Thursday, November 15, 2007

More diamond dust in Rovaniemi

Last night diamond dust formed again in Rovaniemi with help of Ounasvaara ski resort snow guns. Two photos of what was seen in the light beam of a bright lamp are shown here.

In the upper image are diffuse anthelic arcs. In the lower image a number of common halos are seen together with Moilanen arc. Three white strikes extend from lamp to different directions to the left. Possibly these are parhelic circle (and parhelia), helic arc and superparhelia. Or, some of them may be artefacts formed by the lamp reflector.

Temperature was -6°C and it was overcast sky. The display was limited to the vicinity of the snow guns, these photos were taken at the top of the skiing flank. I was not able to get very far from the lamp, which accounts at least partly for the numerous separate crystals and diffuse looks of the halos. The lamp was on the elevated ground, but I did not make an estimate of the lamp angular elevation.

These are just two randomly chosen photos and may not represent the best output. Much more photos were taken, including crystal photos. I will return to these at some later time.

5 Comments:

Blogger Michael Ellestad said...

Nice catch there Marko! diffuse or partial those pics are nice. I like the diffuse arcs the best and I think I can see what appears to be tricker arc because I can see what appears to be part of a defined loop inside the diffuse arcs

17 November, 2007  
Blogger Marko Riikonen said...

I have stacking series so once I get to it, we will see if the anthelic region gets any better.

17 November, 2007  
Blogger Noli said...

I'm amazed that snow guns are able to produce so good cristals. Very nice display!

17 November, 2007  
Blogger Marko Riikonen said...

As I see it, snow guns don't produce the halo crystals. They produce ice nuclei for the crystal formation. When air is humid enough, a crystal starts to grow around the nuclei. On a dry day the cloud from the machines evaporates immediately - no halos.

19 November, 2007  
Blogger Noli said...

OK, thanks Marko, that seems to be much better explanation. :-)
By the way, someone some day might invent a new kind of snowgun especially for halo-lovers. I'll be waiting for that moment. :-)

19 November, 2007  

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