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Re: USN MkII Sextant Telescope lens coatings and cleaning?
From: Carsten John
Date: 2023 May 23, 09:16 -0700
From: Carsten John
Date: 2023 May 23, 09:16 -0700
Hello Todd,
the lenses in telecopes are usually so-called achromatic doublets, composed of two lenses. Historically, the two lenses were glued together with Canada balsam (this is a tree resin). Today, this is usually done with UV-curing adhesives. The visible damages are probably defective spots in the old gluing of the lenses. I was able to separate the two lenses of an old Plath sextant (built in 1945) in acetone (if that doesn't work, you can also use xylene). I then reassembled the two lenses with UV glue for glass. All in all this was without problems.
Hope this helps
Carsten
