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    Re: Equinoxes: when Lon=0 (or 180) but not when Dec=0?
    From: Bill B
    Date: 2017 Aug 1, 15:53 -0400

    On 7/31/2017 9:08 AM, Tony Oz wrote:
    "Why the definition of Equinoxes demands the Sun's longitude to be equal
    to either 0° or 180°?
    
    The actual length of the day or night depends directly on the Sun's
    declination (rather than on its' longitude), so why not Dec == 0° then?
    
    Yes, I know that the orbital plane (of Earth) wobbles a bit (because of
    other planets' gravitation), but it is immediately translated into Sun's
    apparent declination, so I'm puzzled. Is it just for the simplicity of
    calculations (of the equinox of date)?"
    
    Perhaps the attached will help. Courtesy of Herbert Prinz, March 2006
    
    

    File: 139659.equinox.doc
    File:


       
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