixel scale.

Full image:
Screenshot 2025-02-23 at 20.48.29.png

Zoomed in:
Screenshot 2025-02-23 at 20.48.45.png

Pixel scale zoom:
Screenshot 2025-02-23 at 20.48.50.png
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frankz 4.07
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That’s not noise, IMO. It’s ice crystals. Try cooling a bit more slowly. If it doesn’t help, you may need to think about replacing the desiccant tablets in the sensor chamber.
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HegAstro 14.24
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Ice crystals, not noise. It will usually go away with time, or you can cool it above freezing.
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frankz 4.07
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Ditto what Arun H said about cooling temperature. I cool my 294MM at 0C, the difference compared to -10C is minimal and I don’t need to worry about ice.
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j_paul 2.11
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There's no need to cool so deeply. the 2600, only has a delta-T of 35c. You're cooling power would be maxed out, and tha'ts a good way to unnecessarily stress the electronics.

The idea behind sensor cooling is to get a stable temperature, not the absolute lowest. Your darks should be taken at the same settings as the lights frames you're matching them to - Exposure time
Gain
Offset
Binning
Temperature.

I can comfortably image at 0c all year round. my winter lows are around 5c.
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Niels_L 2.39
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Arun H:
Ice crystals


Interesting!  Indeed, it seems to apprear around the 0C.  I decided to run tonight at 5C as 0C is on the edge for the ice...
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HegAstro 14.24
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Arun H:
Ice crystals


Interesting!  Indeed, it seems to apprear around the 0C.  I decided to run tonight at 5C as 0C is on the edge for the ice...

during summer, I took to cooling to 1 C for that reason and the problem went away. Pretty sure cooling to 5C will work for you. Let us know how it turns out.
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