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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Dec on equinox day
From: Bela Kovacs
Date: 2025 Mar 23, 06:31 -0700
From: Bela Kovacs
Date: 2025 Mar 23, 06:31 -0700
Dear all,
I have attached the diagram from the IMCCE page.
https://www.imcce.fr/lettre-information/archives/221#current-article5
I am trying to understand why the Sun has an ecliptic latitude. Is it some kind of parallax?
The Earth-Moon barycenter is 4671 km from the center of the Earth, the (mean) inclination of the Moon's orbits is 5.145°. The distance of the barycentre from the plane of the ecliptic coordinate system is 4671*sin(5.145) = 418.8792 km
The mean Sun-Earth distance is 149*10^6 km.
atan(419 / 149*10^6) = 0.58"
This is close to the value in the diagram on the IMCCE page (0.7").
Is this a good direction to understand the problem?
Thank you,
Bela
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