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A better view of direct/retrogrades for Mercury/Venus



 
 
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Old October 23rd 18, 05:15 AM posted to sci.astro.amateur
Gerald Kelleher
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Default A better view of direct/retrogrades for Mercury/Venus

I sometimes see people scramble to put observations in proper context and that is fine,at least up to a point. The wayward video commentaries of Venus/Mercury in direct/retrograde motion are being replaced by much better descriptions although they too have difficulties -

https://www.youtube.com/watch?v=wQQN...ature=youtu.be

About 5:30 minutes in he gets around to showing how the faster Mercury appears to move from Earth and does a fairly good job up to a point but like the other guy trying to explain the annual motion of the stars falls victim to older and less productive views. Both are linked btw.

The slower moving planets and their direct/retrogrades are gauged against a fixed stellar background -

https://apod.nasa.gov/apod/ap160915.html

This doesn't apply to the direct/retrogrades of Venus and Mercury as they overtake us at the point where they are directly between the Sun and the Earth and captured by rare transits events. The background stars too have to move in a line-of-sight observation due to the orbital motion of the Earth and this is where the video commentary on the direct/retrograde of Mercury falls down in the YouTube description above (even though it should be commended).

The old Sky and Telescope website had a great animated description of all the moving components but unfortunately that video commentary is no longer available -

https://www.skyandtelescope.com/obse...3-planetdance/

It is great to see direct/retrogrades move back centre stage after their emergence 500 years ago via Copernicus. Of course a cold mind and heart doesn't have what it takes to deal with the logical reasoning but then again these things never were for those people.



 




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