Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Equinox, eggs and other questions
    From: Herbert Prinz
    Date: 2002 Mar 16, 20:31 +0000

    The astronomical definition for equinox is "The instant at which the
    apparent longitude of the Sun is 0deg (or 180deg)". This may or may not be
    the moment at which the declination of the Sun is 0 deg. The reason being
    that the latitude of the sun need not be 0 (this year it will be 0.06" at
    time of equinox) and that the Earth is wobbling around a little.
    According to MICA, the next equinox will be on Mar 20 at 19:17:12 ET.
    Assuming 64 seconds for delta T this gives 19:16:08 UT. However, the Sun
    will have crossed the equator 4 seconds earlier than this.
    This subtle difference is of no significance to the navigator, but it is of
    utmost importance to Rob Gendreau, who would miss the proper moment at which
    to balance his eggs, if he followed an official ephemeris.
    Rob Gendreau wrote:
    > I always assumed the equinox was when the sun crossed the equator, but
    > since taking a Cel Nav class I realize my naivete, and now assume that it
    > must be more complicated than that ;) For instance, is it when the center
    > of the sun crosses, or the lower limb, or what?
    > Tradition has it that at the moment of the equinox you can stand an egg on
    > end. So an accurate time for the equinox is essential.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site