Dark Frame and Camera Temperature

Discussion in 'STX and STXL Series Cameras' started by Mike Hambrick, Aug 24, 2020.

  1. Mike Hambrick

    Mike Hambrick Cyanogen Customer

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    Orange, Texas
    I would like to get some advice and best practices concerning camera temperature and dark frames.

    Regarding camera temperature, I read somewhere or maybe someone told me that the STXL 16200 temperature will not go below -35 Deg C because there is little or no improvement to be gained by going lower than - 35 Deg. Is this correct ?

    Regarding the camera temperature, I can get to -35 Deg C without supplemental water cooling as long as the ambient temperature is below about 15 Deg C. When the ambient temperature is in the range of 15 to 22 Deg C I can get to -33 Deg C before the camera fan kicks into the high speed mode (which I try to avoid). Above 22 Deg C I can only get down to -32 Deg C. Is there any noticeable performance improvement between -32 and -35 Deg C ?

    Regarding dark frames - I typically keep a "library" of dark frames at various temperatures and exposure lengths to use for calibrating my images. Is there a recommended frequency at which these dark frames should be updated ?
     
  2. Colin Haig

    Colin Haig Staff Member

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    Correct. There is little benefit going beyond that temperature. Secondly, the colder you want the sensor to get and the higher the ambient, the higher the current consumption, so more power is needed to get colder. There are limits, and the -35C is set to prevent electronics from being stressed.
    The camera has an air-cooled Delta T of 50C. So, if it's +20C out, subtract 50C, and the coldest you can expect it to get is -30C.
    If it's +22C and it gets to -33C, that's a Delta T of 55C, so you are doing better than spec with air. Outside air temperature and humidity are a factor, as well as making sure your vents aren't blocked, and the heatsink and fans are clean. I recommend not pushing it beyond our spec.

    The only way to tell is there is improvement is to analyse the images acquired quantitatively e.g. measure a statistically valid sample of dark frames taken at 2 temps eg -35C and -30C.
    Quick and dirty, you could do pixel math and subtract a bunch of the -35C dark from -30C dark, and see if there is a difference of any significance.
    I usually redo my libraries every 6 months.
    Components like electrolytic capacitors in the power section age with time and heat. Other parts age. CCDs get radiation damage from cosmic rays, and local gamma rays (radiation in the soil, concrete, cinder block) etc.
     
  3. Mike Hambrick

    Mike Hambrick Cyanogen Customer

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    Location:
    Orange, Texas
    Thanks for the quick reply Colin
     

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