Pyramidal crystal halos

A funny coincidence that a halo-observer may want to experience is travelling to Egypt and seeing some pyramidal crystal halos.

This odd-radius display was photographed by Márk Laczkó of Budapest, Hungary somewhere over the southern borders of Romania. He was sitting on an airplane heading towards Egypt on 27th October. When he realised they were flying in cirrus clouds, he deliberately started looking for some halo phenomena. The surprisingly well distinguishable 18°, 20°, 23° and 24° halos were visible for about a minute at 06:21 UTC. Unfortunately, there is no documentation or report of a possible 35° halo. The original photo and two other pictures are also available (#1 and #2).

Odd radius halos in Czech Republic

On April 5th 2007 there was typical nice, but, dry“ cirrostratus in the sky without presence of halos. I was continuously checking the sky and after 10:00 I noticed very faint halo that had unusually wide upper part. That was very suspicious to me so I started to take photos which were after processed by Registax. You can see the result in the output picture. There are two separated halos which I later identified through the comparison with night sky, as 20° and 23° halos. Maybe there is also 35° halo, but it cant be certainly identified from the picture. The phenomenon could originate at 0,3-0,0-0,0 or 1,0-0,0-0,0 crystals.

I saw very similar displays with nice, "dry" cirrostratus and then with faint odd radius halos on June 22nd 2006 and August 26th 2006 so that is quite interesting.

Martin Popek

Odd radii in Southern Finland

A horrendously quiet April passed by without any noteworthy action (except Jarmo's fantastic bolide halo). Halo people were awakened from oblivion on 5th May, when a smooth cirrostratus veil crept in from west and offered plate crystals and odd radii halos. The display was seen and photographed by Ismo Luukkonen in Turku, Marko Riikonen in Helsinki (photo on the right by Marko) and Jukka Ruoskanen in Riihimäki.

Most likely all odd radius halos were on the sky, of which 9, 18, 20 and 35 degree halos were easily discernible. The 22-24 region may have consisted of all three possible rings. Also few of the odd radius plate arcs were present, although rather poorly.

Pyramidal heliac arc in Finland

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In 8 Feb 2007 an odd radius display was produced by local heating plant plumes in -28°C temperature in Vaala, northern Finland. I photographed this display on a road about 1.5 km away from the heating plant.

Odd radius halos in display were 18° halo, 23° upper plate arc, very faint 35° halo and rare pyramidal heliac arc. See arrows in a stacked and strongly unsharp masked photo shown.

Pyramidal heliac arc is formed by reflection from pyramidal side faces of horizontally oriented pyramidal ice crystal. It is usually visible near the sun only. It is usually very faint but this time I was able to see it also visually.

Same odd radius halos except 35° halo were also present in similar but much fainter display in Vaala couple of days earlier in 6 Feb 2007. More photos from both displays can be seen in Jarmo Moilanen's halo photo gallery or directly 8 Feb. 2007 here and 6. Feb 2007 here.

First odd radius halos observed 31st January 2007

While at work on break I saw some cirrus clouds gather in the sky and I later saw a halo appear so I got my camera out of the car and my sunglasses. As the minutes passed I notice that there were three halos: 9 degree halo 18 degree halo and possible 23 degree halo. The left side of the 9 degree halo looks strange because it is brighter on one side and has a somewhat vertical look to it.

When I later downloaded the pictures I went through them with adobe photoshop and I applied the USM and I noticed possible 20 degree halo and even a 35 degree halo! You can see at least 4 halos in the enhanced photo. The possible 9 degree column arc and 35 degree halo have been pointed out with black arrows.

Combination of high level cloud and diamond dust activity

On the evening of 30th January cirrostratus clouds filled the sky and odd radius halos (9, 20 and 35) were seen in the Moonlight in Hyvinkää, Finland. The 20 and 35 halos were very weak, and couldn't be seen with naked eye. In addition to the high clouds there were good but fast moving diamond dust areas on the ground level. At times the halo display was a combination of cirrostratus and diamond dust halos. In the photo on the left the parhelic circle was caused solely by diamond dust, whereas the other halos were mainly originated in high clouds. A collection of photographs taken by Jukka Ruoskanen is here. 9 degree halo was also seen in Espoo by Timo Kuhmonen, in Helsinki by Marko Riikonen, in Turku by Ismo Luukkonen and in Tampere by Jari Luomanen.

Exciting divergent light halos were photographed as well in Hyvinkää. A more detailed description of the divergent light halos is here.