On Tuesday, October 16, 2018 at 1:34:02 AM UTC+1, palsing wrote:
On Sunday, October 14, 2018 at 1:32:08 PM UTC-7, Gerald Kelleher wrote:

The illusory loops (direct/retrograde motion) of the slower moving planets seen from Earth are distinguished from the actual loops (also direct/retrograde motion) of the faster moving Venus and Mercury closer to the Sun....

Apparently, you are *still* too uneducated to understand that both Mercury and Venus, in fact, *DO* perform illusionary loops WRT the background stars, in addition to the big swoopy loops they make WRT the Sun and the horizon. Take a good look at these...

https://www.youtube.com/watch?v=Nv-ZPxf07ks

https://www.youtube.com/watch?v=FtV0PV9MF88

https://www.youtube.com/watch?v=IYYwNvjr7Lg

Pretty cool, isn't it?

Those demonstrations are all nonsense but most people who actually enjoy astronomy know that already. The lead in to the actual loops of Venus and Mercury ,at least when showing students, is perhaps showing how the satellites Jupiter run their circuits around their parent planet and then applying the same principle to the faster Venus in a smaller orbital circumference seen from a slower moving Earth -

https://www.youtube.com/watch?v=zqZEgoJasPQ&t=95s

https://www.popastro.com/images/plan...ary%202012.jpg


All the pieces fit together, the size increase, the reason the phases prevent Venus from becoming appreciably brighter as it approaches close to the Earth in our common solar orbit, the back and forth motion of the planet against the background stars as it moves in front of the Sun and then in the opposite direction behind the Sun.

The most important feature is found in the transition from left to right of the Sun or from an evening to morning appearance (and back again) as transits signify the point at which Venus is closest to us while overtaking our planet with the central Sun as a backdrop -

https://www.youtube.com/watch?v=4Z9rM8ChTjY&t=39s


When applied to the stars, the transition from an evening to morning appearance is proof of the Earth's orbital motion while setting the Sun up as a central reference for the motions of Venus and Mercury so their direct/retrograde motions are just a consequence of seeing them move directly around the Sun and not an illusion.

The first Sun centred astronomer were enthusiastic about the resolution of direct/retrogrades of the slower moving planets but were unsure as to how to treat Mercury and Venus. Despite all the technological and imaging advances, I see no enthusiasm for the separate perspective which deals with the direct/retrogrades of Venus and Mercury despite some people actually knowing most of what goes into the resolution. All in its own time as far as I am concerned.