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Posted By: Walt Mathers on: 09/04/2005 12:06:27 EDT|
Subject: Telescope & Marine Glass Lense, Observations Concerning the Care of
Three principle reasons why 1860's period optics lose servicability ('tis a good Army Qrmstr term) are:
1. Interior lenses become dirty over time in the field and should be examined by un-screwing them from their tubes and observing the condition of each by holding them up to a light source. Camera lens paper works well for cleaning. Do not suffer using newspaper as t'was prescribed for field expedience in the early 1860's.
2. In the course of using a glass, any of the individual lens, which are mounted in brass and either screw out of the tube's female threaded-end, or, as in some cases, are inserted as friction sub-tubes into the larger tubes or 'pulls', MAY become dislodged and thus will adversely affect the focus of the entire view. A lens might be perfectly perpendicular to the direction of the tubing thus giving the impression that all is clear and visable clear through when pearing down into the object (large) end of the glass.
3. Over the course of a century or two (or sooner if extreme temperatures have been allowed to have their way upon the instrument) some of the individual lens sets, made up of both concaved and convexed, are found to have experienced a chemical breakdown of the glue which holds them together. This crystalization (usually appearing to be faintly of green tint) will 'fog' the lense. When this occurs the two pieces of glass which make up such optics must be heated to separate the glass, cleaned of old residue and then re-glued with heat to melt the glue evenly throughout the surface of the lens.
I hope any of these three suggestions help but least of my hope of the three is the third, as you will need to look outside for help with such a project. We must remember that technology has changed greatly since these optics were developed. The art of flame-gluing the lens glass is dying.
Then again, as Dave Gaddy has mentioned, having need for such things on a regular basis, Malcolm Addoms may well have a 'bead' on knowing a yet-practising artisan. There is a retired eye doctor/signal re-enactor named Don Chaputa of Allentown, Penna., who once had optics restored in a pair of my marine glass that had crystalized.
Much success with your newly acquired telescope but I recommend that you take your glass apart first to see which of the three issues you may have to address. It may save you a lot of money.
Signal Corps Association (1860-1865)