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    Re: Lewis and Clark lunars: a request for help.
    From: George Huxtable
    Date: 2004 Apr 8, 23:26 +0100

    Frank Reed commented as follows-
    
    >George H wrote:
    >"For the lunartics on this list, here's something of a challenge (and others
    >should switch off now). What will be required is a computer-program that can
    >calculate positions of bodies in the sky back to 200 years ago."
    >
    >And several people replied to George with suggestions for software that he
    >might use, but I don't think that's what he was trying to say. Software to do
    >this is widely available. George, I am nearly certain, already has access to
    >software that does these calculations. I believe he was trying to say that
    >if any
    >of the list's lunatics wanted to work on this problem that *they* would
    >require software capable of calculating positions of heavenly bodies in 1803.
    
    =========================
    
    Frank has understood what I'm after, precisely.
    
    My own calculations were based on a home-brewed program, based on Meeus,
    which runs on a programmable calculator.
    
    This investigation requires that EVERYTHING be looked at with a leary eye,
    including that program. I have some confidence in the numbers my program
    comes up with, after comparing its prediction with a lunar distance in the
    1803 almanac, and finding that they agree within an arc-minute. If someone
    is brave enough to calculate this L&C longitude for themselves, the more
    independent it is of my own calculation, the more likely it will be to
    uncover an error somewhere.
    
    When I said-
    "What will be required is a computer-program that can calculate positions
    of bodies in the sky back to 200 years ago."
    I meant that such a program would be a necessary tool for anyone who tried
    to recalculate these lunars.
    
    There's an alternative to that computer program, however, which is to do
    what L&C had to do, and work it all out using the predictions in the 1803
    Nautical Almanac. I have copied down the relevant entries from that
    Almanac, from a copy in the library, and if anyone asks I will cheerfully
    transcribe that information in a posting. Bruce Stark has kindly contacted
    me off-list to offer to photocopy the relevant pages from his own 1803
    Almanac, if another listmember would offer to post them up somehow, and
    this could be a better alternative still. Note that taking this 1803
    Nautical Almanac route implies that times have to be specified in Greenwich
    Apparent Time, not Greenwich Mean Time (the difference being the "Equation
    of Time").
    
    I should acknowledge a text mistake in that last posting , which anyone who
    tries to implement it is likely to notice straightaway. In analysing their
    equal-altitude obs., I started a paragraph with "Now the times 1, 2, 3 can
    be averaged, and also, 3, 4, and 5." It should have read, of course, "Now
    the times 1, 2, 3 can be averaged, and also, 4, 5, and 6.". Sorry about
    that.
    
    Thanks for the helpful responses, off-list and on-list, which show that
    many listmembers have taken my problem seriously. Please keep them coming.
    
    Yours, George.
    
    ================================================================
    contact George Huxtable by email at george---.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ================================================================
    
    
    

       
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