The observation of a planet incorporates many features, not just their wandering motion against the direct motion of the Sun through the ecliptic plane but also the variations in the time they took to make a circuit of the constellations, at least in the
Ptolemaic framework-
" Moreover, we see the other five planets also retrograde at times,
and stationary at either end [of the regression]. And whereas the Sun
always advances along its own direct path, they wander in various
ways, straying sometimes to the south and sometimes to the north; that
is why they are called "planets" [wanderers]. " Copernicus
This immediately removes many contributors who rely on the more recent RA/Dec framework as they assign a wandering motion to the Sun also and at variance to the working principles of the first Sun-centred solar system researchers.
http://astro.dur.ac.uk/~ams/users/solar_year.gif
I would have really nothing to say about the debacle which attempted to isolate a planet by size as it is best consigned to an indulgence by those who tried to conjure an imaginary problem into existence and made it worse for everyone and an awful
dishonour to our era.
The wandering motions of the planets can now be accounted for in two distinct ways depending on whether the planets are moving faster or slower than the Earth in a Sun-centred system.
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