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Thread: Recementing lens element

  1. #1
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    Recementing lens element

    I have no idea where to put this, really, but here goes:

    I have had the idea (on and off) to recement the rear element of an old brass Rodenstock (it's an Aplanat). It has balsam separation on the edge, and I am thinking of it as a project lens, as the element is very easy to take out. I guess sending it off to a specialist like John at Focal Point would be nice, but the value of the lens (apart from its sentimental value to me) is low. Doing it myself, I understand the risk of getting dust in there, and it not being centered, etc, so... maybe should I just leave as it is?

    Where can I get some Vblocks (I guess they are called that?) or prisms to do the centering?

  2. #2

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    Apr 2009
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    Re: Recementing lens element

    See "Protocol For recementing lens elements, by John Schneider, here, on "Lenses and Lens Elements"...

  3. #3

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    Pac. NW, USA
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    Re: Recementing lens element

    This might be one source for some Canada Balsam...when it comes time to re-cement.
    I don't have any personal experience/connection with the company, just passing on some info for your project.

    Marc

    http://www.surplusshed.com/pages/item/b1077.html

    Also, a related APUG Thread:

    http://www.apug.org/forums/forum85/9...adabalsam.html

  4. #4
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    Re: Recementing lens element

    Thanks for the information, gentlemen.

  5. #5

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    Re: Recementing lens element

    Dust and air bubbles are really not a problem. It is possible to check for success before the final "baking". And the two parts can be splilt and cleaned without difficulty and a new attempt made. Use of tooth floss, rather than V blocks is reccommended.
    My experience of Aplanats/RRs is that they are quite easy - as long as the lens can be removed from the cell.
    If it is just the single lens, I might be able to help you with Canada Balsam - considering you are local!

  6. #6

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    Re: Recementing lens element

    Quote Originally Posted by imagedowser View Post
    See "Protocol For recementing lens elements, by John Schneider, here, on "Lenses and Lens Elements"...
    Where is "HERE"?
    Not on this forum, i guess, since i have done a search and found nothing.
    Maybe it's a book.
    BTW, i found a series of four nice books, of which you can find many different editions (second-hand, i i got them from Amazon), which are about making yourself astronomic instruments.
    I have the first three books of the series, and there are many paragraphs which are of great interest for the vintage lens enthusiast. In particular there are many infos about lens grinding and cementing.
    I confess that i have read only a small part, and that weeding out what's unimportant can be quite tiresome, as most of the stuff is about telescopes and other astronomical matters.
    Nevertheless, there are lots of infos that can't be found on other books/Web resources.
    The title of the books is:
    Amateur Telescope Making by Albert Ingall
    There are at least five editions, over a good span of time, and 3 or 4 volumes (i must go by memory now).

    have fun

    CJ

  7. #7

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    Re: Recementing lens element

    Cyber, Look at the bottom of this page, under "Similar threads"

  8. #8

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    Mar 2010
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    Bologna, Italy
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    Re: Recementing lens element

    Quote Originally Posted by imagedowser View Post
    Cyber, Look at the bottom of this page, under "Similar threads"
    My fault, my fault
    I made a search, though, and didn't find that thread...

    In the meantime i've made another search: browsing through my Amazon purchases, i found that "Amateur Telescope Making" was released in countless editions, i found a fourth edition that was printed during the fourties. There was a later revision, updated and revised, that was published on 1996. I hope that informations about lens work are still there, as most recent books on the same matter concentrate only on mirror making.
    The complete set is made of THREE volumes, not four. I was wrong. Some recent ones are titled "Amateur Telescope Making, Advanced". I think it's the second volume.

    have fun

    CJ

  9. #9

    Join Date
    Feb 2006
    Posts
    3,112

    Re: Recementing lens element

    Quote Originally Posted by Jimi View Post
    I have no idea where to put this, really, but here goes:

    I have had the idea (on and off) to recement the rear element of an old brass Rodenstock (it's an Aplanat). It has balsam separation on the edge, and I am thinking of it as a project lens, as the element is very easy to take out. I guess sending it off to a specialist like John at Focal Point would be nice, but the value of the lens (apart from its sentimental value to me) is low. Doing it myself, I understand the risk of getting dust in there, and it not being centered, etc, so... maybe should I just leave as it is?

    Where can I get some Vblocks (I guess they are called that?) or prisms to do the centering?
    You can find V-blocks at McMaster-Carr.com.
    One man's Mede is another man's Persian.

  10. #10

    Join Date
    Oct 2007
    Posts
    732

    Re: Recementing lens element

    My urge to DIY certain things is selective. What you are considering is a NO for me. I just received back a lens from John at Focal Point. Job done excellent, and turnaround quite fast. However, the element(s) that were separating were three pieces of glass. Price was slightly more than the value of the lens in a quick sale market, but I decided to have John repair it.

    Sometimes it's not about the money. I don't say that because I have a lot of "scratch". I am retired on a fixed income, and my expenditures are well thought out.

    However, sometimes I make a decision based on other factors... one of which is that I decide I just want to see the result of a project. If it works out..great. If it turns out that it doesn't work as I'd hoped, I am prepared for that risk.

    When I think of some of the things I have spent money for over the years, the decision I made to fix the lens I already owned was spit in a bucket. I now have a known quantity, as opposed to going into the market and buying another unknown lens. I feel good about that.

    Bottom line, what I am saying is, it sounds like this is a bit of an experiment for you on this particular lens, and perhaps the challenge of DIY. However, I endorse Focal Point. The money.... would rather have a qualified repair and get the results I am looking for. Certain pride in that. Your question might be, to yourself, "what do I reasonably expect as results from this lens, with a quality repair at what price?" Second question might be, "Am I OK to lose what image quality I have now if I TFU the recementing?" and last, if my time is money? (an often overlooked question for most for hobby type functions), how much am I actually spending to research the repair, separate and clean the lens elements, gather the tools and equipment, and forge ahead with the repair.

    Personally, I can still bill myself out for $50 per hour (nominal... not too low, but below market) doing computer tech'ing as I have for the last 20 years. So, a $300 repair, I can cover in 6 hours of computer work.

    So, I'd farm that job out in a heartbeat. Recementing my own lens would be a minimal source of pride, AND it's not likely I am going to go into the business and compete with John at Focal Point.

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