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    Re: Time of meridian passage accuracy
    From: George Huxtable
    Date: 2009 Sep 25, 21:46 +0100

    I just wrote-
    
    "On the 29th April, the Sun's declination is increasing (Northward) by about
    0.8 arc-minutes per hour. By a bit of rough guesswork, that's enough to
    delay the moment of peak altitude, to be somewhere between 1 and 2 minutes
    later than Meridian Passage. Which will throw out his assessments by that
    amount."
    
    However, that guesswork was a bit too rough. On second thoughts, I would
    reassess that time offset, due to changing declination of the Sun, to be
    about half a minute of time. Still well worth correcting for, however.
    
    George.
    
    contact George Huxtable, at  george{at}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: "George Huxtable" 
    To: 
    Sent: Friday, September 25, 2009 9:23 PM
    Subject: [NavList 9927] Re: Time of meridian passage accuracy
    
    
    |
    | Throughout his posting [9923], Douglas Denny appears to presume that
    | Meridian Passage of the Sun occurs at the same moment as the maximum
    | altitude of the Sun, at the peak of the curve of altitude with time.
    |
    | But it doesn't, except at the solstices, because of the Sun's changing
    | declination. On the 29th April, the Sun's declination is increasing
    | (Northward) by about 0.8 arc-minutes per hour. By a bit of rough
    guesswork,
    | that's enough to delay the moment of peak altitude, to be somewhere
    between
    | 1 and 2 minutes later than Meridian Passage. Which will throw out his
    | assessments by that amount.
    |
    | To set up a precise North-South line, it's a factor that must be allowed
    | for. For star observations, there's no such problem, as the declination
    | stays constant.
    |
    | George.
    |
    | contact George Huxtable, at  george{at}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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