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    Bris Sextant
    From: John Rae
    Date: 2005 Oct 30, 16:10 -0800
    Thanks Alex for your information.
    Yes, I made the test sextant from three pieces of plain glass, and used my mountain sunglasses (<7% transmission), but even so, I was careful to block the true sun with my hat brim and finger.  This may be OK for a test, but obviously not for a working sextant.
    I intend to use a colored glass for one of the elements of the next sextant I make.  A local camera store that has an extensive stock of used cameras, lenses and accessories sells used filters for about $10 each.  I hope to find a suitable filter , and cut a rectangle from the circular part.  The most common diameter seems to be 49 mm, but 52 and 55 mm are also available.  You might try your local camera store.  I will also try a piece of polaroid with the objective of reducing glare at the sea horizon.
    I was impressed with your calibration sights using your Bris Sextant, and I expect that those might be approximately similar for other instruments, but each would have to be calibrated individually.  The rainy season is upon us, so I have to wait for a good time, maybe even until next spring before I can get a good day.  (And I hope to be tied up to the dock!)
    Could I ask if you could measure the dimensions of your Bris Sextant, particularly the gap at the top end between the two pairs of glass and the length to the bottom apex, so that I could calculate the angle between the glass elements?  Your report of 3 bright, 4 dim and 1 very dim suggests from my tests that the angles between the two outer glasses are not the same, one perhaps twice that of the second angle.
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