Yvette (one of our regulars here) let me know about a photograph that she took of a sundog the other day. It appeared on the Spaceweather website (you’ll need to set the calendar there to June 14th to see it in context), and since there may be a few of you (like me) who wonder what a sundog (or sun dog) is, here it is:
Yvette also put it up on her blog (which is an interesting and nicely illustrated read, by the way) together with a picture of the broader view showing the nearby sun.
My confession today is that I had no idea that is what those optical phenomena were called! No, really. You’ll also find them called parhelia (the plural; singular “parhelion”)…. they are always near the sun, you see. (Less common are the images that form somewhat further away from the sun (a “paranthelion”), or quite a bit further away (an “anthelion”). These are not, as I understand, properly referred to as sundogs.). I always used to wonder about them (and their cousins, the halos you sometimes see around the sun) when I was a child, but never talked to anyone about them back then (I kept a lot of wondering to myself) and the urge to find out what they were called was never strong enough I suppose. I think I’d satisfied myself that they were caused by refraction in the atmosphere, but again, I’ll admit that I’d never really gone and verified this anywhere. (Same for the effects around the moon you can sometimes see.) So I never learned of the significance of 22o, which is the angle the light from the sun bends through when it passes through the hexagonal ice crystals floating in concert in the upper atmosphere. (The other, further away ones are formed at larger angles.) It was when Yvette said sundog that I went a-Googling (as one does) and found many links and found out some of this. You can easily find some too. I’ll point out the University of Illinois site (Department of Atmospheric Sciences) I found that had a nice simple illustration of the formation of sun dogs:
Here’s their text about the formation of the optical effect:
Sundogs, also known as mock suns or “parhelia”, are a pair of brightly colored spots, one on either side of the sun. Sundogs form as sunlight is refracted by hexagonal plate-like ice crystals with diameters larger than 30 micrometers and their flat faces horizontally oriented.
Sundogs are visible when the sun is near the horizon and on the same horizontal plane as the observer and the ice crystals. As sunlight passes through the ice crystals, it is bent by 22 degrees before reaching our eyes, much like what happens with 22 degree halos. This bending of light results in the formation of a sundog.
The difference between sundogs and halos is the preferential orientation of the ice crystals through which the light passes before reaching our eyes. If the hexagonal crystals are oriented with their flat faces horizontal, a sundog is observed. If the hexagonal crystals are randomly oriented, a halo is observed.
There’s the inevitable Wikipedia article here, where I found a link to an excellent article by Keith C. Heidorn, the “Weather Doctor”. You can learn about moondogs (a “paraselene”, with a further-away cousins called a “parantiselene” or “antiselene”, depending upon the angle…) from this site, for example. For lots more on haloes, sundogs and their cousins, including some marvellous photographs, see this site* and this site*.
-cvj
(Thanks Yvette Cendes, and *thanks Carl Brannen)
Something incredible happen to our town in Medan
A perfect rainbow ring around the sun appeared at noon on 22 Sep 2008, we believe also known as Sun Dogs
You might be interested to see the photos we took below:
http://www.medanku.com/rainbow-halo-sun/
Warmest Greetings from
MedanKu.com
Please check out this youtube SUNDOG video. Great Job!
Enjoy!
Schubert’s Winterreise, from the poems by Müller: the next-last song is called “Die Nebensonnen”, and starts, “Drei sonnen sah ich am Himmel steh’n”. I was infuriated when listening to WGBH radio some time back, when a stupid musician talking about the song-cycle referred to the sight as “phantasmagoric”. There’s nothing strange about them where I come from, on the East Coast, though of course most people never look up into the sky and therefore don’t notice them.
I always look for them in November and early December when I’m back home in the East; the best ones I’ve seen here in California appeared one evening in summer up at the Mount Wilson Observatory.
Love the graphic, thanks for including!
The only times I’ve seen COMPLETE (both sides of the circle) sun dogs is whilst flying.
Once at DPA airport it seemed like we took off through a sundog! (Wrote a poem on the experience, but can’t find it just now….).
Yes, third from the left at the top, in Carl Brannen’s halo website is what I saw.
Thanks Carl… I will.
And have a great trip!
-cvj
We get these big time up in the relatively Northern latitudes (Seattle). A good set of pictures is at the halo website, and you should link them in. Here’s a description of 19 sun halos to look for, with scientific names, and a list of all observed rare halos. Somewhere around the web, there’s a photograph of more than a dozen simultaneously appearing halos in Antartica, if I recall, but I can’t find it.
As far as photographing the Cascade mountains in late spring, I’ve found a willing companion, bought the stuff required (sun glasses for snow blindness, an emergency kit, rope, a couple emergency shelters) and found a place to cheaply rent mountaineering axes (REI) so we will leave in a few days when convenient. Hopefully I will not require helicopter rescue and will have photographs up in a week.
I saw this photo, but did not that it was one of the regulars at the blogs. Congrats on getting the image on SW, Yvette! Very nice shot. 🙂
Btw, one of the great sites (maybe THE best) on atmospheric optics is, well, Atmospheric Optics. The site owner, Les Cowley, is the resident expert at SW.
Excellent. I just love all these atmospheric effects. They are quite common when one takes the care to look. Often the sky is milky and forward scattering makes the sky very bright around the sun, masking these beautiful halos from most eyes.
My technique is, whenever the sky looks suitable, is to watch the shadow of my head disappear behind another shadow. It will then be safe to look up into the bright glare. A polarising glass will frequently enhance the effects 10-fold.
If I may be forgiven an anecdote… The most beautiful effect that I had the pleasure to witness was when gold panning in Australia. I had filled the pan with gravel and was swirling it around hopefully. My eyes suddenly re-focussed onto a flashing rainbow entirely contained and right in the middle of the pan! It was an upper contact arc, beautiful and bright, reflected from the water within the pan.
That’s the sort of thing that I love: sudden joins from far flung realms of thought. In this case a moment that lives with me after some 15 years.