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    Re: When did the Atumnal Equinox occure this year?
    From: Peter Hakel
    Date: 2019 Sep 27, 15:51 -0700

    Hi Brad,

    Yes, I looked at them; Paul’s results (and underlying models) are much more detailed and I am glad that mine (which are based on Jean Meeus’s book) are good enough for celestial navigation purposes.

    In fact, I just received the 2020 Commercial Edition of the Nautical Almanac. Every year at about this time I do spot comparisons between my spreadsheets and this almanac to make sure that the spreadsheets remain accurate enough for the next year. For now, I only peeked at the 2020 autumnal equinox; the almanac lists Sun’s declination on September 22, 2020 as:

    N 0° 00.5’  at 13h UT
    S 0° 00.5’  at 14h UT

    which is consistent with sun.xls placing the Sun on the equator at about mid-hour, so I am feeling optimistic. :-)

    The same argument applies to small differences in delta T mentioned by Dave Walden; I use this fit:
    https://eclipse.gsfc.nasa.gov/SEhelp/deltatpoly2004.html


    Peter Hakel
    35° 53’ N
    106° 19’ W

       
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