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Eyepiece Modifications

Discussion in 'Eyepieces, Barlows, and Filters' started by Mak the Night, Jul 10, 2016.

Eyepiece Modifications

Started by Mak the Night on Jul 10, 2016 at 9:47 AM

8 Replies 2642 Views 0 Likes

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  1. Mak the Night

    Mak the Night Well-Known Member

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    As undercuts can range from being useful to the most infuriating invention ever thought of, I had a bit of a think and decided to swap the draw tubes on some of my EP's.

    [​IMG]

    These bog-standard Celestron (GSO) Plossls now sport chromed brass draw tubes instead of the lighter aluminium ones they originally had. This way, the two 13mm Plossls work well with my binoviewer (which has compression rings) and the 17mm Plossl sometimes comes in useful when used in Barlows.

    [​IMG]

    On the other hand, this 6mm AH Abbe orthoscopic now has an aluminium draw tube featuring an undercut. As it is never used with anything with a compression ring the undercut is no real problem. Occasionally I use it in my Newtonian and the undercut can stop it pulling out of the focuser if it is facing downward. Useful as these Hutech EP's aren't cheap.

    Has anyone else modified an eyepiece from stock?
     
  2. Ray of Light

    Ray of Light Well-Known Member

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    Hey Mak, great to talk again! I have never modified an eyepiece but I fixed an Agena Starguider that arrived defective. As I gain experience I hope to be able to modify my eyepiece kit. Talk soon.
     
  3. Mak the Night

    Mak the Night Well-Known Member

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    Oh yeah, I remember. I don't normally recommend unthreading just any eyepiece drawtube though as the lens elements can drop out on the floor lol. Not good. Most Plossls can have their drawtubes unthreaded though.
     
  4. Don Pensack

    Don Pensack Vendor

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    Try using aluminum or carbon fiber tape to fill the undercut. You may have to do this a few times to get it right.
    You will make the eyepiece 90% easier to insert and remove.
     
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  5. Mak the Night

    Mak the Night Well-Known Member

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    I might just try that Don. I always worry about the tape coming undone though and causing difficulties. My 6mm Hutech ortho' has been reunited with its original draw tube as I've been using it a lot in a TV x2 Barlow and in a Baader helical focuser that both have compression rings.
     
  6. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Well, MTN, you might negate the chance the tape could come un-done while in the focuser by being careful and cutting the tape to be only a fraction of a mm or inch smaller width than the undercut. This way it would hardly make contact with the barrel of the focuser you're sliding it into. It would do precisely what you want it to do - fill in the eyepiece-barrel to be the same as the normal part of the barrel - and not make any more than a glancing touch with the barrel of the focuser. No touch - no abrading the tape and potentialy causing it to migrate off - and get stuck or mushed inside your scopes' focuser.

    You would do yourself a favor by counting as you wind the tape about the undercut so you'd know how many pieces you should cut the next time. Assuming you measure the tape so as to know how many to cut - if you do this one full circle around at a time. At least that's how I'd do it if I felt the need.

    Those undercuts remind me of when bicycle makers started to put these "lips" in the drop-out for removing/replacing the front wheels in what had been called a "quick-release" mechanism - which was designed to make life easier for those who needed to remove the front & back wheels to patch a leak, prevent ride-away thefts, etc. Once in a Blue-Moon someone would fail to reset the quick-release lever and, after hitting a good 'bump' - their front wheel would fall off. And some lawyer you'd see an ad for on Late-Night TV - with a bad toupee sliding around on his head - would be called upon to sue the bike company. So.....

    These new 'lips' were brazed on the drop-outs so the wheel could'nt come off easy. Us mechanics were quick on naming these idiotic things "Lawyer-Lips" and are still annoyed by them!

    Happy taping -

    Dave
     
    Last edited: Jul 31, 2016
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  7. Mak the Night

    Mak the Night Well-Known Member

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    There was a time when undercuts didn't bother me, then I acquired a lot of things with compression rings :eek:. Some undercuts seem to work OK though. TeleVue have basically sussed this with their flared lower lip. I'm guessing TV have patented this as it hasn't been taken up by other manufacturers AFAIK. The only undercuts which seem to be problematical are on the lighter aluminium draw tubes used by GSO predominantly on their Plossls. Although GSO have recently abandoned undercuts, unfortunately there is a lot of stock around still with the undercuts.

    As I'm disabled and my right arm and hand are partially paralysed any tape cutting is going to be extremely difficult for me. However, I am getting more dexterity and range back into my arm and fingers and can do things now I couldn't have dreamed of doing 18 months ago.

    I'm still a little ambivalent about undercuts as a whole, they have actually saved EP's of mine being dumped on the ground, but I've also had to spend time carefully coaxing eyepieces out of my Baader helical focuser. As a rule now I match the eyepieces to the focuser and I've discovered which extract easily through trial and error.

    grabngo.jpg

    The modified Celestron AstroMaster Kit box above contains the eyepieces I regularly use as a grab'n'go box for various scopes. At the moment I'm using them a lot on my 130mm Newtonian. I like to keep them safe in that box as they were all expensive. The 10mm Baader Eudiascopic and 6mm Astro Hutech have no undercuts, the 8 & 11mm TV Plossls work fine and the undercut on the 15mm Antares (Masuyama clone) is no real problem as its barrel is chromed brass and the undercut is relatively shallow. The two eyepieces to the left are mainly used as finders in conjunction with my RACI. The wide angle 15mm Celestron Kellner has a smooth draw tube but the 32mm Celestron (GSO) Plossl has an aluminium draw tube with an undercut. I also sometimes take out a 9mm Celestron X-Cel with the grab'n'go bag. Out of all of them, it's only the 32mm Plossl that will cause any problems.
     
    Last edited: Jul 31, 2016
  8. Mak the Night

    Mak the Night Well-Known Member

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    OK, add one Celestron T-Adaptor and an old GSO draw tube to two basic Celestron Barlows and an old Barlow/T-Adaptor combo and the result is two T-Adaptors (one with an undercut, one without) and two perfectly serviceable decent achromatic light Barlows with removable elements.

    Custom Barlow T Adaptor.jpg

    I really need the clouds to clear ... soon ... as I'm getting too anorak about this lol. :eek:
     
  9. Mak the Night

    Mak the Night Well-Known Member

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    New Revised AstroMaster Box.jpg

    With additional 18mm smooth draw tube Astro Hutech Abbe orthoscopic.
     

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