STXL6303 - Horizontal and Vertical Lines

Discussion in 'STX and STXL' started by Cliff Kotnik, Sep 22, 2017.

  1. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    I'm concerned that something is wrong with my camera. I uploaded a master sky flat taken with cooling to -35. See ftp.cyanogen.com/incoming/MasterFlatCliffK.fit. The pattern is pretty obvious at screen stretch "Medium".

    My concern is that this pattern is not being completely removed by calibration and is finding its way into my science images.

    Can you give me your opinion?

    best regards,
    Cliff
     
  2. Doug

    Doug Staff Member

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    Strange! That dip looks like it appears every 36 rows.

    Do you see the pattern on a bias frame?
     
  3. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    I have uploaded a master bias (and a 3 sec dark for good measure) taken on the same night at the same temperature as the flat.

    I do not see the dip in the bias. The major deviation I see in the bias is a fall off in the left most 500 pixels of about 8 ADU. This fall off is gradual and goes top to bottom. It has nothing like the single pixel wide matrix I see in the flat. The master dark, having been bias adjusted has a fairly even salt and pepper shape with the odd hot pixel.

    I'd welcome any suggestions and would be happy to collect additional data to aid diagnosis. I suppose it could be an alien mega-structure in the sky above my observatory that evening, but I suspect it has a more down to earth cause.

    best regards,
    Cliff
     
  4. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    Sorry filenames MasterBiasCliffK.fit and MasterDarkCliffK.fit
     
  5. Doug

    Doug Staff Member

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    What is the serial number of your camera?
     
  6. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    Doug,
    The shim placement document that came with the camera is dated March 4, 2016 and shows serial number X16010007. My camera is in my observatory and it will be a day or two before I go there. Let me know if I need to check this against the physical camera.

    best regards,
    Cliff
     
  7. Doug

    Doug Staff Member

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    Unfortunately I don't think we have an image saved from your camera. (We do that routinely now.)

    It may have to go in for service.
     
  8. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    Ok. Please tell me how to proceed with service.
    Cliff
     
  9. Doug

    Doug Staff Member

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  10. Doug

    Doug Staff Member

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    So we've done a lot of investigation on this. We tried adjusting your camera's clock voltages and timing, changing bias levels, all sorts of things and nothing changed.

    We just built a batch of 6303 cameras, so we have a bunch of test subjects. Also we have a vintage 2000 camera (not SBIG) with a 6303 sensor. We also located an old (slightly damaged) sensor we had in engineering inventory. ALL of them exhibit faint lines like yours.

    There is one difference between the new sensors and old sensors. On old sensors the pattern is a little bit random looking, but it doesn't move around from image to image. On the new sensors the lines are always exactly every 36 rows, but they're not in the same location on different sensors.

    The clincher was when we swapped sensors between two of the new cameras. The position of the lines moved with the sensors.

    I have taken many 10s of thousands of images over the years with the old camera (it was used for Desktop Universe, among other things), and have lots flat-field frames. Proper calibration renders the lines undetectable.

    I have an inquiry into ON Semi about the lines, but I suspect that won't get us anywhere. These lines appear to be characteristic of KAF-6303 sensors.
     
    Bill likes this.
  11. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    Wow! I didn’t realize this would be so involved. I was digging into this because I saw the horizontal lines in some calibrated images. I am traveling until Monday and don’t have access to images so I cannot dig up an example until then. I suppose another way to approach it would be to calibrate some of the flats that go into a master flat?

    Anyway, I’ll wait until I hear what your inquiry turns up.

    Thanks for keeping me informed.
    Cliff
     
  12. Doug

    Doug Staff Member

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    At this point we've reached the end of the investigation, barring any substantive response from ON Semi. I honestly don't hold out a lot of hope for that. The fact that a 17 year old sensor shows the same behavior suggests this isn't going to change. Also that old sensor was in a camera of completely different design, so it's definitely not something we are doing.
     
  13. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    Yes, I took that as what you were saying. So give me until Tuesday to look through my images. Hopefully you will have a response by then, if only unsubstantial. We can figure what to do then.

    Best regards, Cliff
     
  14. Cliff Kotnik

    Cliff Kotnik Cyanogen Customer

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    Doug,
    I think we should take further discussion out of the forum. I sent an email to Tim and Bill and asked them to forward it to you.
    Cliff
     

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