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    Re: Plumb-line horizon vs. geocentric horizon
    From: Pierre Brial
    Date: 2005 Feb 10, 16:33 +0400

    > Frank Reed a ?crit:
    > In the water off-shore of Reunion, there should also be a deflection
    > (diminishing rapidly with distance) and 0.7' would be observable,
    > though with difficulty, using a standard sextant. Have you had any
    > opportunity to use your sextant at sea?
            Not yet. My sextant has a mechanical accuracy of 0.2', but despite the
    fact I have adjusted it, repeated tests on star distances show me that
    it is difficult to have a practical accuracy of under 0.8'. But may be
    this is also because of my lack of experience or inaccuracies in my eye.
            With horizon measurement, taking into account the deflection seems
    difficult as the deflection will be different on the spot and on the
    horizon. I fear this will cause hair-raising computation.
            To simplify, may be you could evaluate the difference of geoid height
    above the ellipso?d on your place and on the horizon, and add this
    difference to the eye height for your computation.
    > Speaking of Reunion, the famous navigator, Nathaniel Bowditch, visited
    > Reunion on one of his earliest ocean voyages. According to Berry, his
    > biographer, Bowditch spent five months there. His logbook and other
    > notes from this trip are still in existence.
    Are these notes available somewhere ? Foreign accounts on Reunion for
    18th century are not well known here...
    > Bowditch found the French
    > women of the island scandalous and wrote "they are too bold... nothing
    > puts them to the blush". They embarassed him by exposing their legs
    > (happy mardi gras, everybody). That was in 1795.
    err.. things have not changed ...
    Pierre Brial

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