APOD: Shades of Night (2024 Feb 28)

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APOD Robot
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APOD: Shades of Night (2024 Feb 28)

Post by APOD Robot » Wed Feb 28, 2024 5:06 am

Image Shades of Night

Explanation: How does the sky turn dark at night? In stages, and with different characteristic colors rising from the horizon. The featured image shows, left to right, increasingly late twilight times after sunset in 20 different vertical bands. The picture was taken last month in Syracuse, Sicily, Italy, in the direction opposite the Sun. On the far left is the pre-sunset upper sky. Toward the right, prominent bands include the Belt of Venus, the Blue Band, the Horizon Band, and the Red Band. As the dark shadow of the Earth rises, the colors in these bands are caused by direct sunlight reflecting from air and aerosols in the Earth's atmosphere, multiple reflections sometimes involving a reddened sunset, and refraction. In practice, these bands can be diffuse and hard to discern, and their colors can depend on colors near the setting Sun. Finally, the Sun completely sets and the sky becomes dark. Don't despair -- the whole thing will happen in reverse when the Sun rises again in the morning.

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Ann
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Re: APOD: Shades of Night (2024 Feb 28)

Post by Ann » Wed Feb 28, 2024 5:49 am


Stunningly lovely colors! A nitpick here, though. What's the difference between the horizon band and the red band? In Dario Giannobile's other picture, the one you are taken to if you click the link Horizon Band, there is no red band. But the horizon band looks reddish.

Is there a difference between the horizon band and the red band? What is the 2°Earth shadow? And why is the horizon band (or the red band) reddish but the shadow of the Earth all blue? Inquiring minds want to know!

Ann
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Dario Giannobile
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Re: APOD: Shades of Night (2024 Feb 28)

Post by Dario Giannobile » Wed Feb 28, 2024 8:40 am

Dear Ann, thank you for you questions and for having posted my other image.
At that time i did not know anything about the red band and the second earth shadow. I just wrote horizon band in a place which was not perfectly correct. The horizin band should be pale blue or close to neutral.

After a deep search i read the book "light and color in the outdoor" by Marcel Minneart pag 285-297 where i discovered the red band and second earthshadow.

I also contacted some experts but as far as I know the science behind these two last bands is still unknow.
I hope that this image can contribute to an interesting discussion.

Let me add some details about this image:
1) 20 images Canon 6d, 50mm, f/5.6, iso 100;
2) AV priority modo to keep the same exposure;
3) Location: Plemmirio Reserve - Syracuse - Sicily;
4) Bibliography: "Light and colors in the outdoor", Marcel Minnaert pag.295-297;
5) same white balance.

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Re: APOD: Shades of Night (2024 Feb 28)

Post by johnnydeep » Wed Feb 28, 2024 11:51 pm

Ann wrote:Is there a difference between the horizon band and the red band? What is the 2°Earth shadow? And why is the horizon band (or the red band) reddish but the shadow of the Earth all blue? Inquiring minds want to know!
Where is the 2° Earth shadow mentioned? Perhaps I missed it...
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

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Ann
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Re: APOD: Shades of Night (2024 Feb 28)

Post by Ann » Thu Feb 29, 2024 4:47 am

johnnydeep wrote: Wed Feb 28, 2024 11:51 pm
Ann wrote:Is there a difference between the horizon band and the red band? What is the 2°Earth shadow? And why is the horizon band (or the red band) reddish but the shadow of the Earth all blue? Inquiring minds want to know!
Where is the 2° Earth shadow mentioned? Perhaps I missed it...
It's in the picture.


Ann
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johnnydeep
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Re: APOD: Shades of Night (2024 Feb 28)

Post by johnnydeep » Thu Feb 29, 2024 5:52 pm

Ann wrote: Thu Feb 29, 2024 4:47 am
johnnydeep wrote: Wed Feb 28, 2024 11:51 pm
Ann wrote:Is there a difference between the horizon band and the red band? What is the 2°Earth shadow? And why is the horizon band (or the red band) reddish but the shadow of the Earth all blue? Inquiring minds want to know!
Where is the 2° Earth shadow mentioned? Perhaps I missed it...
It's in the picture.


Ann
Thanks - I really need need glasses. Now, repeating your original question, what is it? And what is that little annotation line pointing to?
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}