APOD: Distorted Green Flash Sunset over Italy (2015 Sep 08)

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APOD Robot
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APOD: Distorted Green Flash Sunset over Italy (2015 Sep 08)

Post by APOD Robot » Tue Sep 08, 2015 4:11 am

Image Distorted Green Flash Sunset over Italy

Explanation: This was one strange sunset. For one thing, the typically round Sun appeared distorted, geometrically, and multiply layered. For another, some of these layers appeared unusually green. The Sun, of course, was just fine -- its odd appearance was caused entirely by its light refracting in the Earth's atmosphere. When layers of the Earth's atmosphere are unusually warm, layers of the Sun may appear distorted or even seen multiple times. The effect is most strong nearest sunrise and sunset when terrestrial inversion layers occupy distinct altitudes above the horizon. Different colors of the Sun may also become deflected by significantly different amounts, so that the uppermost superior image may appear momentarily green -- a phenomenon known as a green flash. The featured image was taken in February from Porto Venere, Italy, with San Pietro church situated in the foreground.

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Re: APOD: Distorted Green Flash Sunset over Italy (2015 Sep

Post by neufer » Tue Sep 08, 2015 1:50 pm

http://www.jameco.com/Jameco/workshop/puzzler/electronics-puzzler-ozone-solution.html wrote: How did Ozzie Measure Ozone in the Air Outside His Office?
By Forrest M. Mims III

<<As Ozzie watched the traffic light cycle though its colors of green, yellow and red, his boss's [challenge to measure ozone in the air outside his office window] kept cycling through his mind. Suddenly he shouted, "Yes!" and immediately searched online for more information about the absorption of visible light by ozone.

Ozzie soon learned that James Chappuis had long ago discovered the ozone absorption feature named for him. The Chappuis ozone absorption band extends from the blue to the red region of the visual spectrum with twin peaks in the yellow at around 575 nm and the orange at around 603 nm, as shown in this chart:

This chart is a simplified version of measurements of the Chappuis band by many separate teams. References to all of them listed at here

Ozzie learned that the absorption by ozone in the visible spectrum is much less than in the UV, but with care, it is definitely measurable. He compared this new information with the colors emitted by the traffic light and found that the yellow light was closest to the peak absorption of the Chappuis band. Ozzie then designed a simple photometer that used a silicon solar cell as a photodiode...>>
  • Full disclosure:
    Former Scientific American The Amateur Scientist Forrest M. Mims III is an old & dear friend of mine. :ssmile:
Art Neuendorffer

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Re: APOD: Distorted Green Flash Sunset over Italy (2015 Sep

Post by Ron-Astro Pharmacist » Tue Sep 08, 2015 5:14 pm

neufer wrote:
http://www.jameco.com/Jameco/workshop/puzzler/electronics-puzzler-ozone-solution.html wrote: How did Ozzie Measure Ozone in the Air Outside His Office?
By Forrest M. Mims III

<<As Ozzie watched the traffic light cycle though its colors of green, yellow and red, his boss's [challenge to measure ozone in the air outside his office window] kept cycling through his mind. Suddenly he shouted, "Yes!" and immediately searched online for more information about the absorption of visible light by ozone.

Ozzie soon learned that James Chappuis had long ago discovered the ozone absorption feature named for him. The Chappuis ozone absorption band extends from the blue to the red region of the visual spectrum with twin peaks in the yellow at around 575 nm and the orange at around 603 nm, as shown in this chart:

This chart is a simplified version of measurements of the Chappuis band by many separate teams. References to all of them listed at here

Ozzie learned that the absorption by ozone in the visible spectrum is much less than in the UV, but with care, it is definitely measurable. He compared this new information with the colors emitted by the traffic light and found that the yellow light was closest to the peak absorption of the Chappuis band. Ozzie then designed a simple photometer that used a silicon solar cell as a photodiode...>>
  • Full disclosure:
    Former Scientific American The Amateur Scientist Forrest M. Mims III is an old & dear friend of mine. :ssmile:

As a long time reader of Scientific American it was amusing to read a little back history to the magazine. Over the years the contents of that magazine has changed dramatically. When I began reading most of the content of the magazine was way over my head but the content really looked like something I thought I should attempt to understand. This month's Special Issue on Einstein is a lot more "digestible" but I'm not sure if that's due to me knowing more or the magazine being more directed at amateur scientists? I'm sure it's somewhere in the middle of the spectrum. :ssmile:

Thanks Art for your brief history lesson and filling a "gap" in my knowledge.
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Re: APOD: Distorted Green Flash Sunset over Italy (2015 Sep

Post by Boomer12k » Wed Sep 09, 2015 12:17 am

Wonderful picture of this phenomenon...

A LARGE Mirage Effect...

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