Bishops' Ring after Pinatubo eruption

After the 1991 Philippinian Pinatubo eruption, a large diffraction corona around the sun became visible worldwide. It was seen for many months in 1992 and 1993. This corona phenomenon is known as a "Bishops' Ring". It appears when sunlight shines through stratosperic layers of volcanic dust. The pattern of light and color is the same as that of the common corona in cloud droplets, consisting of a blueish white aureole directly around the sun, surrounded by a reddish to brownish diffuse and broad ring. The radius, however, is large and comparable to that of the common halo, being typically about 25 degs. This photograph was taken by Peter-Paul Hattinga Verschure, this one with super wide-angle lens and his second with a 20mm, from Deventer in The Netherlands on 29th March 1992. It was a spring day with very transparant air conditions, the best circumstances to see this phenomenon.

Shadows during the annular eclipse

Günther Können took these pictures in Madrid during the annular eclipse of 3rd Oct 2005. They are solar images projected onto three mutually perpendicular surfaces: one horizontal and two vertical. During the annular phase (right hand image) the solar images were ellipses, with their long axes oriented in different directions on the two walls and the steps and ground. This was not unexpected. However, in the picture showing the pre-annular phase, one notices that the sun crescents on the ground and steps comprised the more pointed part of the ellipse, whereas on the walls they are the more rounded part of the ellipse. The key is in the third picture, where the shadow of the roof overhang kinks from one projecting plane to the other. In hindsight, all of this is understandable, but I have never seen a comment on this 'solar image puzzle'.

Shadow Trident in Clouds

On April 15, I had the chance to observe a shadow trident above the pylon of our wind gauge on Wendelstein mountain (1835 m). When an observer is situated in the shadow of the pylon itself, there are regions above the pylon from where no light reaches the observer`s eye. If there is a “screen” of water droplets (clouds) or ice crystals (diamond dust) above the pylon, these regions can become visible as shadow rays. In my observation, cumulus clouds repeatedly passed rapidly over the top of the mountain and the shadow rays were briefly visible several times.

Birch pollen corona

A couple of days ago birch started flowering in Southern Finland and pollen coronae appeared in the sky. I photographed this corona yesterday and here is a composite of six individual images taken in one F-stop intervals and merged together with the HDRI-technique. The photo was enhanced rather heavily by applying unsharp mask and hue adjustment.

More natural version of the same photo is here. Another HDR-image of birch pollen corona, taken by Timo Kuhmonen, is here. See also the pollen corona around the moon by Jari Luomanen.

Twilight Colours during the total Sun Eclipse

A total Sun eclipse occured on 29th March 2006. The weather was very good in all southern Turkey. The sequence photo was taken by Jukka Ruoskanen on a beach close to the town called Side in Turkey. Few minutes before totality high clouds came, and a halo was seen. The halo, of course, vanished with the sunlight and reappeared again after the total phase - the high clouds responsible for the halo can be seen in some of the photos. The sky colours were truly amazing with deep bluish hue towards the zenith and a great "sunset-like" appearence all over the horizon. The other noteworthy points were a significant temperature drop and the peculiar light some minutes before second contact. At that time the shadows were really sharp too.

The second (16 mm) wide-angle picture of the sky during the totality of the 2006 eclipse is taken by Günther Können in Colakli near Side at the south coast of Turkey, straight on the central line. The horizontal field of view is 135 degrees. At the 4 o'clock position fron the overexposed corona, Venus is visible. The limiting magnitude during totality is +3, about the same as during twiligt with the sun 7 degrees below horizon. The light of the sky occurs because of leaking of light via the horizon, from regions where the sun is not completely eclipsed.

St. Elmo's fire on Airplane

This bright St. Elmo's fire was photographed by Martin Popek from Czech Republic on 24.03.2006 during a flight to Antalya, Turkey.

St. Elmo's fire is a spark discharge seen typically from soaring buildings. It is generated by a high voltage between the ground and the air.

Condensation Trail Iridescence

Jurgen de Boer (site) imaged this aircraft and contrail near to sunset on 2nd May. The aircraft was 10-20° from the sun. The structured iridescence is interesting. Seven or more colour bands are visible. The water droplets or ice crystals of the condensation trail will have had similar formation histories. Perhaps this produced rather uniform sizes and mean size variation along the trail thus accounting for the uniform colour bands?

Reflection Rainbow at the Dutch isle Terschelling

It is not the brightness of this reflection rainbow that it makes special, but rather it is the almost complete absence of a normal rainbow: of the latter, only the base is visible. Just before this picture was taken, the photographer Günther Können saw both the reflection bow and the normal rainbow. By the time he got his camera ready the normal rainbow had gone. A cloud had blocked the direct sunlight to the rainshower. Reflected sunlight was still illuminating raindrops via a path under the cloud. The reflecting surface was a small lake about 200 m across and 1100 m from the photographer. The picture was taken on 18 Nov 2005 at the Dutch isle Terschelling, 16:05 CET. Solar elevation: 3 deg.

Cloud droplet phenomena

This image shows how light scattering by small cloud droplets produces multiple effects that are actually all part of the same phenomena. The scene was taken by Leigh Hilbert in Washington State in January ’06. The shadow of the descending aircraft is surrounded by a bright glory (1, 2,) centred just behind the wing where Leigh was seated. Much further from the aircraft shadow is a circular cloud bow (1,2), a form of fogbow (1, 2), produced also by scattering by cloud water droplets. The classical light paths producing it are those of the rainbow (1,2,3) but diffraction by the small droplets produces something much broader and almost lacking in colour. Inside the main cloudbow is a supernumerary arc that, characteristically for cloudbows and fogbows, has more colour saturation than the primary. The more distant clouds at the image top have produced a narrower cloudbow indicating that their droplets were larger.

Bright Fogbow with serveral supernumerary arcs

On October 3, 2005, on the Wendelstein mountain (1834 m) a very bright fogbow with several supernumerary arcs appeared during the partial solar eclipse. In the centre of the fogbow there also appeared the spectre of the Brocken in variable intensity and size, according to the distance to the clouds. The spectre was also surrounded by a bright glory. Using a polarization filter, Carolin Baumann made this impressive photograph.