Comments and questions about the
APOD on the main view screen.
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APOD Robot
- Otto Posterman
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by APOD Robot » Fri Mar 11, 2022 5:05 am
When Rainbows Smile
Explanation: /24/]Want to see a rainbow smile? Look near the zenith (straight up) when the sun is low in the sky and you might. This example of an
ice halo known as a circumzenithal arc was captured above a palm tree top from Ragusa, Sicily on February 24. The vividly colorful arcs are often called smiling rainbows because of their upside down curvature and colors. For
circumzenithal arcs the
zenith is at the center and red is on the outside, compared to rainbows whose arcs
bend toward the horizon after a downpour. True rainbows are formed by water droplets refracting the sunlight to produce a spectrum of colors,
though. Circumzenithal arcs are the product of
refraction and reflection in flat hexagonal ice crystals, like the ice crystals that create sundogs, formed in high thin clouds.
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Chris Peterson
- Abominable Snowman
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by Chris Peterson » Fri Mar 11, 2022 5:38 am
Off my deck a few years ago, in context with some other common halos.
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De58te
- Commander
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by De58te » Fri Mar 11, 2022 9:41 am
Hmm. I wonder why smiling rainbows are usually described as curved arcs, rather than described as curved bow shaped? Rainarcs anyone?
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XgeoX
- Science Officer
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- AKA: Uncle Rico
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by XgeoX » Fri Mar 11, 2022 12:11 pm
Stunning pic Chris.
Thanks for sharing!
Eric
Ego vigilate
Ego audire
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orin stepanek
- Plutopian
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by orin stepanek » Fri Mar 11, 2022 1:05 pm
ArcoCircumzenitale_1024c.jpg
Today's APOD= A-OK!
I have seen circular rainbows from the spray of my garden hose!
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Orin
Smile today; tomorrow's another day!
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NCTom
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by NCTom » Fri Mar 11, 2022 4:05 pm
Beautiful picture, Chris. Out of curiosity, how long would the conditions last for those arcs to remain as they are? Seconds, minutes?
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Chris Peterson
- Abominable Snowman
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by Chris Peterson » Fri Mar 11, 2022 4:14 pm
NCTom wrote: ↑Fri Mar 11, 2022 4:05 pm
Beautiful picture, Chris. Out of curiosity, how long would the conditions last for those arcs to remain as they are? Seconds, minutes?
IIRC, the arcs that day were around for a good hour. They kind of come and go in intensity at the thin clouds pass through.
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Fred the Cat
- Theoretic Apothekitty
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- AKA: Ron
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by Fred the Cat » Fri Mar 11, 2022 4:24 pm
Quite the juxaposition; cold weather and a
palm tree!
But it makes
me smile.
Freddy's Felicity "Only ascertain as a cat box survivor"
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MarkBour
- Subtle Signal
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by MarkBour » Fri Mar 11, 2022 4:46 pm
Wow, I've never seen one of these before. The "refraction and reflection" linked article says "The circumzenithal arc, or 'smile in the sky' is fairly common but is rarely seen." I wonder if there is any weather data that could help one to know when such a wonder is more likely to appear.
Mark Goldfain
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Chris Peterson
- Abominable Snowman
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by Chris Peterson » Fri Mar 11, 2022 4:59 pm
MarkBour wrote: ↑Fri Mar 11, 2022 4:46 pm
Wow, I've never seen one of these before. The "refraction and reflection" linked article says "The circumzenithal arc, or 'smile in the sky' is fairly common but is rarely seen." I wonder if there is any weather data that could help one to know when such a wonder is more likely to appear.
I see them all the time. All you need is those thin ice clouds, which are common enough in most places in the winter. The reason they are rarely seen is probably the same reason so many common astronomical things are rarely seen: most people just don't look up very much. If you can see sundogs or the usual halo around the Sun, there's a good chance there's also a circumzenithal arc high in the sky above it.