SBIG ST2000XM - need to clean CCD sensor and CCD glass ontop

Discussion in 'STF Series CCD Cameras' started by Konstantinos, May 23, 2016.

  1. Konstantinos

    Konstantinos Standard User

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    Hi
    I have a second hand SBIG ST2000XM with CFW9 camera for some years and until now it worked perfectly.
    Last time I noticed some flexure on my imaging setup and I decided to open the camera and tighten up a litlle bit more the filter wheel 4 screws to the camera body without opening the CCD chamber. After that my problem begins.

    I see dust motes on my flats more than expected. I open the camera again and open the CCD chip chamber. With a blower I blow some air on the CCD chip and seal back the camera. The camera is working perfectly again but after some days I see again more and more dust motes on my flats.

    I open again the camera and try to clean the CCD chip and the CCD glass window ontop of the chip. I used isopropyl alcohol for this job. A complete disaster after that. Check my flats.

    https://www.dropbox.com/s/l5pqprkvf4myv75/BAD-FLAT.jpg?dl=0

    Can this mess be fixed and how? Also I am worried even if it can be fixed, after sealing the camera again the problem sooner or later will appear again. Because the trapped air in the CCD chamber is not pure and dust particles are floating inside. Also the 4 screws of the filter wheel are overtighten and throw metallic particles on the CCD chamber.

    Thank you
     
  2. Tim Puckett

    Tim Puckett Guest

    I would send it to repair. Just changing the desiccant should not create this much dust.

    Authorized Repair Center
    Bill Lynch - SBIG Service & Repair Center(please note new address)
    130 Castilian Drive, Suite 102
    Santa Barbara, CA 93117
    Bill Lynch - bill@sbig.com
    Phone: (805) 308-6979
    Note: Please contact our authorized service & repair center for an RMA number prior to returning your equipment.


    If you have to tackle it own your own describe your work environment where you are doing this.
     
  3. Colin Haig

    Colin Haig Staff Member

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    Yes, it can be fixed. Definitely a mess. You might want to send the camera in to SBIG for service - contact Bill.
    If you want to try again, here's an approach that might work for you.
    In the cameras I've cleaned, you have to start with a clean workspace, with minimal dust and no moving air if possible.
    Start by cleaning yourself. Cotton (non-static) clothing is good. Washing your hands, and removing any finger grease with an orange cleaner and then isopropyl alcohol.
    Clean the exterior of the camera, getting all dust off with Kimwipes (dust-free tissues) used for camera lenses.
    http://www.mgchemicals.com/products...imtech-science-precision-wipes-tissue-wipers/

    The trick is to prevent transfer dirt from you to the camera, and from the outside of the camera to the inside.
    This will take several iterations. Use the wipes only once and toss them immediately.
    Stay away from the optical surfaces, till the mechanicals are spotless.

    After you get the exterior done, you'd want to remove the nose piece, filter wheel, etc.
    Clean again carefully, as there may be small metal particles from the screw threads.
    I often use cotton-tipped stabs (like Q-tips) to get ride of metal from nooks and crannies.
    http://www.mgchemicals.com/products/cleaners/swabs/tapered-cotton-swab-8112/

    For cleaning fluid, you need top grade 99.9% Isopropyl Alcohol:
    http://www.mgchemicals.com/products/cleaners/electronic-cleaners/isopropyl-alcohol-824/
    Be wary of stuff from the local drug store - often it is only about 80%, and not that good.

    Instead of a blower, you need something like this, which is optically and electrically safe:
    http://www.mgchemicals.com/products/dusters-cold-sprays/dusters/super-duster-134-402a/
    Again, be careful what you buy. Some of the stuff out there will leave moisture or stains.
    And never tilt the can! Keep it vertical. It will get very cold when used, so small bursts are ok.

    Once all the mechanicals are done, then it is time to move to the chamber window and so on.
    One way to keep the dust down during this process is to use a new, large zip-lock freezer bag.
    They tend to be very clean, and you can put the camera inside it, and get hands/tools in there.

    Your flat shows me the outside optical window has streaks from the cleaning - probably contaminants were spread around the window, and so the 99.9% alcohol would help get rid of. Tiny amounts on the Qtip, floated across the window (not scrubbed), and toss each q-tip after 1 wipe. If you are still having problems with streaks on the outside, maybe a single drop of dish soap (Dawn), and an equal mix of isopropyl and 100% distilled water, might help. You should be able to do it with isopropyl alone.
    You might use a Kimwipe at the edges of the window to absorb extra stuff.

    At this point, you might want to shoot through the camera and see how improved.

    Your image showed that there are a lot of tiny spots on the chip. Best bet might be to remove the dessicant plug, and then clean the screw threads only with an alcohol damped Q-tip. Then insert the stick nozzle from the Super Duster into the chamber, and gently trigger it. A vacuum source outside the chamber will help remove the related particles. Try to keep from aiming the blast onto the chip.

    At this point, you might want to shoot through the camera and see how improved.
    Seal it up and re-assemble.

    I've heard some people have used CO2 cartridges with special swabs for camera sensors, but have no experience personally.
    The main thing is don't rub the dirt/dust against the optics, and toss out the cleaning wipes/qtips after each stroke.

    Good luck, but again, you might want to contact Bill Lynch.
    Colin
     
  4. Konstantinos

    Konstantinos Standard User

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    Hi

    Thank you all for your replies.

    I continued my experiments to clean the camera.
    This time I used these glasses wipes from Lidl (cost 1,11 Euro)
    https://www.pentaxuser.com/images/comment_pictures/20982/20982_1423777878.jpg
    and a mobile phone monitor tissue.

