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    Re: Halley's lunar knowledge.
    From: George Huxtable
    Date: 2007 Nov 25, 21:09 -0000

    Oh dear. I seem to have got up Mike Daly's nose once again.
    
    He writes, indignantly-
    | I don't know why you persist in misquoting or convoluting the meaning of
    | my statements.  I wish you would stop, as it contributes nothing to the
    | discussions.
    
    I had quoted him as saying-
    
    | > "Halley's method can only be as accurate as his lunar position
    knowledge.
    | >   No one published tables at that time (as Maskelyne did after 1767).
    | > There was the raw data that was coming out of Flamsteed's observations
    | > and other observers that may have been accumulating data.  Newton and
    | > Halley published Flamsteed's data without his permission in 1712 but
    | > what Halley used in the 1699 timeframe I don't know offhand."
    
    and replied-
    
    | > Anyway, the question arises; how did Halley predict Moon positions?
    There
    | > were indeed tables published of the Moon, contrary to Mike Daly's claim
    | > above, but these were nothing like as precise and detailed as Maskelyne
    | > derived from Mayer in 1767. They dated back to Ptolemy! Intended for
    | > astrologers, rather than astronomers.
    
    and he protests-
    | Exactly how is what I wrote contrary to what you write?  There was no
    | Nautical Almanac of reduced lunar data but there was raw data on lunar
    | position.  That's what I wrote and that's what you wrote.
    
    and for some reason he pointed to an anonymous contemporary review of
    Halley's Southern-stars catalogue. I don't understand its relevance, but am
    grateful for that mention, as I had not seen it before.
    
    ==================
    
    But we need to examine Daly's words, that he complains have been misquoted
    or convoluted; I'm not certain which. These were-
    "No one published tables at that time (as Maskelyne did after 1767)." and
    then went on to refer to "raw data".from Flamsteed and others
    
    Well, now he is playing with words. Lunar position tables WERE available at
    the relevant date, particularly in the French "Connaissance du Temps",
    giving lunar ecliptic longitude and latitude for each day, with respectable
    accuracy. Similar tables had been printed, with varying levels of
    inaccuracy, right back to the beginning of printing, Regiomontanus in 1474.
    
    If he had meant "No one published LUNAR DISTANCE tables at that time", he
    should have said that. But he was discussing Halley's lunar POSITION
    knowledge. As Halley took no interest in observing lunar distances at sea,
    and required only lunar positions, then only lunar positions were relevant
    in the context; not lunar distances. And those lunar positions WERE
    available at the time from other sources, if with somewhat less precision
    than were Maskelyne's. Are those what Daly appears now to dismiss as "raw
    data"?
    
    If Mike Daly doesn't make his meaning clear, he will get misunderstood.
    
    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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