APOD: Nacreous Clouds over Sweden (2020 Jan 10)

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APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by APOD Robot » Fri Jan 10, 2020 5:06 am

Image Nacreous Clouds over Sweden

Explanation: Vivid and lustrous, wafting iridescent waves of color filled this mountain and skyscape near Tanndalen, Sweden on January 3. Known as nacreous clouds or mother-of-pearl clouds, they are rare. This northern winter season they have been making unforgettable appearances at high latitudes, though. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers the clouds can diffract sunlight after sunset and before the dawn.

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Ann
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Re: APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by Ann » Fri Jan 10, 2020 6:25 am

Living in the southernmost part of Sweden where the sky has been pretty much overcast since October, I have been envious of the Swedes from farther north (even Stockholm) who have been ooh-ing and and ahh-ing over the stunning nacreous clouds in their skies.

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Re: APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by Boomer12k » Fri Jan 10, 2020 9:02 am

Awesome...never heard of it before... looks like the sky's on fire...

Beautiful...

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Post by neufer » Fri Jan 10, 2020 12:37 pm

https://en.wikipedia.org/wiki/Polar_stratospheric_cloud wrote:
<<Polar stratospheric clouds (PSCs) are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m. They are best observed during civil twilight, when the Sun is between 1 and 6 degrees below the horizon, as well as in winter and in more northerly latitudes.

One main type of PSC is made up mostly of supercooled droplets of water and nitric acid and is implicated in the formation of ozone holes [when sunlit].

The other main type consists only of frozen ice crystals and is not considered harmful. This type of PSC is also referred to as nacreous (from nacre, or mother of pearl, due to its iridescence).
>>
Last edited by neufer on Fri Jan 10, 2020 4:15 pm, edited 1 time in total.
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Re: APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by orin stepanek » Fri Jan 10, 2020 12:49 pm

Today's picture would make a great background!
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Re: APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by DL MARTIN » Fri Jan 10, 2020 4:39 pm

Sadly at first glance, I thought it was a reflection of the Australian fires.

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Re: APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by MarkBour » Fri Jan 10, 2020 11:31 pm

I find this image incredibly beautiful.

Maybe I should just leave it at that, but it reminds me that I've become suspicious about a few things.
  1. I've never seen a comet with the naked eye. (I have seen one comet through a telescope once in my life. I definitely could not see it when I stepped away from the telescope.) Example APOD image: https://apod.nasa.gov/apod/ap170409.html
  2. I've never seen an aurora borealis, such as in: https://apod.nasa.gov/apod/ap190421.html
  3. I've never seen bioluminescent plankton in the ocean, e.g. https://apod.nasa.gov/apod/ap170418.html
  4. I've never seen nacreous clouds that looked like the ones in today's APOD.

    on the other hand:
  5. I have seen and photographed sundogs and such, and they are much like in the pictures (okay, https://apod.nasa.gov/apod/ap181221.html is exceptional, but the ones I've seen have been perhaps 50% as bright as that one.)
  6. I've never seen a Moondog (https://apod.nasa.gov/apod/ap130126.html),
  7. I've seen Lunar Halos of various types and they looked like the image: https://apod.nasa.gov/apod/ap160518.html
    I could go on ... crepuscular rays, anticrepuscular rays, rainbows ... these really are striking in person.
So, my limited experience with comets makes me think that, with only exceptions once in a very great while (e.g. 500 years), when I look for a comet in the sky with just binoculars or something small, it's going to be far fainter than the images captured with good light-gathering equipment. With the naked eye, in most cases, it will be a waste of effort. And it makes me guess that items b-d above are also generally super-enhanced in all the beautiful images.

I would be happy to travel and wait to see items (b)-(d) above. Definitely plan to go aurora-hunting some time. But will I be disappointed by the actual in those 3 cases ?
Mark Goldfain

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Re: APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by Chris Peterson » Sat Jan 11, 2020 2:15 pm

MarkBour wrote:
Fri Jan 10, 2020 11:31 pm
I find this image incredibly beautiful.

Maybe I should just leave it at that, but it reminds me that I've become suspicious about a few things.
  1. I've never seen a comet with the naked eye. (I have seen one comet through a telescope once in my life. I definitely could not see it when I stepped away from the telescope.) Example APOD image: https://apod.nasa.gov/apod/ap170409.html
  2. I've never seen an aurora borealis, such as in: https://apod.nasa.gov/apod/ap190421.html
  3. I've never seen bioluminescent plankton in the ocean, e.g. https://apod.nasa.gov/apod/ap170418.html
  4. I've never seen nacreous clouds that looked like the ones in today's APOD.

    on the other hand:
  5. I have seen and photographed sundogs and such, and they are much like in the pictures (okay, https://apod.nasa.gov/apod/ap181221.html is exceptional, but the ones I've seen have been perhaps 50% as bright as that one.)
  6. I've never seen a Moondog (https://apod.nasa.gov/apod/ap130126.html),
  7. I've seen Lunar Halos of various types and they looked like the image: https://apod.nasa.gov/apod/ap160518.html
    I could go on ... crepuscular rays, anticrepuscular rays, rainbows ... these really are striking in person.
So, my limited experience with comets makes me think that, with only exceptions once in a very great while (e.g. 500 years), when I look for a comet in the sky with just binoculars or something small, it's going to be far fainter than the images captured with good light-gathering equipment. With the naked eye, in most cases, it will be a waste of effort. And it makes me guess that items b-d above are also generally super-enhanced in all the beautiful images.

I would be happy to travel and wait to see items (b)-(d) above. Definitely plan to go aurora-hunting some time. But will I be disappointed by the actual in those 3 cases ?
Comets, either naked eye or through an eyepiece, never come close to what we see in images. They're simply too dim. I've seen maybe ten naked eye comets, and only two were bright enough to show color- Hale-Bopp and Hyakutake. And indeed, both were very impressive... but not so visually striking as images show. All the same, there's something very cool about seeing a comet. It isn't always about seeing intense color.

Auroras never look visually as intense as most of the images published (like the one you reference). But they are certainly bright enough to show lots of color, and the images don't capture their motion, which can produce a remarkable effect. So while they might appear visually somewhat dimmer and somewhat less saturated than images usually show, they are not to be missed if you have the opportunity.

The situation is similar for bioluminescent plankton. It's quite magical looking down off the side of a boat or pier and seeing blue streaks a few feet down from fish swimming, or to see waves breaking in pale blue light on the shore.

While I've never seen a display of nacreous clouds as impressive as what today's APOD shows, I have seen them, and today's image accurately captures the visual appearance (not surprising as images and our eyes are typically similar in bright light). If you have a chance to see such clouds, expect the apparent color to be very similar to what you see in pictures.

What about a total solar eclipse? That's one thing that images have only recently been made that come close to the visual experience... but never to the emotional experience.
Chris

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Re: APOD: Nacreous Clouds over Sweden (2020 Jan 10)

Post by MarkBour » Sun Jan 12, 2020 10:42 am

Thanks for the helpful (and encouraging) answers, Chris!

Then you had:
Chris Peterson wrote:
Sat Jan 11, 2020 2:15 pm
...
What about a total solar eclipse? That's one thing that images have only recently been made that come close to the visual experience... but never to the emotional experience.
I thought about including an eclipse in my little list, but felt like it was really different than the other examples.
I definitely like your assessment of it. It is an astronomical event that is so impressive in person that photos cannot do it justice.
Mark Goldfain