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    Re: Calibrating a sextant scale
    From: Bill Morris
    Date: 2007 Nov 24, 20:03 -0800

    On Nov 25, 12:43 pm, "George Huxtable" 
    > Alex wrote-
    > Not sure that it was me, though it was a good question. I would like to ask
    > some supplementary questions.
    > Has anyone on this list, by measuring star-star distances or by any other
    > method, ever discovered reproducible errors, outside the terms of a
    > calibration certificate or maker's warranty, in a sextant? Has anyone made
    > calibration measurements of his own, in which he has more confidence than in
    > the manufacturer's scale readings, corrected as necessary by the box
    > certificate? And if the answer is yes, what's the magnitude of those errors?
    > =====================
    >I am in the process of doing so by two methods. One uses two collimators 
    aligned using a second-order theodolite. The other will use two 
    autocollimators, a largish(600 x 900) surface plate and a plane mirror. Using 
    the first method I will compare a Pioneer-Bendix Mk II with an SNO-T and 
    using the second, those two sextants and a MkIX bubble sextant. I will report 
    to the list in a week or three. The first method is very tedious. The second 
    promises to be so. So far I have discovered some differences from the 
    certificates or claimed accuracy, of up to 0.4 arc-min, but it's early 
    Bill Morris
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