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| Greenland Ice Sheet Halos ~
Pictured on October 14, '12 at Summit Station by Ed Stockard (photos) with ice crystal images by Patrick Wright. Images ©Ed Stockard & Patrick Wright. |
"We used a camera mounted onto a microscope, exactly as described in snowcrystals.com .
I simply held glass slides up as perpendicular to the wind as I could, and the diamond dust would hit the slide and stick....there may be minor melting from heat conducting from my fingers through the slide (slightly rounded edges on some crystals). I had my pockets loaded with hand warmers and would rotate from one hand to the other, holding the slide up in the air as long as I could handle it. I must credit our other science tech Jennie Mowatt - I was trying all these fancy wood blocks and aluminum tubes to try and create a leeward effect to capture the crystals, and she walked up and said "why don't you just hold the slide up in the air against the wind?" |
| A mixture of plate, horizontal columns, Parry oriented columns and 'randomly' oriented diamond dust crystals generated the display. The plates, as usual, were not the regular hexagon idealisations so often drawn. Many even tended towards a triangular habit, ideal for producing bright 120° parhelia and even the ultra-rare Kern arc. The columns were much smaller and perhaps short enough to have produced the 22° and 46° rather than cluster crystals. The all-sky image at right has been brutally enhanced to show up the helic arc, Parry supralaterals and the overlapping 46° halo and supralateral arc. Apologies to Ed for marring his beautiful photography! |
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| "Today was the first day in quite some time that we have had significant sky optics. A remarkable part to the episode is that I was able to get these photos while Patrick was able to get some great shots of the actual diamond dust [crystals]. Shooting conditions were actually quite poor. Wind and diamond dust was blowing right toward the camera. My eyelashes were freezing together and my glasses fogged up quickly. Temps were -27C and winds 14-15knots straight on. Despite a balaclava and heavy pile hat and neck gaiter, my cheeks and forehead continually felt like they were frost nipped. The sun blocker would touch my cheek as well and I finally removed that. I tried to take surface halo photos as Marko [Riikonen] had taught me.... take a pic and side step and repeat, repeat, repeat. There was a crust on the snow and I would break through on each step probably about 15cm or more and I couldn't maintain a good flow and hold my breath for a photo. I gave up with that pretty quickly. Patrick said he took about a hundred diamond dust photos and gave up when his hands couldn't stand it anymore." |
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