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APOD: Shades of Night (2024 Feb 28)
Posted: Wed Feb 28, 2024 5:06 am
by APOD Robot
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.
Re: APOD: Shades of Night (2024 Feb 28)
Posted: Wed Feb 28, 2024 5:49 am
by Ann
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
Re: APOD: Shades of Night (2024 Feb 28)
Posted: Wed Feb 28, 2024 8:40 am
by Dario Giannobile
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.
Re: APOD: Shades of Night (2024 Feb 28)
Posted: Wed Feb 28, 2024 11:51 pm
by johnnydeep
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...
Re: APOD: Shades of Night (2024 Feb 28)
Posted: Thu Feb 29, 2024 4:47 am
by Ann
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
Re: APOD: Shades of Night (2024 Feb 28)
Posted: Thu Feb 29, 2024 5:52 pm
by johnnydeep
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?