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    Calibrating a sextant scale
    From: Mike L
    Date: 2007 Nov 20, 03:33 -0800

    Whilst it is easy to calibrate a sextant's zero reading, is there any
    way to calibrate any other readings?
    My thought was to lean over a cliff and view my own reflection, and
    then align the mirror with the horizon, this should be somewhere close
    to 90deg (give or take the variation of the horizon from horizontal).
    Having established the true 90degree, the 45degrees could be
    calibrated by finding two objects precisely 90degrees and finding an
    object exactly halfway between.
    Then it occurred to me that I could use a bucket of water at the
    seaside, to give two readings (direct and false horizon) one being
    exactly** twice the other.  (** allowing for known errors)
    at which I've just realised that star charts are far easier .....
    but it might amuse others to think about leaning over a cliff!
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