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    Re: Lunar Distance in Wikipedia
    From: George Huxtable
    Date: 2007 Jul 23, 09:55 +0100

    
    I had quoted the Wikipedia entry on Lunar Distance (Navigation) as-
    
    "[edit] Theory
    If there are two people, one at Greenwich and one 15 degrees West, the time
    by the sun will be one hour later at 15 degrees West. So, if the person
    observes the position of the moon at Greenwich at noon and another person
    observes the moon 15 degrees west of Greenwich at their locally determined
    noon, then due to the one hour difference, although the sun is at its
    zenith, the moon would have moved approximately its own diameter across the
    sky."
    
    and Frank replied-
    
    | The explanation as it stands is not literally incorrect. It's just
    | muddled and confusing. What that author is saying is that if I measure
    | the Sun-Moon lunar distance at my local noon, and another observer,
    | who by design is 15 degrees in longitude west of me, measures the Sun-
    | Moon lunar distance at his local noon, then because local noon occurs
    | an hour later, the Sun-Moon lunar distance will have changed by about
    | half a degree (the cleared distance, that is).
    
    Response from George-
    
    It seems to me that it really is literally incorrect, and in more ways than
    one: not "just" muddled and confusing.. If the author had said what Frank
    says he was saying, then there would be no argument about it. But he didn't,
    though that may be what he intended to convey. There's no way in which the
    time-by-the-sun, at 15 degrees West, can possibly be one hour later than it
    is at Greenwich.
    
    An additional error, which I first missed, but which Frank avoids in his
    rewording, is the statement that "due to the one hour difference ... the
    moon would have moved approximately its own diameter across the sky". It
    doesn't, of course. Like every other body near the ecliptic, the Moon moves
    about 15 degrees "across the sky" in any hour. It's with respect to the Sun,
    and the (invisible) star background, that the Moon moves by approximately
    its own diameter.
    
    Thanks to Frank for pointing out the serious abuse of the word "zenith";
    another point I had missed on first reading.
    
    Frank ended-
    
    "Some of the articles are
    | maintained by informal teams of experts, and their articles are
    | excellent. Some of the articles are barely maintained at all, and the
    | content can be amateurish."
    
    Well, what about that as a little project for NavList, then? As an "informal
    team", we may be in as good a position as anyone else to agree a better
    explanation, between us, than the one that is presently posted. Anyone like
    to offer a first shot, to be kicked around by the group? To be a Wikipedia
    entry for "Lunar Distance (navigation)", that goes in under the NavList
    name, to give it (and us) a bit of credibility.
    
    There may well be other material, in the context of navigation, to which we
    could make some contribution, between us.
    
    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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