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    Re: Impossible lunar example
    From: George Huxtable
    Date: 2010 Aug 29, 13:46 +0100

    Antoine, quite rightly, questioned my statement that the date of the 
    observation referred to in the attachment "moore p45.jpg" was Nov 10th 
    1796, whereas he had taken it to be 20th Nov. My misreading was based on an 
    over-hasty glance at the screen, which was none-too-clear, and I've been 
    back to look closer at the original, which certainly states the 20th. Sorry 
    for adding unnecessary complexity to an already complicated matter.
    
    Further down, he wrote-
    "as regards the time of 6:10 PM read on the W009° meridian, and given it is 
    a "local time"..."
    
    The time was given as "6:10 pm per watch well regulated". So I don't think 
    it could be a local time, adjusted according to the position of the ship at 
    that moment. To follow that, its hands would have to be frequently shifted 
    to correspond to any assessed changes in longitude, by 4 minutes for each 
    degree. This would be contrary to the "well-regulated" description. I 
    suggest, then, that the watch was intended to follow Greenwich time, but 
    whether this was mean or apparent time is unclear to me.
    
    Antoine honours Nevil Maskelyne as "Sir Maskelyne", which I'm sure would 
    have been richly deserved, but he received no such title. He was the 
    Reverend Nevil Maskelyne, Doctor (of divinity), FRS. Of these, the last, 
    his fellowship of the Royal Society, was no doubt most most appreciated by 
    him.
    
    Antoine is looking for a "one-figure typo" to explain the impossible lunar, 
    but perhaps he will be convinced otherwise by additional examples, in that 
    second edition of Tables requisite", which I will mention in another 
    posting.
    
    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.
    ----- Original Message ----- 
    From: "Antoine Couette" 
    To: 
    Sent: Sunday, August 29, 2010 9:42 AM
    Subject: [NavList] Re: Impossible lunar example. was: Short-cut lunars. 
    was: Clearing lunars
    
    
    Dear George,
    
    
    
    In reply to your lehghty reply about trying to reckon the time of the 
    "impossible lunar" into our current UT / Date times cale:
    
    - First of all, thank you very much for your very detailed insights,
    
    - I had come to the conclusion that at @6:10 p.m. in late november, there 
    is no way for the Sun to be seen at a height of some 17° anywhere on the 
    Greenwhich W009° Meridian.
    
    - So, and by respect to Sir Maskelyne, I am making the assumption that 
    there is a "one figure typo" (and just one figure) in our quoted example, 
    with the typo error originating not from Maskelyne himslef, but from 
    somebody else.
    
    There could be a typo in :
    
    - the date of the month, not the month itself since it is in full letters, 
    or
    
    - one of the quoted heights (probably in the leftmost digit, i.e. the one 
    multiple of 10), or
    
    - the quoted Longitude, or
    
    - the quoted Distance (some doubt here), or
    
    - the quoted year.
    
    This is a fairly lenghty list, but it can be worked out.
    
    From what I can read, this Lunar took place on November 20, 1796 at 6h10 PM 
    from a place located on the Greenwhich W009° meridian.
    
    So, my question is twofold - and anybody else, please feel free to reply - 
    :
    
    - do the numbers I read look the same to you ? I am not sure since you 
    quoted a date ot Nov 10th, while I can read Nov 20 th,  and
    
    - as regards the time of 6:10 PM read on the W009° meridian, and given it 
    is a "local time", it shows as 6:46 PM Greenwhich Time - which makes 
    sense - (see one of your documents).
    
    So, I just need to know whether this time/date of Nov 20, 1796 , 06:46 PM 
    Greenwhich (true) time would translate to-day into Nov 20, 1796 with a UT 
    value approximately equal to "18:46 + Equation of Time".
    
    As long as I can have an approximate UT time to +/- 30 minutes as reckoned 
    by to-day standards( and I do NOT think it is necessary to add/substract 
    again any extra 12 hour value) and as long as I know that the actual date 
    would be Nov 20, 1796 by to-day reckoning standards (no need to add 
    substract one day, no ? ), I am happy.
    
    So I just need confirmation that the date and hour I read and I am 
    reckoning into our current time scale system are not subject to any gross 
    and systematic error.
    
    (not easy somtimes to make one self clear to others ...)
    
    Thank you and
    
    
    Best Regards
    
    Antoine
    
    
    
    
    
    
    
    
    
    
    
    
    
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