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    Re: sight reduction tables
    From: George Huxtable
    Date: 2007 Sep 30, 00:54 +0100

    It was quite a pleasure to read posting [NavList 3296] by Gary LaPook, in
    favour of the HO249 tables. Well-informed, and well-argued, it was highly
    convincing. As I have stated before, I've no experience of using either
    HO229 or HO249, so have no intention of taking sides in any such debate.
    
    Indeed, I have argued over several years, on this list and others, that
    navigating by altitude sights from a small craft, in anything but the
    calmest weather, is an inaccurate business, with likely errors of a few
    arc-minutes. So I fully agree that for such a purpose, there's no need for
    sight reduction tables to be precise to 0.1 arc-minutes, and the precision
    of HO249, to no better than a whole minute, is entirely appropriate. I
    hasten to add that for observations taken from a big ship, or from on land,
    the higher precision of other tables might well be useful.
    
    And yet there's a bit of a contradiction here, it seems to me, in the
    attitude of many small-boat navigators; those who prize their expensive
    sextants, reading to 0.1 arc-minutes, and wouldn't be seen dead using a
    plastic sextant, no matter how good it may happen to be. I raise this matter
    at the risk of reopening old wounds here, but it would seem to me that if
    HO249 is acceptably accurate, then so too would be a decent plastic sextant.
    I'm not arguing against Gary here; I simply don't know whether he is a
    member of the diehard posh-sextant brigade or not. But they exist, and for
    them, would the 1-minute precision of HO249 be considered good enough?
    
    I would agree, however, that for those who wish to measure lunar distances,
    for which high precision is necessary, and (because no horizon is involved)
    possible, there's really no alternative to a metal sextant of the highest
    quality.
    
    George.
    
    contact George Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
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