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    Re: Today’s the Spring Equinox
    From: Paul Hirose
    Date: 2019 Mar 25, 15:53 -0700

    An eclipse has duration but an equinox does not, since it's the instant
    when the Sun geocentric apparent ecliptic longitude is 0 or 180.
    Declination, right ascension, and ITRS (geodetic) latitude pass through
    zero (or 12 hours) near every equinox, but none of those events is the
    true equinox. Nevertheless, zero geodetic latitude is a reasonable
    definition for a non-technical audience, since otherwise you have to
    explain ecliptic longitude.
    
    2019 March 20
    
    21:57:47 UTC zero dec
    21:57:58 UTC zero ITRS lat
    21:58:26 UTC * zero ecliptic lon
    21:58:33 UTC zero RA
    
    * correct time of equinox
    
    JPL DE431 ephemeris, IAU 2006 precession, and 2000B nutation. Polar
    motion x = 0.0438", y = 0.3704". I did the computation a month or two
    before the equinox and so the polar motion parameters are a little
    different from the final values determined by the IERS.
    
    Unfortunately, the IMCCE was not equally clear about the basis of their
    super precise determination that the equinox occurred at 21:58:27.05
    UTC. I have not been able to duplicate that.
    

       
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