Halos and Sundogs Natural Art, Miscellaneous

When there are ice particles in the air you may see halos and Sundogs (also spelled as two words "Sun Dogs"). Before we describe these let's go back a couple of steps. We've all seen rainbows - beautiful multicoloured arcs which we see when the sun shines on falling rain. As long as there is rain the rainbows are equally bright along their lengths. This is because light is being reflected by raindrops which are more or less round - and look about the same from all directions.

Sometimes you can see large circular halos around the moon on cold clear nights (and, if you are very lucky, around the sun close to sunrise or sunset on frosty days). These halos are refracted to you by ice particles which are rather random in their orientations, again giving unformly illuminated halos.

But snowflakes are not random. Well-formed ones are intricate hexagonal flake designs, which, in still air, tend to orientate themselves in the same manner. Because their orientation is no longer random they reflect and refract light in specific ways, creating extraordinary displays in the sky.

Upper Tangent Arc NA12	Most people never see halos or sundogs. This is mainly because they don't look for them. Sundogs and halos are not uncommon in northern European skies. To see them the sun must be fairly low in a clear and frosty sky, and you need to look about 22 degrees to the right and left of the sun (where there can be Sundogs - "false suns" or Parhelia), and about 22 degrees above the sun (where there could be the Upper Tangent Arc). There may also be a further display (Lower Tangent Arc or Pillar) 22 degrees below the sun, but this often falls below the horizon. You may need to sheild your eyes from the sun, which is far far brighter than its imitators, and you must NEVER look directly at the sun.
I'm not certain that this is the truth, but as a boy I was told that the name "Sundog" was coined by irritated sailors who discovered that they had been navigating by the wrong sun! It is possible for the real sun to be obscured by a low cloud leaving a Sundog or Parhelion confusingly visible. Sundogs, like the Upper Tangent Arc, have a faint rainbow element to to their appearance, but the main impression is of white brightness, leading to occasional confusions with reality, and presumably to superstitious fears in the past.	Sundog (right) or Parhelion NA10
Circumzenithal Arc NA17	The most beautiful halo is the Circumzenithal Arc which is an inverted rainbow-like halo about 45 degrees above the sun. You will usually need to look almost straight up to see it. It can be vividly coloured and has been engagingly described as a rainbow "Smiley" in the sky.
There are quite a number of less frequent and often more intricate skyworks which are seen from time to time. When we took these photos in the early afternoon of 2nd March 2007 in the pretty market town of Gisburn in Ribblesdale, North Lancs, we were lucky enough to see parts of the less common Supralateral Arc, which intersects the Tangential Arc.  In our photos you can see that details such as the Supralateral Arc come and go, and this is a feature of watching halos and sundogs. They are only visible while the right types of ice crystals exist in the right parts of the sky. We watched a changing display for about 30 minutes before it finally disappeared.	Circumzenithal and Supralateral Arcs NA15