Ice on the outside of window?

Discussion in 'STX and STXL Series Cameras' started by Rick McAlister, Mar 2, 2017.

  1. Rick McAlister

    Rick McAlister Cyanogen Customer

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    Does ice ever accumulate on the outside of the imager window as opposed to the inside? My STXL 11002 has had icing visible since I bought it over a year ago. I've regenerated the desiccant multiple times (every three months or so) without a notable difference. The frost appears only on the edges and corner of the image and dissipates within 20 minutes, so I don't let it worry me. I might add that it is commonly warm and somewhat humid here in Hawaii when I'm shooting, and I run the temperature at about -20C. If not exterior frosting, is this indicative of a leaky chamber? Thoughts?

    - Rick
     
  2. Doug

    Doug Staff Member

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    A leaky chamber would frost inside, on the chip, not outside or on the front window.

    It's very unlikely that the front window could frost up. Dewing up is possible, but there is a window heater that should prevent that.

    I'd suggest next time you see this that you take the camera off the scope, open the shutter, and shine a light inside. You probably would be able to see it.

    I would also suggest recharging the desiccant.
     
  3. Rick McAlister

    Rick McAlister Cyanogen Customer

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    Hmmm. Well, it's definitely frost -- I can see the crystals in the image, so that seems to pretty much rule out dew. I'll pull the camera first opportunity and do the visual as you suggest. Then I'll recharge the desiccant yet again, wait a couple of days for the chamber to totally dry out (if it's going to) and repeat the experiment. I'm assuming that if I still see frost on the chip on the second go then I've got either a leaky chamber or ineffective desiccant. But, we'll see. Thanks the guidance.

    - Rick
     
  4. Doug

    Doug Staff Member

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    What is your camera's serial number?
     
  5. Rick McAlister

    Rick McAlister Cyanogen Customer

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    X15060001

    - Rick
     
  6. Doug

    Doug Staff Member

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    Please do repeat the desiccant recharge. If that doesn't work then it's still under warranty so Bill can check it out for you.
     
  7. Rick McAlister

    Rick McAlister Cyanogen Customer

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    Just a follow up on this thread.

    Three weeks ago, I performed a visual as suggested and verified moisture inside the CCD window. I then recharged the desiccant (4 hrs @ 350 degrees) and let the camera "soak" for 24 hrs. I then recharged the desiccant again (4 hrs @ 350 degrees) and let the camera soak for another 48 hrs. Since that time I have seen no evidence of moisture (around 7-10 nights of shooting). It's entirely possible that despite several more widely spaced rounds of recharging over the past year or so, I never did get the chamber entirely dry. On the other hand, I may just have a very slow leak. The manual implies that I shouldn't need to recharge but every year or so. I'll keep an eye on it an let you know how long I go.

    - Rick
     
  8. Colin Haig

    Colin Haig Staff Member

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    If your dessicant plug is like those I recall, it could be a bad o-ring - you did take it off during baking, right?
     
  9. Rick McAlister

    Rick McAlister Cyanogen Customer

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    You could be right on the o-ring. Each time, I did remove it for baking, examined it carefully for cuts, flatness and dirt, as well as gave the ring a very light coat of vacuum grease before reinstalling, but you never know. For instance, my eyes would never be able to tell me if it were marginally under-spec for it's seating groove (or vise versa). The other possibility of course is the front window seal, but I really don't want to go there. For now, I'm going to stick to my theory that I just never got the chamber fully dried out until now (at least if moisture doesn't show up again prematurely). Makes me sleep better. Thanks for your thoughts, Colin.

    - Rick
     
  10. Colin Haig

    Colin Haig Staff Member

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    Good luck with it Rick. I'm always a bit nervous around vacuum grease, as I had some outgas, and that was a pain.
     
  11. Rick McAlister

    Rick McAlister Cyanogen Customer

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    I'm not quite sure how to take that... :)
     
  12. Colin Haig

    Colin Haig Staff Member

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    LOL - yeah, ingesting it is not good, causes rude noises ;-)
    I meant that it outgassed leaving a thin slimy deposit on the inside of the equipment piece it was applied to.
     
  13. Rick McAlister

    Rick McAlister Cyanogen Customer

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    Well, bad news. After less than a month, the frosting is back. Attached is a flat frame taken about 5 minutes after the CCD reached a temperature of -20C (down from about 16C). Points towards a leak.
    What are my next steps?

    - Rick
     

    Attached Files:

  14. Tim

    Tim Staff Member

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    There must be a leak somewhere. Probably best to just send it to Bill and have it resolved once and for all.
     
  15. Rick McAlister

    Rick McAlister Cyanogen Customer

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    Thanks, Tim. I'm working on getting the camera to Bill now.

    - Rick
     
  16. marc4darkskies

    marc4darkskies Standard User

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    Just thought I'd chime in on this thread since chronic frequent icing of my STXL 11002 has been a problem for me also (usually about a month or two after recharging the desiccant).

    My camera has been to the local distributor (in Australia) who has checked the camera over including the chamber seals and found no issue. However, I always thought the desiccant plug o-ring was slightly under spec for the seating groove because when replacing the plug after a recharge there never seemed to me much, if any, engagement evident from the o-ring before the screws were fully home. I have now replaced the o-ring with one of the same diameter but very slightly thicker than the SBIG supplied one and the 0-ring now feels like it's being well engaged before the screws are fully home.

    Also, after the last time I recharged the desiccant (and replaced the o-ring), the rear plate/cap on the desiccant plug came off (!!) as I was placing it in the camera (circled in the image below). Thankfully, I caught it quickly so only a few grains of desiccant spilled into the camera. I now suspect that the main culprit for my chronic icing was that the seal around that end plate was imperfect from the get-go, exposing the desiccant to the atmosphere enough to become discharged in about a month or two. SBIG has sent me a replacement plug. In the mean time I placed the faulty plug back in the camera after reattaching the end plate and sealing the joint with electrical tape. So far a month has gone by without any sign of icing so I'll be interested to see if the new o-ring plus my high-tech electrical tape seal around the plug's end plate makes a difference. I'll put the new plug in when the old one is again discharged.

    My advice is check the end plate on your plug when you recharge it to make sure it's not loose!

    Cheers, Marcus

    [​IMG]
     
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  17. Doug

    Doug Staff Member

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    FYI we have changed the adhesive used for the cover on the desiccant plug.
     
  18. Rick McAlister

    Rick McAlister Cyanogen Customer

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    Marcus, Doug,

    Thank you very much for your comments. Marcus's experience sounds like a very plausible explanation for mine. I had noticed that the desiccant plug seemed to bottom out without resistance when installing, but wasn't smart enough to draw a connection. I'll see about getting the O-ring spec from Bill and trying some experiments when I can. It may be a couple of months before I can do all this as my camera is 3500 miles away this time of year. But, I'll report out as soon as I can get to it. I'll keep an eye on the cover as well.

    Much obliged,

    - Rick
     

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