STT-8300M. Any advantage to going colder than -40c?

Discussion in 'Legacy Models - Community Support' started by JoshuaHufford, Nov 6, 2022.

  1. JoshuaHufford

    JoshuaHufford Cyanogen Customer

    Joined:
    Oct 10, 2014
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    Going into winter now with my new to me STT-8300M, with the cooling that this camera is capable of, just curious at what point is there little to gain from going colder?

    Is there a limit in the firmware preventing it from going colder than a particular temp?
     
    JoshuaHufford, Nov 6, 2022
    #1
  2. Doug

    Doug Staff Member

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    The dark current is already negligible at -30C - around 0.2 e-/pix/sec. At -40C that goes down to about 0.05 e-/pix/sec.

    To put this in perspective, a 5 minute exposure at -30C will generate just 60 e- of dark current, resulting in about 7 e- of extra noise. That's already lower than the read noise. Noise adds root-sum-square, so the net result will be about 12 e- per pixel.

    Going to -40C will result in a total noise of 11 e-. Not much of an improvement.

    Because noise adds root-sum-square, the largest noise source dominates. In most situations this will end up being the sky background photon shot noise.

    Another consideration is that the 8300 is not completely immune to residual bulk image, and going colder makes it worse.

    Personally, I've only ever lowered the setpoint below -30C when the ambient temperature was below -30C, and that was only because headroom was needed for temperature regulation! (Yes, once in a while it gets that cold here.)

    As for the lower limit, I'd have to dig into the firmware code to check that... pretty sure it will do at least -50C.
     
    Doug, Nov 7, 2022
    #2
  3. JoshuaHufford

    JoshuaHufford Cyanogen Customer

    Joined:
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    Doug, thanks very much for the detailed response.

    The lower limit isn't a big deal, I was just curious. It never gets that cold here to worry about it. I do remember one user that had a camera which had a cooling limit of -40C, he was pretty far up north and sometimes the ambient was colder than that and he couldn't keep a constant temp.
     
    JoshuaHufford, Nov 7, 2022
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