by MarkBour » Thu May 03, 2018 3:39 pm
neufer wrote: ↑Wed May 02, 2018 7:39 pm
A 44° lunar halo is a
second order doubly scattered caustic requiring a thick layer of coherently oriented ice crystals.
https://www.atoptics.co.uk/halo/44pars.htm wrote:
<<The halos of interest in this [David Bainbridge] panorama are the coloured 'smudges' on each side of the sun and twice as far from it along the parhelic circle as the sundogs. At first sight they could simply be brighter fragments of the 46° halo but the enlarged lower view shows that they are not. They are closer to the sun.
They are the fabled 44° parhelia. They were previously photographed during the famous Saskatoon display of December 3, 1970 (during which a Kern arc was also reported but not photographed) and purely visual sightings were occasionally reported since.
The 44° parhelia are
rare examples of multiple scattering. In effect they are 'sundogs of sundogs' formed by rays that have already passed through a plate crystal - and would otherwise have formed a sundog - intercepting a second plate crystal and being further deflected. The double deflection has a minimum deviation angle of 44°. Very high plate crystal concentrations are needed. As an alternative explanation, peculiar geometries have been invoked to form the parhelia from only the single crystal scattering that normally produces halos.>>
Thanks, that's a pretty cool photo, 4 sun dogs! Perhaps the outer ones could be called sun dog dogs.
(If I ever see one, I'll probably say "hot-diggity dog":
https://www.youtube.com/watch?v=lHhheCf0G1I .)
Here are two other cases of multiple halos, and again, these introduce new halos and explanations I'd never heard of before. (I'm not sure how sure everyone is of these explanations, actually.)
A double lunar halo:
http://earthsky.org/todays-image/photo- ... e-9-degree
A clearer 9-degree halo around the Sun:
https://www.atoptics.co.uk/halo/pyredens.htm
So beware ... if you do too much ice, you'll begin to see all sorts of pretty lights.
[quote=neufer post_id=282057 time=1525289959 user_id=124483]
[quote=MarkBour post_id=282054 time=1525286457 user_id=141361]
I have seen one image of what I believe shows a second "solar 22 degree" halo. A 44-degree halo, if you will.
[url]https://en.wikipedia.org/wiki/Halo_(optical_phenomenon)#/media/File:Halo_phantom-sun.jpg[/url]
Well, actually, for some reason, this is listed as a 46-degree halo.
[url]https://en.wikipedia.org/wiki/46%C2%B0_halo[/url]
I have no idea why it is not 44. Further reading is needed!
Has anyone ever observed a double lunar halo? Perhaps there is not sufficient brightness for the naked eye.[/quote]
A 44° lunar halo is a [b][u][color=#FF0000]second[/color] order [color=#FF0000]doubly[/color] scattered[/u][/b] caustic requiring a thick layer of coherently oriented ice crystals.
[quote=" https://www.atoptics.co.uk/halo/44pars.htm"]
<<The halos of interest in this [David Bainbridge] panorama are the coloured 'smudges' on each side of the sun and twice as far from it along the parhelic circle as the sundogs. At first sight they could simply be brighter fragments of the 46° halo but the enlarged lower view shows that they are not. They are closer to the sun.
They are the fabled 44° parhelia. They were previously photographed during the famous Saskatoon display of December 3, 1970 (during which a Kern arc was also reported but not photographed) and purely visual sightings were occasionally reported since.
The 44° parhelia are [b][u]rare examples of [color=#FF0000]multiple scattering[/color][/u][/b]. In effect they are 'sundogs of sundogs' formed by rays that have already passed through a plate crystal - and would otherwise have formed a sundog - intercepting a second plate crystal and being further deflected. The double deflection has a minimum deviation angle of 44°. Very high plate crystal concentrations are needed. As an alternative explanation, peculiar geometries have been invoked to form the parhelia from only the single crystal scattering that normally produces halos.>>[/quote]
[/quote]
Thanks, that's a pretty cool photo, 4 sun dogs! Perhaps the outer ones could be called sun dog dogs.
(If I ever see one, I'll probably say "hot-diggity dog": [url]https://www.youtube.com/watch?v=lHhheCf0G1I[/url] .)
Here are two other cases of multiple halos, and again, these introduce new halos and explanations I'd never heard of before. (I'm not sure how sure everyone is of these explanations, actually.)
A double lunar halo: [url]http://earthsky.org/todays-image/photo-moon-halo-22-degree-9-degree[/url]
A clearer 9-degree halo around the Sun: [url]https://www.atoptics.co.uk/halo/pyredens.htm[/url]
So beware ... if you do too much ice, you'll begin to see all sorts of pretty lights.