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What is the best way to cool down camera in hot and humid nights?

Dew Heater CMOS Acquisition Deep Sky
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Yuxuan avatar
Yuxuan avatar
I've tried different desiccants, and I've tried running several cooldown and warmup cycles, but oftentimes in Florida at this season I still lose a few hours per night waiting for dew on my sensor to disappear. 

My question is what the best strategy is from your experience. Should I give up cooling it down to -10C? Should I try a different camera than my ASI6200MM?
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Bill McLaughlin avatar
Bill McLaughlin avatar
If you mean dew on the actual sensor (as opposed to the camera window) the best would be to use a camera with a beefy replaceable desiccant and enhanced cooling such as a Moravian. I would also say that for the QSI -5 is OK as well.
Sean Mc avatar
Sean Mc avatar
Does the 6200 have a dew heater?  Or does ASI sell one for that camera?
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Yuxuan avatar
Yuxuan avatar
Sean Mc:
Does the 6200 have a dew heater?  Or does ASI sell one for that camera?

The dew heater only heats up the optical window, but the condensation is on the sensor itself.
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Yuxuan avatar
Yuxuan avatar
Bill McLaughlin:
If you mean dew on the actual sensor (as opposed to the camera window) the best would be to use a camera with a beefy replaceable desiccant and enhanced cooling such as a Moravian. I would also say that for the QSI -5 is OK as well.

Thanks, I probably will need to raise the temperature.
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Francesco Meschia avatar
Francesco Meschia avatar
Cool slowly, and cool less. Unless you're doing really, really long subs, there is no reason to cool below 0C. According to the data published by ZWO, the difference in dark signal between -10C and 0C is 0.00146 electrons per pixel per second. And dark noise is the square root of signal. Even with a 20 minute sub, you'd be adding only 1.3 electrons of noise per pixel at 0C compared to -10C.
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Chris White- Overcast Observatory avatar
Chris White- Overcast Observatory avatar
I have the same issue in my location.  The answer is to not cool as much.  In the summer I only cool to 0 degrees C.  While thermal noise is lessened with further fooling, the benefits are marginal.  These IMX*** sensors are really low noise… I cant tell any difference between 0 and -10.  During the winter I cool much more, but that is because my ambient temp can be as low as -20C.
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Bruce Donzanti avatar
Bruce Donzanti avatar
Same for me, as Chris.  I am living in Fl and image during the hot/humid summer, using both the ASI6200 and ASI2600.  Both cameras work fine when set at 0 degrees.  Any dew will dissipate within about 45 minutes.  Frankly, you will be hard pressed to reach -5 degrees without reaching 100% power use. There is virtually no noticeable difference between 0 and - 10.  In the fall/winter I still use -10.  
I’ve heard too many horror stories about trying to replace the desiccant pellets in the 6200.  So, I just set the camera to 0 degrees and wait for any dew to dissipate.
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TiffsAndAstro avatar
TiffsAndAstro avatar
I just cool my imx533 to -5c

Imx sensors seem to double their noise every  5 degrees, but two times not very much is still not very much smile
nikolashodges avatar
nikolashodges avatar
slowly I would say
Yuxuan avatar
Yuxuan avatar
Thanks everyone, I will only cool to 0C going forward!
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Mark Petersen avatar
Mark Petersen avatar
I have a 6200mm pro and have noticed the same thing.  This is my workaround - As part of my normal startup I cool to 2C and let it stay there for at least 5' before going to -10C.  The idea is that at 2C, the moisture will freeze out at the coldest part of the chip (which is away from the window which is presumably above 0C), and then once the moisture has frozen out, it is safe to go to -10C.   I tested this by capturing images exposed via a flat panel.  If you zoom in, the frozen droplets appear as tiny black dots on the image.  Repeatedly warming and cooling the camera while capturing images in a loop makes the issue pretty easy to see and was also how I tested the mitigation step above and how I figured out how long to stay at 2C.  This has been working well for me, but this is the sort of thing that will vary for everyone based on how well their camera is sealed.
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