Starship Asterisk*

Based on an email from an expert, the text of the main NASA APOD was changed to say that the 46 degree halo was also caused by refraction through ice crystals, not reflection from those crystals. I apologize for the oversight.

- RJN

[quote="bystander"][quote="RJN"]At 480 kilometers distance, an emailer pointed out that Vemdalen is not really very "near" Stockholm. [/quote]
In astronomical terms, it's very close. :mrgreen:[/quote]
Indeed. A mere 5 x 10[sup]-11[/sup] light years.

[quote="bystander"][quote="RJN"]At 480 kilometers distance, an emailer pointed out that Vemdalen is not really very "near" Stockholm. [/quote]
In astronomical terms, it's very close. :mrgreen:[/quote]
That is very funny bystander.

[quote="RJN"]At 480 kilometers distance, an emailer pointed out that Vemdalen is not really very "near" Stockholm. [/quote]
In astronomical terms, it's very close. :mrgreen:

[quote="Chris Peterson"][quote="BDanielMayfield"][quote="Chris Peterson"]
At the beginning of December in Vemdalen, the Sun never gets more than 5° above the horizon. It's basically always near sunrise or sunset (for the whole four hours the Sun is above the horizon at all).[/quote]
We now live just below 44 degrees North, but in the upper Snake River Plain near Henry's Fork of the Snake River. (Great place to see bald eagle, btw) Would it be more likely to see sun dogs up in the mountains, or does elevation matter (we're just below 5000 ft.)[/quote]
Elevation itself doesn't matter. But temperature does, and if you are at a higher elevation, you may have colder air near the ground (and often times, these ice crystals aren't very high).[/quote]
Good, as it is certainly cold enough here as it is in the single digits most nights and seldom gets above freezing now. We're learning to view the 30's as warm, like the locals.

At 480 kilometers distance, an emailer pointed out that Vemdalen is not really very "near" Stockholm. I therefore tweaked the NASA APOD's text to now say that the ski resort is in "central Sweden". We apologize for the oversight.

- RJN

[quote="BDanielMayfield"][quote="Chris Peterson"][quote="APOD Robot"]An observer may find themselves in the same plane as many of the falling ice crystals near sunrise or sunset.[/quote]
At the beginning of December in Vemdalen, the Sun never gets more than 5° above the horizon. It's basically always near sunrise or sunset (for the whole four hours the Sun is above the horizon at all).[/quote]
We now live just below 44 degrees North, but in the upper Snake River Plain near Henry's Fork of the Snake River. (Great place to see bald eagle, btw) Would it be more likely to see sun dogs up in the mountains, or does elevation matter (we're just below 5000 ft.)[/quote]
Elevation itself doesn't matter. But temperature does, and if you are at a higher elevation, you may have colder air near the ground (and often times, these ice crystals aren't very high).

[quote="Chris Peterson"][quote="APOD Robot"]An observer may find themselves in the same plane as many of the falling ice crystals near sunrise or sunset.[/quote]
At the beginning of December in Vemdalen, the Sun never gets more than 5° above the horizon. It's basically always near sunrise or sunset (for the whole four hours the Sun is above the horizon at all).[/quote]
We now live just below 44 degrees North, but in the upper Snake River Plain near Henry's Fork of the Snake River. (Great place to see bald eagle, btw) Would it be more likely to see sun dogs up in the mountains, or does elevation matter (we're just below 5000 ft.)

Bruce

[quote="APOD Robot"]An observer may find themselves in the same plane as many of the falling ice crystals near sunrise or sunset.[/quote]
At the beginning of December in Vemdalen, the Sun never gets more than 5° above the horizon. It's basically always near sunrise or sunset (for the whole four hours the Sun is above the horizon at all).

Oooohhh! I'm off to Aspen in February!

WOW, that was a spectacular one!!!!

Happy New Year, Everyone!!
:---[===] *

And a Happy New 2018 Year to this comunity and many Halos to come

[url=https://apod.nasa.gov/apod/ap180101.html][img]https://apod.nasa.gov/apod/calendar/S_180101.jpg[/img] [size=150]Sun Halo over Sweden[/size][/url]

[b] Explanation: [/b] What's happened to the Sun? Sometimes it looks like the Sun is being viewed through a giant [url=https://en.wikipedia.org/wiki/Lens_(optics)]lens[/url]. In the featured video, however, there are actually millions of tiny lenses: [url=http://www.its.caltech.edu/~atomic/snowcrystals/halos/halos.htm]ice crystals[/url]. Water may freeze in the [url=https://www.nasa.gov/sites/default/files/images/463940main_atmosphere-layers2_full.jpg]atmosphere[/url] into small, flat, six-sided, ice crystals. As these [url=http://en.wikipedia.org/wiki/Ice_crystal]crystals[/url] flutter to the ground, much time is spent with their [url=https://www.atoptics.co.uk/halo/orplate.htm]faces flat and parallel[/url] to the ground. An [url=http://littlefun.org/uploads/52410bb8e691b267f97d9278_736.jpg]observer[/url] may find themselves in the same plane as many of the falling ice crystals near sunrise or sunset. During this alignment, each crystal can act like a miniature lens, refracting sunlight into our [url=https://apod.nasa.gov/apod/ap100208.html]view[/url] and creating [url=http://www.atoptics.co.uk/halo/parhelia.htm]phenomena like parhelia[/url], the technical term for [url=https://apod.nasa.gov/apod/ap990823.html]sundogs[/url]. The [url=https://www.facebook.com/hakanhf/videos/10210053095156104/]featured video[/url] was taken a month ago on the side of a ski hill at the [url=https://www.skistar.com/en/Vemdalen/About-Vemdalen/]Vemdalen Ski Resort[/url] near [url=http://en.wikipedia.org/wiki/Stockholm]Stockholm[/url], [url=http://en.wikipedia.org/wiki/Sweden]Sweden[/url]. Visible in the center is the most direct image of the [url=https://solarsystem.nasa.gov/planets/sun]Sun[/url], while two bright [url=http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/sd.rxml]sundogs[/url] glow prominently from both the left and the right. [url=http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/halo.html]Also visible[/url] is the bright [url=http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/halo22.html]22 degree halo[/url] -- as well as the rarer and much fainter [url=http://www.atoptics.co.uk/halo/46hal.htm]46 degree halo[/url] -- also created by [url=http://www.atoptics.co.uk/halo/circular.htm]sunlight reflecting[/url] off of atmospheric ice [url=https://apod.nasa.gov/apod/ap080618.html]crystals[/url].

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