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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Art Leung
Date: 2023 Oct 1, 08:19 -0700
Bill Morris has an article or two on mirrors:
Mercury amalgam mirrors | The Nautical Sextant (sextantbook.com)
New Sextant Mirrors for Old | The Nautical Sextant (sextantbook.com)
As some of you may know, I have been restoring a Tamaya bubble sextant from 1942. The mirrors had dulled and frosted over the years - not enough that I could not shoot the Sun, but stars were out of the question. The Countinho-type sextants bring tilt and dip bubbles into the telescope view via open areas in the mirroring. I used the method that Bill suggested in the second of the above articles and it came out fairly well.
I started with commercial mirrors cut to the proper X/Y dimensions and rounded the corners using a knife hone in water. For the index mirror, I used a first surface coated mirror. For the horizon/bubble mirror, I used a second surface mirror. The masking was a bit involved but not especially difficult - doing the mask for a traditional split horizon mirror is far simpler.
Commercial mirrors tend to be thinner than historical sextant mirrors. To get them to fit in the depth of the mirror frames, I epoxied some glass microscope slide pieces into the corners and where the mirror adjuster bears.
The original mirrors are safely packed with the sextant.
