"Light ghosting" on brighter stars SBIG 6303e chip - CDK 20

Discussion in 'Legacy Models - Community Support' started by Alan Josefsek, Nov 13, 2018.

  1. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    Can anyone tell me what is causing the light vertical light "band' on some of the brighter stars? Its not regular blooming. On other images it doesn't show up. The "bubble nebula has got several while m71 not so much if at all. Chip m71-20-26f-lucy.JPG Issue???

    Thanks for anyone who can help me figure this out.

    Alan J
     

    Attached Files:

  2. Colin Haig

    Colin Haig Staff Member

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    The very bright stars are swamping the column. An excess of photons causing electron spill ;-) You can probably remove in post-processing.
     
  3. Doug

    Doug Staff Member

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    It is called blooming. The KAF-6303 has a non-antiblooming sensor architecture. NABG has advantages in terms of sensitivity and linearity; unfortunately bright stars can develop these blooms.

    What is happening is that so many electrons are in the pixel that they effectively neutralize the electric fields holding them in place (the CCD clock electrodes), and that allows them to flow along the column.

    Some sensors have anti-blooming features. They bleed off excess electrons to prevent the blooming. It also has the effect of making the sensor nonlinear near saturation and the extra structures can impact the overall sensitivity a bit.

    The options are either to reduce your exposure time and take more images (suffering some additional read noise contribution), or to cosmetically edit the images in post processing. MaxIm DL has a fairly effective bloom removal tool.
     
  4. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    Doug,

    I use MaxDL Pro and the used the Auto or manual Remove Bloom and that's what's left, the "beam of light". It does not recognize it as bloom. It will no get rid of that beam. So how else can you further remove that column of light, because its not obvious to me in MaximDL. I have had the camera for over 5 years with a C-14 and now the CDK 20 since January 2018.
     
  5. Doug

    Doug Staff Member

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    Please upload a FITS version of your image so I can give it a try.
     
  6. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    This a single .fit file. Its mislabeled m71. Should be the bubble.
    Thanks
    Alan
     

    Attached Files:

    • m71.FIT
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  7. Doug

    Doug Staff Member

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    Okay I have had mostly success with the manual removal. Auto did not work. The brightest star has an oddly discontinuous bloom; the tool cleans up the star but leaves a little tail behind. I would nip that off with the clone tool.

    manual.jpg
    Manual bloom tool setup.
    bub.jpg
    Resulting image.

    See http://www.diffractionlimited.com/help/maximdl/Remove_Bloom.htm for detailed instructions on using the manual mode.
     
  8. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    SO why is it doing this? It 1x1 binned .Never saw this with c-14 which was usually 3x3 0r 2x2 binned. Is it the CDK20 is concentrating the light or a chip defect?
     
  9. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    I have tried the manual bloom removal. But it gets that vertical light beam which it wouldn't remove it.
     
  10. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    Would a new chip or camera get rid of this?
     
  11. Doug

    Doug Staff Member

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    This is a characteristic behavior of the KAF-6303 with very bright stars. You will not see that occur with KAF-16803 or KAF-16200, which have overflow drains.
     
  12. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    Doug,
    Will the new STXL6303 sbig camera have the same problem as my older STL 6303e? Any other suggested choices for thCDK20? What are your thoughts about the SBIG AOL with say an 16803 SBIOG. I have been able to get the aol to work with MAXIM and the CDK20 . I had it working with well with my C-14 with CCD Soft. Would appreciate you advices.

    Thanks
     
  13. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    STXL 11002? Would that work or have the same problem? Is my camera considered ok to have a problem if I want to sell it?
     
  14. Doug

    Doug Staff Member

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    Your camera does not have a problem. That phenomenon is simply a characteristic of the KAF-6303. All 6303 cameras will do that.

    Yes the 11002 will not do that, but it is also much less sensitive than the 6303. It will require much more exposure to achieve the same results.

    I would recommend either the 16200 or 16803. Given that you have a longer focal length I would strongly recommend the 16803, because it has a larger pixel size that is better matched to your telescope.
     
  15. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    OK 16803. What about your thoughts on the AOL with it worth it or not?

    Thanks. I was leaning that way.

    Alan
     
  16. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    One to the though the guiding option??
     
  17. Doug

    Doug Staff Member

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    AO-L is a very old model, designed for the STL cameras. We currently sell the AO-X. It's a very nice unit.
     
  18. Alan Josefsek

    Alan Josefsek Cyanogen Customer

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    So the 16801 NABG will have the same problem as the 6303e? Its really the ABG that takes care of it or am I wrong?
     
  19. Doug

    Doug Staff Member

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    The 16801 is usually chosen by researchers who are doing surveys etc. They are looking for the maximum sensitivity and linearity and are no so concerned with cosmetic issues like blooming. It is also a windowless sensor so it has somewhat better quantum efficiency.

    The 6303 is typically used for the same reasons; it is the more economical solution.

    Given that you want large area and anti-blooming, the 16803 is the best sensor for your needs.
     

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