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    Re: Equinoxes: when Lon=0 (or 180) but not when Dec=0?
    From: Paul Hirose
    Date: 2017 Aug 3, 12:45 -0700

    On 2017-08-01 19:18, Lu Abel wrote:
    > The Wikipedia article on the annalemma clearly labels the equatorial 
    crossings as defining the equinoxes, not the meridian  crossings.
    
    At the scale of the illustration, the Sun's declination is indeed zero
    at the equinoxes. But according to the formal definition, the equinoxes
    occur when the Sun's ecliptic longitude is 0 or 180°. E.g., see the
    Astronomical Almanac glossary:
    
    http://asa.usno.navy.mil/SecM/Glossary.html#equinox
    
    To be on the celestial equator at the time of an equinox, the Sun must
    be exactly on the ecliptic. That's virtually impossible since the Sun
    has a monthly oscillation of about one second of arc either side of the
    ecliptic.
    

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