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temporary use of mineral oil for cemented binocular doublet objective- caveats?

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#1 pat in los angeles basin

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Posted 17 May 2019 - 07:12 PM

I bought a pair of binoculars and when I found that one of the objectives was partially  de-cemented- Looked cloudy  through about half of the lens, wondered if I could use mineral oil for a temporary interface between the doublet elements while I contemplate what I'm going to purchase to bond the 2 elements (likely Norland #60). I removed the objective from the lens cell and founds that the 2 elements  were completely separated, so all I had to do was clean off the residual  balsam  (early 60's  sunscope wide angle) with a bit of lacquer thinner/ acetone/ goof off to get them ready  for bonding. I'm guessing outside of a thorough degreasing when the time comes to bond that the oil won't be a problem when the final bonding is implemented. Opinions?        Regards, Pat 



#2 Richard O'Neill

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Posted 17 May 2019 - 07:29 PM

Have you tried using them dry?


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#3 Foss

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Posted 17 May 2019 - 07:56 PM

I wonder if oil might migrate to the barrel insides.



#4 pat in los angeles basin

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Posted 17 May 2019 - 08:29 PM

I did try them dry. It seemed to me a bit dimmer with a bit of veiling glare that wasn't present on the other side at low sun angle.

 I don't intend to leave the oil on the lenses. Just for a week or so to see if the bins are worth spending the  dollars on for the lens fix. The fly in the ointment is that the shelf life of the small size (1oz.) is 4-6 months for the uv adhesive.    Regards, Pat



#5 markb

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Posted 17 May 2019 - 10:03 PM

I oil-assembled a impact split 1953 6x30 Steinheil doublet, using the single or so drop on one lens, lowering the other on top, and carefully inserting it into the cell. The cell did the centering and retention.

It was awful before oiling, with the lenses simply held again one another without any interface medium.

I used light motor oil or 3 in 1 oil, perhaps 20 years ago, who can recall. Great results.

The last time I used them 5 or so years ago they still gave indistinguishable images, side to side.

If i have to redo them (great binos, but the value is as family history), I will use a UV cured LOCA as an experiment, or use a proper optical gel or oil.

DavidG has a fantastic thread just this week on decementing balsam pairs, and how to properly recement then. Great like all his posts, search for it.

#6 range88

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Posted 18 May 2019 - 12:06 AM

Photosensitive adhesive is the standard today.

Did you mark the original position before you take out the 2 lens? 


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#7 pat in los angeles basin

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Posted 18 May 2019 - 03:36 AM

I did mark the orientation of the lens elements to themselves and  to the lens cell as well as the cell wrt to the objective bell. Laid out a bit  to check the full moon (or nearly so) image through the 2 sides and found the image no different  from one side to the other- same number of false or ghost moons , same apparent brightness. I'm considering that a success till I get the proper adhesive. A question about balsam - since binocs are more often damaged from a fall more often than a telescope, does balsam typically fail that way? If I use a modern UV cured adhesive  will that likely fail in the same fashion? There might be a reason to favor one bonding agent over the other if that is the case.

 Thanks for the reference to the article in recementing in the classic telescope section  made by DAVIDG. More knowledge is always much appreciated.                             Regards, Pat




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