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  1. #1
    carnevali's Avatar
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    Default Learn from my mistake



    If you ever feel the urge to take an eyepiece apart to clean the lenses inside, think twice ... or at least plan more carefully than I did. When they say "7 elements in four groups," they mean it! And the lenses are not necessarily held in place individually, they may just be resting on one another (like they were on my Orion flat-field 16-mm EP), until they pop out when you open the thing and find yourself having to put back together an unexpected puzzle. And then you're just as likely to get specks of dirt, lint and smears on the lenses as you are to clean them. So, if you do, get a clean area, proper tools, and have a plan.
    P.S. I was lucky to be able to put it back together, but I feared the worst for 15 minutes.

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    Antonino Carnevali
    Dobs: Zhumell Z10; SpaceWalk 18"; Celestron First Scope(!)
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    Binoculars: Orion BT70 on VersaGo

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  3. #2
    AustinPSD's Avatar
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    Default

    It is rare, unusual to say the least that an eyepiece would require disassembly for cleaning.

    Almost all modern optics, including eyepieces are compound optics - individual lenses assembled into groups, and groups assembled into the final component.

    Some (eyepieces are good examples) use precision air-gaps in the assembly, as the air/glass interface forms part of the optical path and conversion. If you disassemble the component, and the air-gap is not precise after reassembly, the component will not perform to spec.

    Other components use specialized cements to mate two differing glass types in the lens group assembly - these adhesives can be hygroscopic (attract water, even from humidity in the air), or dissolve in simple solvents like water, isopropyl alcohol or mixtures of these substances.

    A few components have specialized coatings that are only one or two microns in thickness, and in higher-end assemblies, only a few angstroms thick - rubbing them, exposing them to solvents, etc. can damage the coating.

    Many components (especially eyepieces) use air-gapped, asymmetric individual lens elements. If they are reassembled incorrectly (i.e. flipped), the component won't work as specified, and can fail in non-obvious ways.

    It is generally best to clean gently, using pure compressed air, a clean optical camel-hair or synthetic brush, and distilled/deionized water or pure isopropyl alcohol only the outer surface of the eye lens (surface closest to the eye on an eyepiece) or outside of the field lens (inner most lens element), usually within the barrel of an eyepiece - disassembly can result in unexpected, unpleasant, and sometimes expensive repair/replacement.
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  5. #3
    carnevali's Avatar
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    Default

    I'm totally impressed, I didn't know there was so much to know about an eyepiece. I mean, I "knew," but I tend to overlook and not remember.....
    My particular EP had debris inside since I bought it new. I guess it hadn't been assembled in a proper manner. After six months of putting up with all the imperfections I decided to do something about it. I did get rid of the "dirt" and it still seems to be working well .... I hope I was lucky ... but just in case anyone else were to come up with the same idea I thought well to warn. Thanks for explaining why indeed it is NOT advisable.

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    Antonino Carnevali
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  6. #4
    AustinPSD's Avatar
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    Default

    If you ever get an eyepiece, or any other optical component from a reputable manufacturer/OEM/distributor that has a flaw, send it back immediately.

    There is no (good) excuse for sending out a component that isn't perfect, especially one that is contaminated.

    Even on some of today's high-volume lines, the clean-room/contamination profiles should be class ten (no contamination larger than 10 microns). If you get something from a new-in-box purchase that has a flaw like this, something isn't right.

    Most individuals don't have the tools, testing bench capability, or skill set to open up a compound optical component and clean/reassemble/collimate it. Nor should they. Your job is to use and enjoy the component, not troubleshoot or perfect it.
    CGEM 800 HD, NexGuide, Orion XT8 Limited Edition, Oberwerk BT-100, Canon 20D/20Da/T3i/60D/5D Mk III, various eyepieces, adapters, geegaws, widgets, and tiddlybits

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  8. #5
    carnevali's Avatar
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    Default

    Thanks, will do if it ever happens again.
    P.S. I'm very satisfied with the optical quality of the eyepiece, I guess it's a good design, but it was annoying to have it contaminated inside.

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    Antonino Carnevali
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  9. #6
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    Default

    Heavens above Austin! Reading your post on eps was very eye opening to me. I have never cleaned more then the outside of an ep, after reading your post I shall stick to my cleaning way. Thanks for all the information about eps..cements..etc..and well done Antonino for pulling it round!!
    Good job.
    Declan.
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  10. #7
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    Default

    Thanks Antonio and Austin for the "eye opener" on not being an "eyepiece opener". I've never really considered taking one apart, and now I'm pretty sure I never will.
    Mike
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    Starshoot DSI II and all the accessories I can afford for now (unless you guys tell me different)
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  11. #8
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    Default

    Wow... I wouldn't have dared. My bravey only goes so far as picking one up.

  12. #9
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    Default

    Thanks for the warning! Sounds like something I would do...
    Enjoy the Black cause they can't take it back............
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  13. #10
    carnevali's Avatar
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    Default

    P.S. I have used that EP today to look at the sun (through sun filter, of course): works fine. I'm quite relieved. Will never do again (but then I know myself.... don't be surprised if I'll have to renew this thread in the future).

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