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Offline Tumeni

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Re: Visibility of Venus, follow-on from YouTube FE video awards thread
« Reply #20 on: August 13, 2018, 05:46:47 AM »
Although the nights are shorter due to the different illuminated area of the earth on the most extreme positions, midnight is still on opposite sides of the earth from the sun, and 11pm is going to be hardly any different in either case.

As per whether the axis rotates, it is generally ridged in space. See https://en.wikipedia.org/wiki/Axial_precession

Why are you introducing the axial tilt some six months away from the date that's being considered? That has nothing to do with the photo in Morgile's video.

Again, it makes no difference what it does over time, as we're only concerned with its attitude at one instant. It can rotate all it likes the rest of the year, we're only concerned with how it was oriented on the date of the photo.

Again - what does it look like in a top-down view?
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Offline Tumeni

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Re: Visibility of Venus, follow-on from YouTube FE video awards thread
« Reply #21 on: August 13, 2018, 06:10:20 AM »

If the axial tilt is aligned with a line connecting centre of Earth and centre of Sun on both solstices, with 365 days exactly separating each occurence of the summer solstice, then what is the axial tilt pointing at approx 3 days before the solstice, when Morgile says the photo was taken? A point some 4 million miles to the left of the sun, partway between the Sun and Venus. Use a right-triangle calculator (http://www.cleavebooks.co.uk/scol/calrtri.htm) to calculate side a, subtract Sun's radius from it



That distance is 0.06% of the distance from the Sun to Venus, so, to all intents and purposes, the axial tilt is just ... only just peeking to the left of the Sun, three days prior to the solstice.




And no, NO, NO, NO - Venus and Mercury are NOT on that dotted line, not on the date of the photo in the video. They can cross that line twice a year, but Venus is certainly NOT "on that line" on the date of the photo. They may well be aligned with that line, but each will be either some distance nearer or further away than the line. Think 3D, not 2D.   Back to Reply #13, please....
« Last Edit: August 13, 2018, 06:16:05 AM by Tumeni »
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Pete Svarrior "We are not here to directly persuade anyone ... You mistake our lack of interest in you for our absence."

Tom Bishop "We are extremely popular and the entire world wants to talk to us. We have better things to do with our lives than have in depth discussions with every single curious person. You are lucky to get one sentence dismissals from us"

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Offline Tumeni

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Re: Visibility of Venus, follow-on from YouTube FE video awards thread
« Reply #22 on: August 13, 2018, 07:10:15 AM »
Night in Michigan on that date was 8h34m. From suncalc.org;

Sunset 21.20
Sunrise on 20th 05.54

"Midnight" as per Tom's diagram was therefore actually the midpoint of these two times; 01.37

The white arc represents the first half of the night, 4h17m. The observer was 1h45m past sunset, so was around 40% along this white arc, heading from left to right. Green dot shows where he was, roughly.



Venus was off to the side of the Earth-Sun axis, so must be considered as nearer to the viewer than the flat plane of the image. Need to think in 3D. It's somewhere between your eye and the Sun, and the green line is the MI observer's sightline to it.



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Pete Svarrior "We are not here to directly persuade anyone ... You mistake our lack of interest in you for our absence."

Tom Bishop "We are extremely popular and the entire world wants to talk to us. We have better things to do with our lives than have in depth discussions with every single curious person. You are lucky to get one sentence dismissals from us"

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Offline Tumeni

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Re: Visibility of Venus, follow-on from YouTube FE video awards thread
« Reply #23 on: August 14, 2018, 11:20:24 AM »
3D model. Generally-accepted RE distances of Earth and Venus from Sun are 93 million and 67 million miles. Placed model Earth and Venus 9.3 and 6.7 units away from imaginary Sun, approx two feet off my garage floor.



Placed a marker on Michigan, and aligned globe such that axial tilt points to left of Sun, and marked terminator line with string (can't use lighting to do this, or else marker won't register on photo). Aligned MI such that it is approx 1hr+ beyond sunset, beyond the terminator



White line (as per graphic above) shows MI's path through the night



Here's viewpoint from above the USA, showing MI marker on a blu-tac base, beyond the terminator



If we look from above the MI marker toward Venus, we can see the base, but this isn't looking along ground level.



Align the camera with the viewpoint of a ground-level observer, place Venus on the horizon, and we can only see the marker, not the blu-tac



Focus on the marker, instead of Venus



Again, here's the marker with the blu-tac,



And again, the blu-tac is not visible, whether focusing on Venus or Michigan.








It's hidden by the globe, proving that an observer in Michigan, over an hour beyond sunset, has a direct sightline to Venus on, or just above, the horizon.

As was photographed.
As shown in in-the-sky.org star chart.

All in accordance with this scale solar system model.
« Last Edit: August 14, 2018, 11:39:13 AM by Tumeni »
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Pete Svarrior "We are not here to directly persuade anyone ... You mistake our lack of interest in you for our absence."

Tom Bishop "We are extremely popular and the entire world wants to talk to us. We have better things to do with our lives than have in depth discussions with every single curious person. You are lucky to get one sentence dismissals from us"

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Re: Visibility of Venus, follow-on from YouTube FE video awards thread
« Reply #24 on: August 15, 2018, 03:03:57 PM »
Venus will reach its greatest elongation East two days from now, on Friday 17th.

Ideal chance for Morgile's photographer in Saginaw to grab another shot...

https://in-the-sky.org/news.php?id=20180817_11_100
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Pete Svarrior "We are not here to directly persuade anyone ... You mistake our lack of interest in you for our absence."

Tom Bishop "We are extremely popular and the entire world wants to talk to us. We have better things to do with our lives than have in depth discussions with every single curious person. You are lucky to get one sentence dismissals from us"

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Offline Tumeni

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Re: Visibility of Venus, follow-on from YouTube FE video awards thread
« Reply #25 on: August 19, 2018, 04:40:12 PM »
Venus will reach its greatest elongation East two days from now, on Friday 17th.

Ideal chance for Morgile's photographer in Saginaw to grab another shot...

No sign yet that he did. Any other empiricists out there who went planet-spotting that night? Too cloudy round my way.
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Pete Svarrior "We are not here to directly persuade anyone ... You mistake our lack of interest in you for our absence."

Tom Bishop "We are extremely popular and the entire world wants to talk to us. We have better things to do with our lives than have in depth discussions with every single curious person. You are lucky to get one sentence dismissals from us"