    Use W5 glasses wipes first then immediately the mobile phone monitor tissue to absorb the moisture.
    I did this on the CCD sensor surface and on the glass window which covers the CCD sensor chamber.

    Then I took flat frames with the camera connected to the FLAT BOX only and bingo!!! The flats look very good now the dirt has almost gone.
    But as you can see there a few motes just a few. These dust motes are not on the CCD sensor surface but on the the glass window which covers the CCD sensor chamber. It's easy to see this because they are big and not focused..

    See the camera flats here: https://www.dropbox.com/s/sq5gdb48i54elds/FLATS_camera.zip?dl=0

    After that I connected the camera to my two telescopes one each time and took a flat frame.
    Both telescopes show the same dust motes and in same position.

    Vixen ED81s flat: https://www.dropbox.com/s/07h79ic9zmetzhj/FLAT-LUM-telescope-VixenEd81s.jpg?dl=0
    Vixen VC200L flat: https://www.dropbox.com/s/dg9my8slmc7mabm/FLAT-LUM-telescope-VC200L.jpg?dl=0

    My experiment proves that there are some dust motes on the the glass window which covers the CCD sensor chamber. I will need to repeat the cleaning only to this window.

    Hopefully my problem will be completely solved after that :)
     
  5. Colin Haig

    Colin Haig Staff Member

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    I had a look, and its much much better. Well done. Your filters seem clean and the flats are pretty good. The flat for the VC200 looks better than the ED - its more what I would have expected.
     
  6. Konstantinos

    Konstantinos Standard User

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    Hi

    My assumption was wrong. The dust motes were not in the chamber glass window but on the surface of the CCD sensor.

    I tried to clean again the CCD sensor and now almost all the dust motes are gone as you can see in the attached flat frame.

    The flat frame was captured with the camera attached to my telescope Vixen ED81s.

    Here's the latest flat frame: https://www.dropbox.com/s/e8cu002pybqkvmr/new-flat.jpg?dl=0

    You can compare it with the old flat frame with this setup: https://www.dropbox.com/s/07h79ic9zmetzhj/FLAT-LUM-telescope-VixenEd81s.jpg?dl=0

    But unfortunately the sensor is scratched now in the top left corner you can see the black line.

    I would like to ask you if this is a big problem or this scratch can be removed after calibration of my light frames with the master FLAT frame.

    Thank you
     
  7. Konstantinos

    Konstantinos Standard User

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    I will check the ADU value in the defect. I guess if it reads 0 then it must be a scratch on the CCD sensor. defect.jpg
     
  8. Bill

    Bill SBIG Service and Repairs Staff Member

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    It's not a scratch, promise.
     
  9. Colin Haig

    Colin Haig Staff Member

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    Agree with Bill.
     
  10. Konstantinos

    Konstantinos Standard User

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    Hi

    I have measured the ADU value inside the area of the streak and as you can see it's about 31,000 ADU

    This proves is not a scratch on the CCD sensor. Maybe the streak is a kind of salted substance on the surface of the CCD sensor.

    This could explain why it always remain still despite the methods I have used to clean it (cotton swabs, microfiber tissue, blower).

    If this is the case what is the most effective method to remove salted substances from the CCD sensor?

    And here's the original flat FIT as requested: https://www.dropbox.com/s/tcezzncsz9ihlzs/streak.fit?dl=0

    Thank you streak.JPG
     
  11. Colin Haig

    Colin Haig Staff Member

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    Did you use a solvent?
     
  12. Doug

    Doug Staff Member

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    Just FYI, On Semi (formerly Kodak) recommends only 100% pure ethanol as a cleaning solvent. Yes that is very hard to come by. The don't recommend anything else because of the risk of damaging the optical coatings.
     
  13. Konstantinos

    Konstantinos Standard User

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    Last edited: May 25, 2016
  14. Colin Haig

    Colin Haig Staff Member

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    I think you managed to smear a dot of contaminant across the surface of the chip. You could use that, but purity is important.
     
  15. Doug

    Doug Staff Member

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    All I can say is that On Semiconductor does not recommend isopropyl. You probably will get away with it, but it's officially not recommended.

    Most certainly do not use methanol!
     
  16. Colin Haig

    Colin Haig Staff Member

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    Doug, that's good to know. Ethanol 100% is very hard for the average person to obtain.
     
  17. Doug

    Doug Staff Member

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    Impossible in Ontario. We had to get a special permission letter from the LCBO, and there's only one authorized supplier.

    In the USA it is state-by-state. In some places it's no big deal. I'm told University of Hawaii actually had to get a liquor license for Mauna Kea!
     
  18. Konstantinos

    Konstantinos Standard User

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    Hi
    In my country Greece, the only I can find is ethanol 95% pure. Can I use this solvent on the CCD sensor?
     
  19. Doug

    Doug Staff Member

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    Assuming the other 5% is simply water, should be no problem.
     
  20. Konstantinos

    Konstantinos Standard User

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    Hi

    The camera sensor was cleaned for a last time with attached cleaning solution.

    This is the latest flat frame with the camera attached to my refractor telescope: (see image flat.jpg)

    Unfortunately the streak cannot be gone it is indeed a little scratch on the ccd sensor protective layer.

    But the good news now.

    This is a 20 min test light frame exposure: (see image light-20min.jpg)

    This is the light frame calibrated only with the flat frame: (see image light-20min---cal.jpg)

    Success the streak is gone also the dust motes and vignetting. Flat frame made its magic :)

    Thank you all very much for your support.

    Regards, Konstantinos
     

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