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  1. #1
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    Default eyepiece disassembly?



    I was having some "clouding" issues with my Zhumell Plossl 9mm, so I took it apart. Everything was clean, but I noticed one of the lenses has a hole in its anti-reflect coating.
    On the other lens, holding it under a light and moving it shows a constant anti-reflect coating on both sides, but on the tainted one, there's a spot right in the middle where I can tell the coating isn't there on one side.
    I bought the scope and EPs used, but the guy I bought them from didn't seem the type to take things apart (or abuse them). The problem has always plagued this EP, so it's not a recent development.
    I pulled it apart over a clean white t-shirt, and immediately noticed something was wrong with the tainted lens, so I'm pretty sure it's not something I did. Both of the lenses were clean, but I ran some alcohol over them with Q-tips since I already had them out of the EP.
    Does anyone know what could cause the anti-reflect coating to just vanish like that? I put the tainted lens to the inside of the EP, hoping the "clouding" would be less noticeable that way. The sky has been cloudy since I put it back together, so I haven't been able to see if the viewing is better since my dis/ reassembly.

    Using a Zhumell Z8 that is properly collimated and both mirrors are clean. The "clouding" means that inside a certain region, everything is clear. Outside that (very small) region, everything looks like it's surrounded by mist, even when it's in focus. Everything is crystal clear through my Zhumell Plossl 32mm.
    Last edited by Darth_Firebolt; 02-09-2012 at 07:07 PM.

  2. #2
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    Default

    Those symptoms are identical to my old 25mm and you know what? I dropped it. I mean I dropped the heck out of it! On concrete!

    Maybe the seller did too.

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  4. #3
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    Default

    Some eyepieces are NOT coated (multi-coated) on inside lens surfaces. Its normal for low cost eyepieces. May I encorage you never to take an eyepiece apart. None of us can advise you exactly how to replace the lens elements if you forget how they go back together........... just too many different optical designs.

    Also with expensive eyepieces like Televue's etc etc --- you void the warranty by taking it apart.

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  6. #4
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    Default

    Quote Originally Posted by Joe Lalumia View Post
    Some eyepieces are NOT coated (multi-coated) on inside lens surfaces. Its normal for low cost eyepieces. May I encorage you never to take an eyepiece apart. None of us can advise you exactly how to replace the lens elements if you forget how they go back together........... just too many different optical designs.

    Also with expensive eyepieces like Televue's etc etc --- you void the warranty by taking it apart.

    Clear skies to you.
    This one is clearly coated on both sides of both lenses. The coating has worn off a certain region of one side of one of the lenses. There are 2 lenses with 2 different cuts on each side, giving a maximum of 8 combinations for this EP. If I can't figure that out, I probably don't need to be in engineering courses. I'm also outside the 3 year Zhumell warranty period on telescopes and accessories. Obviously if I purchased a Televue or other high end EP and had this problem, I would send it back.

  7. #5
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    Default

    There are many reasons why a coating would develop a pin hole which grows. That is the problem making them. There are too many ways.

    Cloudy around the edge could be a result of not getting the lenses in right. Your description sounds like a plossl which is two doublets. They must be in the right order to get a flat field.

    Check for chromatic abberation on Sirius, the moon and/or Jupiter. The minimum will indicate the correct order and orientation.

  8. #6
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    Default

    Quote Originally Posted by kencrowder View Post
    There are many reasons why a coating would develop a pin hole which grows. That is the problem making them. There are too many ways.

    Cloudy around the edge could be a result of not getting the lenses in right. Your description sounds like a plossl which is two doublets. They must be in the right order to get a flat field.

    Check for chromatic abberation on Sirius, the moon and/or Jupiter. The minimum will indicate the correct order and orientation.
    Cool. When the weather clears I will check for the aberration. Maybe someone did take it apart before and never got it put back together right...
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    Default

    I wonder if the lens was left out in the sun - I expect heat could play a part in destroying the coatings.
    There's not much else except physical damage and that is rarely even or even regular shaped
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