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For astrophotography using 'medium size' land telescope at good location,

  1. How many time longer exposure, in view of boosting the system's ability to photograph even darker objects, can one gets from cooling down digital camera sensor chip?

  2. Is there a 'sweet spot' temperature where most thermal related noise is suppressed and further lowering of temperature yields litter extra benefit.

  3. What is the ball park temperature for low (amateur), medium and high (professional) grade cooled camera?

Web search shows that Peltier electric cooled camera works at around "minus a few tens degrees centigrade". Does the really professional one cool to more extreme level, somewhere close to liquid nitrogen temperature?

  1. Does CCD, CMOS or other sensor have different 'sweet spots' temperature?
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  • $\begingroup$ Depends a lot on the chip. $\endgroup$ – Carl Witthoft Jun 1 '17 at 13:02
  • $\begingroup$ The real question would be what kind of cooling are you talking about? piezoelectric, air based or compressed gas? $\endgroup$ – Spilt_Blood Jun 2 '17 at 14:31
  • $\begingroup$ Web search shows many amateur use CMOS system works at, says, minus 30 centigrade (or any way to say the same as 45 centigrade below ambient temperature). $\endgroup$ – EEd Jun 7 '17 at 3:00
  • $\begingroup$ Web search shows many amateur and mobile use CMOS system works at, says, minus 30 centigrade (or any way to say the same as 45 centigrade below ambient temperature). What exposure time for these mobile system, funded by amateur people? Does professional unit that are inside fixed observatory building, presumably, camera is just a small percent of the whole building with telescopes, they having more money to spent on camera, what type of camera they use and what cooling, what exposure time can these best state of the art system get? $\endgroup$ – EEd Jun 7 '17 at 3:06
  • $\begingroup$ What exposure time space telescope use? Camera and electronic driver cooling is done automatically $\endgroup$ – EEd Jun 7 '17 at 3:09
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The practical length of the time exposure will depend on your equipment. Cameras used in astrophotography are generally able to be used with exposure times ranging from milliseconds to hours. As your question stands, cooling the chip will have no effect on the length of the exposure time. What it can affect is the amount of noise in the image. Cooling the sensor generally reduces the amount of noise. Cooling beyond -20°C may have limited value, particularly if you are not using research-grade instruments. While you may further reduce the noise, you may still be at the mercy of the quality of the optics, drive mechanisms, etc. and you may have less noise in the image but the limiting factor is not your image noise but the system limit for drift and distortion.

Some professional instruments use liquid nitrogen cooling while others use thermoelectric cooling, depending on the manufacturer and the intended use. The instruments that use sub-zero cooling also usually have a high quality sensor with a pixel well depth that supports longer exposures, without bleeding effects from adjacent pixels. It all depends on the sensor, camera, and other parts of the system, so your mileage may vary.

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    $\begingroup$ Totally agree. I would like to add and hope that everyone agrees, that even if the cooling is just a few degrees(e..g. 5,10) lower than the ambient temperature it is imporant to have a stable sensor temperature. Then the darks frames should take care of the rest. Cheers everyone! $\endgroup$ – astromath Dec 5 '17 at 23:41
  • $\begingroup$ What are ballpark values for, says, mid range sensor on 600 USD SLR camera, full range value (says 16384), noise at 25 Celsius (says 150), noise at 0 (says 50), noise at -10 (says 30), noise at -20 (says 25) $\endgroup$ – EEd Dec 6 '17 at 17:40

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