APOD: An Airglow Fan from Lake to Sky (2019 Feb 03)

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APOD Robot
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APOD: An Airglow Fan from Lake to Sky (2019 Feb 03)

Post by APOD Robot » Sun Feb 03, 2019 5:06 am

Image An Airglow Fan from Lake to Sky

Explanation: Why would the sky look like a giant fan? Airglow. The featured intermittent green glow appeared to rise from a lake through the arch of our Milky Way Galaxy, as captured during 2015 next to Bryce Canyon in Utah, USA. The unusual pattern was created by atmospheric gravity waves, ripples of alternating air pressure that can grow with height as the air thins, in this case about 90 kilometers up. Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction. More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.

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JohnD
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Re: APOD: An Airglow Fan from Lake to Sky (2019 Feb 03)

Post by JohnD » Sun Feb 03, 2019 9:58 am

Wouldn't this view have looked more like this?
The arch of the Milky Way stretches a lot further around the horizon.

John
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Tszabeau

Re: APOD: An Airglow Fan from Lake to Sky (2019 Feb 03)

Post by Tszabeau » Sun Feb 03, 2019 12:39 pm

Everyone act normal... the cops just drove-up.

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Re: APOD: An Airglow Fan from Lake to Sky (2019 Feb 03)

Post by orin stepanek » Sun Feb 03, 2019 1:02 pm

JohnD wrote:
Sun Feb 03, 2019 9:58 am
Wouldn't this view have looked more like this?
The arch of the Milky Way stretches a lot further around the horizon.

John
Hi John!
It's amazing what a computer can do with photography! If I want a picture for a background; i usually have t size it first so as not to lose the aspect ratio! Is it common to stretch a picture one way or another to get a desired look? I wonder how many pictures are worked on to present a certain look? :wink:
Orin

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Re: APOD: An Airglow Fan from Lake to Sky (2019 Feb 03)

Post by E Fish » Sun Feb 03, 2019 2:29 pm

Is airglow ever really that dramatic? It seems like it would require a long exposure or at least some processing to have it show up so dramatically, especially with all the detail showing up with the Milky Way.

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Re: APOD: An Airglow Fan from Lake to Sky (2019 Feb 03)

Post by Chris Peterson » Sun Feb 03, 2019 2:32 pm

E Fish wrote:
Sun Feb 03, 2019 2:29 pm
Is airglow ever really that dramatic? It seems like it would require a long exposure or at least some processing to have it show up so dramatically, especially with all the detail showing up with the Milky Way.
Airglow, like the Milky Way, doesn't show color to the human eye. All images like this take advantage of the ability of a camera to show color and contrast that we cannot see with our eye alone. (Which is kind of the point!)
Chris

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neufer
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The silence of cones.

Post by neufer » Sun Feb 03, 2019 3:52 pm

Chris Peterson wrote:
Sun Feb 03, 2019 2:32 pm
E Fish wrote:
Sun Feb 03, 2019 2:29 pm

Is airglow ever really that dramatic? It seems like it would require a long exposure or at least some processing to have it show up so dramatically, especially with all the detail showing up with the Milky Way.
Airglow, like the Milky Way, doesn't show color to the human eye. All images like this take advantage of the ability of a camera to show color and contrast that we cannot see with our eye alone. (Which is kind of the point!)
https://www.atoptics.co.uk/highsky/airglow1.htm wrote:
<<To see [airglow one] needs long dark adaptation. Eventually, when stars are almost blinding and the Milky Way is a bright convolved mass, the sky itself will be seen to be luminous and a hand held towards the heavens will be a black silhouette.

It is strongly coloured yet it is without colour to our unaided eyes because its light is below their threshold of colour perception. From orbit it is a green bubble enclosing the world.

Look carefully and banded or uneven structure changing slowly over minutes might be visible. The bands can appear to cross the sky and converge towards two opposite points on the horizon in the same way that crepuscular and anticrepuscular rays do. The reason is the same, the glowing bands are parallel and perspective effects makes them appear to converge.>>
Art Neuendorffer

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Chris Peterson
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Re: The silence of cones.

Post by Chris Peterson » Sun Feb 03, 2019 3:56 pm

neufer wrote:
Sun Feb 03, 2019 3:52 pm
Chris Peterson wrote:
Sun Feb 03, 2019 2:32 pm
E Fish wrote:
Sun Feb 03, 2019 2:29 pm

Is airglow ever really that dramatic? It seems like it would require a long exposure or at least some processing to have it show up so dramatically, especially with all the detail showing up with the Milky Way.
Airglow, like the Milky Way, doesn't show color to the human eye. All images like this take advantage of the ability of a camera to show color and contrast that we cannot see with our eye alone. (Which is kind of the point!)
https://www.atoptics.co.uk/highsky/airglow1.htm wrote:
<<To see [airglow one] needs long dark adaptation. Eventually, when stars are almost blinding and the Milky Way is a bright convolved mass, the sky itself will be seen to be luminous and a hand held towards the heavens will be a black silhouette.

It is strongly coloured yet it is without colour to our unaided eyes because its light is below their threshold of colour perception. From orbit it is a green bubble enclosing the world.

Look carefully and banded or uneven structure changing slowly over minutes might be visible. The bands can appear to cross the sky and converge towards two opposite points on the horizon in the same way that crepuscular and anticrepuscular rays do. The reason is the same, the glowing bands are parallel and perspective effects makes them appear to converge.>>
Although, I have on occasion seen airglow that was bright enough that very little dark adaptation was required- just a minute outside. But even then, it's not bright enough to show any color.
Chris

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