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    Re: Impossible lunar example. was: Short-cut lunars. was: Clearing lunars
    From: Kent Nordstr�m
    Date: 2010 Aug 28, 13:12 +0200

    Hi,
    George mentions that the 1780 issue of the Tables Requisite isn't scanned
    into Googles. I believe that the edition should be 1781, which is available
    on Googles. Further, my understanding is that there is no edition published
    in the time span 1767 to 1781.
    Best regards,
    Kent N
    
    --------------------------------------------------
    From: "George Huxtable" 
    Sent: Saturday, August 28, 2010 12:42 PM
    To: 
    Subject: [NavList] Impossible lunar example. was: Short-cut lunars. was:
    Clearing lunars
    
    > Antoine asked-
    >
    > "And Last note, could one of you please publish the original data of your
    > earlier quoted "impossible Lunar"."
    >
    > With pleasure, Antoine, as far back as I can.. The information was in the
    > attachments to my posting of 25 August, threadname "clearing lunars", and
    > here it is again.
    >
    > Sorry that one of the pages is pretty fuzzy, but I think it can just about
    > be deciphered.
    >
    > The Janet Taylor text is from her "Luni-solar and horary tables", of 1833,
    > fully available on Google Books.
    >
    > About this, I wrote-
    >
    > | Looking through some
    > | examples of her method for clearing lunar distances, she has in some
    > cases
    > | compared her results with those given, for a similar problem, by John
    > | Hamilton Moore, in his "Practical Navigator". My eye fell on her
    > "Example
    > | 3" on page 40, about which her words are attached, as "Taylor Luni-solar
    > | p40".
    > |
    > | Those words intrigued me. They refer, as stated on another page, to
    > Moore's
    > | 10th ed. I took a look at what Moore said. His "Practical Navigator",
    > too,
    > | is available on Google, in his 11th ed. of 1795, and I attach the
    > relevant
    > | passages (using Lyons' and Witchell's methods), from pages 245 and 252.
    > |
    > | And indeed, Janet Taylor has got it absolutely correct. Moore has set
    > | himself a quite impossible example. With the altitudes that he has given
    > | for the two bodies, there isn't nearly enough spacing across the sky, in
    > | any possible geometry, to achieve such a large value of lunar distance.
    > | It's a contrived example, that can't possibly happen in real life. Yet
    > he
    > | has gone blindly through the motions of making the corrections to clear
    > | that absurd value, by two different methods, and indeed, got the same
    > | result in each case.
    > |
    > | Much of the impact of Taylor's point, made in 1833, is however lost,
    > | because that mistake occurred  some 38 years earlier. By the time
    > Moore's
    > | 18th edition of 1810 (also on Google) had appeared, that erroneous
    > example
    > | had been dropped.
    >
    > Since then, Frank has pointed out that the same impossible problem was
    > presented, earlier still, by Maskelyne, in his "Tables Requisite" of 1780,
    > but that edition isn't scanned on Google. Unlike other editions, which
    > are,
    > but omit that problem. So I can't quote Maskelyne's original version.
    > Perhaps Frank has a copy.
    >
    > George.
    >
    > contact George Huxtable, at  george@hux.me.uk
    > or at +44 1865 820222 (from UK, 01865 820222)
    > or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    >
    
    
    
    

       
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