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    Re: Horizontal distance off measurements
    From: Peter Fogg
    Date: 2003 Mar 26, 09:44 +1100

    Thanks to Doug Royer for taking the trouble to explain in detail his
    technique for horizontal sextant readings to measure distance off. I
    intend to print it out and work through his example in the hopes of
    better understanding it.
    If I remember correctly the promise which led here was that horizontal
    sextant readings would be more accurate than taking bearings with a hand
    held compass, which is something I do a lot while cruising along the
    coast. Typically the target, due to boat movement, swings from side to
    side through the eyepiece and what I have to judge is the midpoint of
    the average swings. I don�t expect that it is more accurate than to the
    nearest few degrees but 3 of them typically yield a tight enough
    triangle, often enough confirmed by GPS reading.
    Sure a sextant can measure to less than one minute of arc but I�m not
    sure how practical this would be on a small boat in average coastal
    conditions;  about 1-2 metres of swell. I suspect Doug is talking from
    the perspective of a big stable ship which could be quite different.
    Still, its all useful grist to the mill of knowledge.  Contributions
    like this are much appreciated and I wouldn�t, in his shoes, take too
    seriously the occasional acerbic comments the list throws up.

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