Talk:22° halo

22 degrees
Could a knowledgeable person improve the caption of the diagram to explain the beam of light is being bent by 22 degrees? It took me a couple of readings to deduce why the phenomenon is called "22 degrees". Tempshill (talk) 06:56, 21 April 2009 (UTC)

Merger proposal
This is a procedural proposal on behalf of Punkdigerati, who left a comment at Talk:Moon ring stating that he believes that Moon ring duplicates 22° halo, but did not know the guidelines on merging. I personally believe that Moon ring could be merged into this article. Chris the Paleontologist (talk • contribs) 17:45, 4 February 2012 (UTC)
 * Silence is golden, no objections after a month, go for it, I beg of you. Rgrds. --64.85.220.22 (talk) 07:18, 8 March 2012 (UTC)
 * Months later and the proposal has not been closed. Since there appears to be no controversy I will close it and merge the pages, redirecting the term Moon Ring to the 22° halo article.

visible on as many as 100 days per year
The sentence "A 22° halo may be visible on as many as 100 days per year—much more frequently than rainbows" is very vague. Where is it visible 100 days a year? Some locations are almost always too cloudy while others are almost always completely clear. In some locations rainbows are visible all the time during day, such as next to waterfalls with clear skies, and I assume that some locations have rain formed rainbows more frequently than halos. 132.76.10.43 (talk) 15:52, 27 November 2015 (UTC)


 * Perhaps a link to this page is in order? http://www.atoptics.co.uk/halo/whyinfr.htm EDIT: Or this one? https://submoon.wordpress.com/2013/12/03/a-list-of-known-halos-and-some-frequency-numbers/ Drabkikker (talk) 13:27, 30 November 2015 (UTC)

lead photo represents different phenomenon with its own wiki page
The leading photo at the top of this article appears to represent the rarer 46° halo rather than the 22°. Propose moving it to the 46° article and replacing it here with a more relevant illustration. — Preceding unsigned comment added by Wchardy (talk • contribs) 16:42, 8 December 2017 (UTC)

Just call the parhelia sundogs
In the image gallery, the sun dogs are called parhelia, but I think people would better recognize "sun dogs." Even the sun dog page itself claims that they're formerly called parhelia. Either way, using parhelia's singular (parhelion) would be a better fit for the captions. --OneBlueGlove (talk) 22:26, 15 May 2019 (UTC)
 * Formally, not formerly. Drabkikker (talk) 10:47, 17 May 2019 (UTC)

New illustration diagram uploaded
At the Graphics Lab Illustration Workshop (recent diff), another editor requested creation of a 22° Halo graphic. I created the graphic shown at right, previously unaware of the existence of a 2011 graphic, File:22 degree halo Observer looking at 22 degree halo.svg, which is already used in this article. I didn't intend to supplant a longstanding image, but if you think the new graphic is preferable then feel free to insert it, or if it can be improved then please let me know. —RCraig09 (talk) 20:03, 13 July 2020 (UTC) P.S. I purposely omitted non-numeric text, so that it can be used internationally. —RCraig09 (talk) 20:46, 13 July 2020 (UTC) P.P.S. I wasn't sure if the halo has the full range of rainbow colors, or if they are only red and blue. Experts, please clarify.

Full moon, or any moon?
Does this only occur when the moon is full? If so, why? Ddnaylor (talk) 11:32, 28 January 2021 (UTC)

Other planets?
Can they occur on Mars? Grassynoel (talk) 11:05, 3 July 2021 (UTC)
 * According to [//www.atoptics.co.uk/halo/oworld.htm this website], halos should be possible on other planets that also have hexagonal water ice crystals in their atmosphere. I don't know of any other sources to corroborate this website's claims though. CoronalMassAffection (talk) 18:01, 22 November 2021 (UTC)

Where do the numbers 1.309 and 40.88° come from?
In the "Formation" section, notice the sentence: For $$n$$ = 1.309, the angle of minimum deviation is almost 22° (21.76°, when $$i$$ = 40.88°). Where does the refractive index 1.309 come from? Where does the angle of incidence 40.88° come from? Mksword (talk) 09:34, 18 March 2022 (UTC)
 * The refractive index $$n$$ = 1.309 is that of ice and the angle of incidence $$i$$ = 40.88° is the angle that results in a minimum deviation of $$\theta$$ = 21.76°. In other words, plugging these values for $$n$$ and $$i$$ into
 * $$\theta = i+\sin^{-1}\left[n\sin\left(\frac{\pi}{3}-\sin^{-1}\frac{\sin i}{n}\right)\right]-\frac{\pi}{3}$$
 * with the necessary conversions between degrees and radians gives $$\theta$$ = 21.76°.
 * [//www.desmos.com/calculator/7honwcaqqe This graph] might help. The vertical axis is the angle of incidence in degrees and the horizontal axis is the resulting deviation angle in degrees. Note at which incident angle gives the minimum deviation angle. I think the article needs to make this more clear. CoronalMassAffection (talk) 15:00, 18 March 2022 (UTC)
 * Thanks! Further questions:
 * The article goes on to say:

More specifically, the angle of minimum deviation is 21.84° on average ($$n$$ = 1.31); 21.54° for red light ($$n$$ = 1.306) and 22.37° for blue light ($$n$$ = 1.317).
 * So, that is saying that the refractive index $$n$$ = 1.306 for red light in ice, $$n$$ = 1.317 for blue light in ice, and $$n$$ = 1.31 for "average" light in ice. Is that correct?
 * By "average" light, we mean light whose wavelength is the average wavelength of visible sunlight. Is that correct?
 * Mksword (talk) 06:33, 19 March 2022 (UTC)
 * I do not know if it is correct as the original writer did not provide a source, though I do believe that is what they had meant. A cursory search online has not yielded any sources that could be added with matching results for the refractive indices so I will add a Template:CN for now. Additionally, the use of average is pretty ambiguous so I cannot confirm that what you wrote is what the original writer had meant. CoronalMassAffection (talk) 15:32, 21 March 2022 (UTC)