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    Re: Celestial predictions. was:[NAV-L] Old style lunar
    From: Alexandre Eremenko
    Date: 2004 Dec 12, 01:13 -0500

    George,
    I think you misundertood what Frank was saying.
    (I also did not understand his first message,
    but then he explained)
    
    On Sat, 11 Dec 2004, George Huxtable wrote:
    
    > >>It's no longer necessary to do this algorithmically.
    > >> Just open a  virtual
    > >>almanac page.
    
    > >From George-
    >
    > That's all very well, but in practical terms, what does a mariner,
    > given an
    > on-board  laptop, do to obtain positions by such methods
    > as Frank
    > advocates, when at sea?
    
    The mariner is supposed to download NASA database
    BEFORE she goes to sea. This database constitutes
    an almanac for several hundred years.
    THIS, of course replaces Meeus algorithm.
    
    The whole thing occupies only 10MB, which is nothing
    for a modern laptop.
    
    But I recommend to have a backup. (What if the disc crashes).
    (Or even better, to carry a spare copy of paper almanac:-)
    Much cheaper and more reliable than a spare laptop.
    
    > In practical terms, there's no requirement for position
    > accuracy to be to
    > an arc-second.
    > Meeus' algorithms do all that's necessary to obtain on-board
    > positions to quite sufficient accuracy for any maritime application, lunar
    > distances included..
    
    I suppose if you take ALL terms in Meeus you will
    also obtain 1 arcsec accuracy. But this is many hours of
    programming!
    
    I think this discussion was not about
    "practical navigator's needs".
    At least my original question was not.
    
    I just wanted to write my own long term almanac (independent
    of Frank's site, and of the web in general), partially for fun
    of doing it, partially to be able to answer all sorts of
    questions about Tiho Brahe and maybe even Hipparchus observations.
    And also to be able to reduce my balcony sights quickly.
    
    
    Alex.
    
    P.S. If I will ever do CelNav in sea, I don't want to depend
    on such a fragile device as computer for my main tool:
    the almanac.
    
    
    

       
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