Resolved Darks, Bias, lights - Background reading zero ADU

Discussion in 'STT Series' started by Nigel Mayes, May 18, 2018.

  1. Nigel Mayes

    Nigel Mayes Cyanogen Customer

    Joined:
    Feb 15, 2016
    Messages:
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    Something strange has happened to our STT-8300M (With selfguiding filter wheel and AO). All of a sudden, images registered only bright stars and the background read zero ADU everywhere. Flats and bias frames were also jet black with nothing on the histogram - reading zero ADU everywhere. I deleted all camera drivers using the DriverChecker. Updated the DriverChecker, updated firmware, reinstalled drivers and still no change. I even loaded CCDOPs and camera drivers on a different machine (Windows 10 vs Windows7) - still no change. Incidentally, I was experiencing the exact same issue on the guiding CCD. I then checked the USB offset. The new values were so different than the previous values and the default values. I reset the EEPROM with the values:

    CCD Offset = 7 in EE for 940 ADU

    The CCD was at -10C at the time. This fixed the issue such that there was the usual noise in the bias and dark frames, but there now seems to be a definite gradient in the bias and dark frames. I can't help feeling that I have compensated for an issue by using the wrong tool. I ran the same procedure for the guide CCD. The darks/bias are not reading zero anymore, but I haven't tested the guide CCD any further.

    I have attached a bias frame from the main CCD where the background is reading zero and a new bias frame after resetting the USB Offset to the above values. This Bias frame shows the gradient - darker at the top and lighter at the bottom. Bias frames taken before this issue started were uniform with no gradient and an average ADU of around 1040. The average seems to be in the low 900's now and gets higher as I move down the frame.

    Up to this point this unit has been a fantastic ,trouble free camera. Thanks in advance for any suggestions.
     

    Attached Files:

    Last edited: May 18, 2018
  2. Doug

    Doug Staff Member

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    There also appears to be pattern noise in the frame. I'm going to guess that an internal power supply has failed. Electronics failures are rare but of course they can occasionally happen.

    What is your camera serial number?
     
  3. Nigel Mayes

    Nigel Mayes Cyanogen Customer

    Joined:
    Feb 15, 2016
    Messages:
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    Hi Doug,

    Thanks so much for your quick response. The serial number for our STT-8300M body is T14030657. I believe this unit was shipped to us from Ottawa on 3/31/2015. As I mentioned, the problem was/is also occurring with the guide CCD. The FW8G-STT serial number is TS15020116.
     
  4. Doug

    Doug Staff Member

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    I have limited test data for that camera, since it was built by the old supplier in Singapore, but the data I have shows that the image offset was set to 153 for 992 ADU. If you had to adjust it to 7 then something is way out of kilter.

    I think you should contact Bill @ SBIG Service & Repair. bill@sbig.com
     
  5. Nigel Mayes

    Nigel Mayes Cyanogen Customer

    Joined:
    Feb 15, 2016
    Messages:
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    Thanks, Doug. I'll do that right away.
     

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