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Astronomy Picture of the Day - Afternoon Analemma
NASA ^ | 23 Sep, 2023 | Image Credit & Copyright: Ian Griffin (Otago Museum)

Posted on 09/23/2023 11:55:35 AM PDT by MtnClimber

Explanation: An analemma is that figure-8 curve you get when you mark the position of the Sun at the same time each day for one year. To make this one, a 4x5 pinhole camera was set up looking north in southern New Zealand skies. The shutter was briefly opened each clear day in the afternoon at 4pm local time exposing the same photosensitized glass plate for the year spanning September 23, 2022 to September 19, 2023. On two days, the winter and summer solstices, the shutter was opened again 15 minutes after the main exposure and remained open until sunset to create the sun trails at the bottom and top of the curve. The equinox dates correspond to positions in the middle of the curve, not the crossover point. Of course, the curve itself is inverted compared to an analemma traced from the northern hemisphere. And while fall begins today at the Autumnal Equinox for the northern hemisphere, it's the Spring Equinox in the south.


TOPICS: Astronomy; Astronomy Picture of the Day; Science
KEYWORDS: analemma; apod; astronomy; nasa; science
To be added or removed from the Astronomy Picture of the Day ping list please send me a request via "Private Reply" (Mail).

For more detail go to the link and click on the image for a high definition image. You can then move the magnifying glass cursor then click to zoom in and click again to zoom out. When zoomed in you can scan by moving the side bars on the bottom and right side of the image.

1 posted on 09/23/2023 11:55:35 AM PDT by MtnClimber
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To: MtnClimber

2 posted on 09/23/2023 11:56:04 AM PDT by MtnClimber (For photos of Colorado scenery and wildlife, click on my screen name for my FR home page.)
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To: MtnClimber

if the pic is takin the same time every day, I’m wondering why the spuratic locations of the sun in the sequence... has the earth aquired a “misfire” in its spinning engine!?? wonder why we didnt feel it!


3 posted on 09/23/2023 12:00:04 PM PDT by sit-rep
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To: sit-rep

Camera set up...jostle?


4 posted on 09/23/2023 12:06:10 PM PDT by goodnesswins ( We pretend to vote and they pretend to count the votes.)
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To: 21stCenturion; 21twelve; 4everontheRight; abb; AFB-XYZ; AFPhys; Agatsu77; America_Right; ...
Pinging the APOD list.

🪐 🌟 🌌 🍔

I don't like the photos that are not NASA photos because NASA photos are great. At least this non-NASA photo is not muslim fluffing or china fluffing from the woke communists that run our government at this time. May pestilence infect their communist private parts and may they eventually find themselves against the wall...Amen.

5 posted on 09/23/2023 12:08:00 PM PDT by MtnClimber (For photos of Colorado scenery and wildlife, click on my screen name for my FR home page.)
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To: sit-rep

The figure eight is caused by the tilt of the earth in the orbit around the sun. The same pattern is seen in geosynchronous satellites which have slightly inclined orbits (orbatil tilts), except the figure eight pattern is daily and not annually.


6 posted on 09/23/2023 12:19:46 PM PDT by MtnClimber (For photos of Colorado scenery and wildlife, click on my screen name for my FR home page.)
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To: MtnClimber
The earth's orbit doesn't wobble, so what causes this? Sometimes I wonder that, but other times I think "who cares?"




7 posted on 09/23/2023 12:21:31 PM PDT by Telepathic Intruder
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To: Telepathic Intruder

The Earth’s orbit does not wobble, the poles are at an angle to the sun where the north pole is angled toward the sun on one side of the orbit and angled away from the sun on the opposite side of the orbit.

That galaxy photo is probably a disruption from another galaxy passing nearby, not normal orbital dynamics.


8 posted on 09/23/2023 12:30:12 PM PDT by MtnClimber (For photos of Colorado scenery and wildlife, click on my screen name for my FR home page.)
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To: MtnClimber

Yes, the galaxy is easy to understand. The Analemma not so much. But alright, thanks.


9 posted on 09/23/2023 12:36:13 PM PDT by Telepathic Intruder
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To: Telepathic Intruder

According to some reading I did years ago the earth wobbles on its axis. Could that be the cause?

Side note: Neither the rotational speed nor the orbital speed and distance are constant, as well. Some things to think about regarding “human-caused” global warming, IMHO.


10 posted on 09/23/2023 12:51:23 PM PDT by Ignatz (Winner of a prestigious 1960 Y-chromosome award!)
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To: Ignatz

No, the earth’s precession is a 25,000 year cycle. That means Polaris will no longer be the north star is a few thousand more years. But I think Mtn did a good explanation in post #8. It’s actually not that complicated.


11 posted on 09/23/2023 12:55:22 PM PDT by Telepathic Intruder
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To: MtnClimber

Great explanation! I’ve better examples of an analemma, but this one is basically the same as any others I have seen. It does take determination and patience to pull it off.


12 posted on 09/23/2023 1:04:34 PM PDT by telescope115 (I NEED MY SPACE!!! 🔭)
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To: MtnClimber

I new about the figure 8... i’m curious as to why there are different spaces between the suns... could the earth spin slower and faster on certain days??


13 posted on 09/23/2023 1:24:40 PM PDT by sit-rep
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To: MtnClimber

indeed it does wobble over a year. the north pole tips towards the sun when its furthest away in the summer and in the winter, 3 million miles closer to the sun, the north pole tips away from the sun... hence the reason for tropic of cancer, tropic of capricorn...


14 posted on 09/23/2023 1:32:56 PM PDT by sit-rep
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To: goodnesswins

could be!! that could very well be a tectonic plate shift!! lol...


15 posted on 09/23/2023 1:34:00 PM PDT by sit-rep
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To: sit-rep

The earth’s spin remains constant, but its orbital speed does not. It slows down near aphelion, and speeds up near perihelion. That also explains why the figure 8 is bigger at one end. See, I’m starting to think about it now. If I’m wrong sue me. Get your people to talk to my people and come to some financial arrangement.


16 posted on 09/23/2023 1:38:05 PM PDT by Telepathic Intruder
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To: Telepathic Intruder

I’m calling Saul!!


17 posted on 09/23/2023 1:50:42 PM PDT by sit-rep
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To: sit-rep
i’m curious as to why there are different spaces between the suns

Gaps in the "suns" are caused by cloudy days when the sun wasn't visible!

18 posted on 09/23/2023 2:12:53 PM PDT by plsvn
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To: plsvn

now THAT is believable!! I’ll sit back content with that answer!!


19 posted on 09/23/2023 2:28:33 PM PDT by sit-rep
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To: sit-rep
The shutter was briefly opened each clear day…

Some days aren’t “clear” so no exposure was taken?

20 posted on 09/23/2023 3:20:04 PM PDT by immadashell (Save Innocent Lives: Ban Gun Free Zones)
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