16803 dark frame blooming?

Discussion in 'STX and STXL Series Cameras' started by blackdragon72, Aug 24, 2020.

  1. blackdragon72

    blackdragon72 Standard User

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    Just looked at my 16803 master dark frame and noticed some thing weird.
    Does it looks like blooming in dark? The hot pixels are far from saturation.

    It is -20C 600s master dark frame.
     

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  2. Doug

    Doug Staff Member

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    It's not blooming, it is trailing charge.

    What is your camera's serial number?
     
  3. blackdragon72

    blackdragon72 Standard User

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    What is trailing charge? Does it require hardware fix, firmware update or can be calibrated out?

    Serial number is STX16803 16060001.
     
  4. Doug

    Doug Staff Member

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    It means that some of the charge is trailing behind when you clock out the sensor.

    The test data from when it was built in 2016 all looks good. It may require a hardware fix. Please contact Bill at SBIG Service & Repair. bill at sbig dot com.
     
  5. blackdragon72

    blackdragon72 Standard User

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    Does it mean the same artifact will be seen in light frame for brighter stars? I have not done long exposure so I have not seen it.
    Is it a complicated hardware fix?
     
  6. blackdragon72

    blackdragon72 Standard User

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    And is it easy to be seen in light frame?
     
  7. Doug

    Doug Staff Member

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    Yes it is possible that you would see it on bright, tightly focused stars.

    Hard to say what the fix is without knowing what is wrong; there are several possible causes. It may need to be repaired, though it is possible that a clock voltage needs to be adjusted.
     
  8. blackdragon72

    blackdragon72 Standard User

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    So it is more like blooming that only show up in certain condition, not for every star.
     
  9. Doug

    Doug Staff Member

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    I guess you'll have to decide for yourself whether it is affecting your imaging or not.

    I couldn't do any quantitative measurements on it because you uploaded a JPEG. I'd need a FITS file for that.
     
  10. blackdragon72

    blackdragon72 Standard User

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  11. blackdragon72

    blackdragon72 Standard User

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    And will it be degraded over time so I will have to fix it sooner or later?
     
    Last edited: Aug 24, 2020
  12. Doug

    Doug Staff Member

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    Unfortunately those images were all processed in PixInsight, so I can't use them. I need RAW frames directly from the camera.

    There's no way to know. If it's a hardware failure it could become progressively worse... or not. It depends on what failed.
     
  13. Doug

    Doug Staff Member

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    The unprocessed dark frame you sent me comes in at 1.2% horizontal trailing charge. It's actually within our specs. It just looks bad when you stack a lot of frames.

    Can you upload an unprocessed light frame?
     
  14. blackdragon72

    blackdragon72 Standard User

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    Doug,

    Thanks!

    What is the spec value? Is 1.2% more typical? Does it help if I send the CCD to Bill to improve it?
    I have not done long exposure yet. How long should be the light frame exposure?
     
  15. blackdragon72

    blackdragon72 Standard User

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    And do you have measured value when it was manufactured? Did it degrade over time? I am asking because if it falls out spec later and I send CCD for repair, then it may be out of warranty.
     
  16. Doug

    Doug Staff Member

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    The measured value in production was 1.18.

    Your camera was built in 2016.
     
  17. blackdragon72

    blackdragon72 Standard User

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    The camera was purchased new about 2 years ago.
    I used another 16803 and it did not look this, I could hardly see any trailing. So is 1.2% typical or much worse than typical? Shall I send the camera for checkup and tuning?
     
  18. Doug

    Doug Staff Member

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    Okay, I found your camera's history. We shipped it to Oceanside in June 2016. I know they don't worry about selling old stock first, but that's a long time sitting on the shelf!

    1.2% is typical, though it's usually shorter and brighter rather than longer and fainter. Each sensor has a unique character!

    It's very faint. If you can't see this in your final calibrated images, I would not worry about it.

    If you want to send your camera in, we can try to tweak the horizontal clock voltages slightly to reduce the effect. It's up to you.
     
  19. blackdragon72

    blackdragon72 Standard User

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    Thanks! That explains what I saw in another 16803.

    What should be the light frame exposure time I should use to check for this affect? And which filter?
     
  20. Doug

    Doug Staff Member

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    Filter shouldn't matter. Just use the camera normally, and examine your calibrated and stacked frames critically. You shouldn't be able to see anything. Look at the right-hand side of the brighter stars.
     

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