Another blooming question regarding the 11002

Discussion in 'STX and STXL Series Cameras' started by Anders Hörberg, Aug 7, 2020.

  1. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Hi again guy´s

    Regarding blooming issues with the STXL 11002, as i recall it, i did some change concerning this when i first got the camera back in 2013 with the assistance of some technician at SBIG and it worked fine..

    Cant recall exactly what we did, but as i remember it was adjusting sensitivity in some way for the sensor, now i am a electronic engineer and my business is hardware development, so i dont have a problem adjusting levels if i just have a roadmap on what to look for..

    I have enclosed 2 pics ( dont worry about the poor quality, we have both the moon and clouds here ) and i´m adjusting spacing from flattener, but it´s still very visible

    BR

    / Anders
     

    Attached Files:

  2. Colin Haig

    Colin Haig Staff Member

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    That's mechanical imperfections in your mount in the first image - you can see gaps in some of the stars.
    Have a look at 288,2411 in the 10 minute ic1396 file. I've cropped a bit of it, so you can see 3 stars in the middle, vertically.
    10_crop.jpg
    If you are doing these long exposures, you need to get your mount running well, with guiding.

    One more tip - blooming tends to be symmetrical - the pixels above and below will both be bloomed into. This is asymmetrical, so more likely mechanical or optical.
    This is mechanical - not tracking perfectly.
     
  3. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Hi Colin

    Really? - since this is the same as i had Many years ago as i recall it!...... now if i just focus with the camera and havent the cooler turned on this get 10x More visible at just 40sek test exposure
    Running a 10Micron HPS 1000

    What would you guess it could be? Having a TS Photoline 107mm refractor with A 0.73X flattner 520mm FL
     
  4. Doug

    Doug Staff Member

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    That definitely is blooming. Mild blooming isn't symmetrical; it tends to go more downwards than upwards. Also the background level in the image is awfully high at 36,800 ADU.

    If I had to guess there is an issue with the substrate voltage or CCD clock power supplies. It looks like the camera needs service. Please contact @Bill at SBIG Service and Repair.
     
  5. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Cropped out a star from the 5 min image and stretched it, you mean that this is mechanical? or optical?

    BR
    / Anders
     

    Attached Files:

  6. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Hi Again Guy´s - i sent a private message to bill to get his opinion regarding service, thank you both for the quick response

    BR

    /A
     
  7. Doug

    Doug Staff Member

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    That is blooming.
     
  8. Colin Haig

    Colin Haig Staff Member

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    Why is it gapped Doug?
     
  9. Colin Haig

    Colin Haig Staff Member

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    That looks bloomed at the bottom.
     
  10. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Hi Again guy´s
    I´m on the case after dialogue with Bill

    Can you tell me as reference the VSUB voltage for 60ke as supplied for the chip in my camera
    and what its was set to in this particular build

    Serial: X13050226

    Also is there any reference settings regarding F stops ...tests or anything avaiable? running a F4.8 system so it´s a lot of light coming in of course..
    You guy´s must have made a quadrillion tests when making this cameras so any idea on a "napkin" or whetever would be interesting to see :)

    BR

    / Anders
     
    Last edited: Aug 8, 2020
  11. Doug

    Doug Staff Member

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    Back in 2013 they didn't keep a record of the VSUB setting.

    Could you please post a bias frame in FITS format?
     
  12. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Bias attached

    VSUB Voltage was set to 7V

    Br
    A
     

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  13. Doug

    Doug Staff Member

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    Okay the bias frame looks good.

    We don't have a record of the optimum substrate voltage for your sensor, so I'll give you a simplified version of our adjustment procedure. Since your bias frame looks okay that means your gain/offset settings are good. That makes for a simplified adjustment procedure.

    Increasing (more negative) the substrate voltage results in more well depth but less blooming protection. If you keep increasing the voltage then at some point the image just breaks down - you'll often get what we refer to as "jail bars". That's when you've gone too far.

    Since the gain and offset of your converter has already been set, I would recommend the following:
    1. Start with the substrate voltage at the lower end of the range
    2. Try to illuminate the sensor as evenly as you can. If you have a camera lens that works with your camera, use that with a couple of sheets of white printer paper on top. Or get a foot long piece of PVC pipe and put several sheets of paper on top of it. Use a light source that's fairly constant (i.e. not light coming in the window with passing clouds!)
    3. Adjust the exposure and/or light level until the sensor just saturates (tip: if you have too much light adding more sheets of paper makes it darker). If the substrate voltage is too low, that will happen before it reaches 65,535
    4. Adjust the substrate voltage until the converter just saturates at 65,535. Once you get there don't go any further.
    5. If you get jail bars or other image corruption before you get to 65,535, back off until you get a normal image
    6. Done!
     
  14. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Cool Doug, thanks

    Tried a solution yesterday night, took light frames at 10 sek, 2Min, 5Min, 10Min to a star "arcturus" to see when it became saturated and started having blooming tendecies and adjusted that way..
    The optimal Setting for my camera in that way was 10.35V
    Seem to work very well now..

    Next time i have it off the observatory/Telescope i´ll have a go with your solution to see if we have any differences

    Thank you for all help

    BR

    /A
     
  15. Anders Hörberg

    Anders Hörberg Cyanogen Customer

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    Hi again

    Final question, do you adjust this in room temperature or with the cooler on?

    BR

    /A
     
  16. Doug

    Doug Staff Member

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    Doesn't matter.
     

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