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  1. What is the ecliptic longitude of the aphelion of each of the solar planets (Moon, Mercury, Venus, Earth, Mars, Jupiter, Saturn) currently in 2021 and from the observer's point of view on the earth? Please note I don't want to know their distances from the sun at their states of aphelion but their locations on the ecliptic while they are in aphelion states.

  2. Does earth's axial precession cause the ecliptic longitude of planets' aphelions to change?

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    $\begingroup$ I don't understand what you mean the aphelion of the moon. The moon is a satellite of the Earth. $\endgroup$
    – James K
    Aug 18 at 14:53
  • $\begingroup$ The heliocentric ecliptic longitude & latitude is fairly easy to calculate, but the geocentric is rather messy. $\endgroup$
    – PM 2Ring
    Aug 19 at 8:53
  • $\begingroup$ However, it doesn't make sense to calculate the geocentric ecliptic coords of the Earth. $\endgroup$
    – PM 2Ring
    Aug 19 at 8:57
  • $\begingroup$ The axial precession causes the whole geocentric ecliptic coordinate grid to "wobble", but that has a period of ~26,000 years. On a much shorter time scale, for points inside the Solar system, there's parallax due to Earth's annual motion around the Sun. $\endgroup$
    – PM 2Ring
    Aug 19 at 9:05

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