20° column arc

This minor odd radius came with a surprise after stacking. Outside the 18° halo / plate arc there seems to be a faint, but rather well defined 20° column arc. As there is no sign of 9° stuff, crystals had no middle prism which is rather rare situation. The display was observed on August 9 in Kontiolahti.

Lars Gislén's streetlight halo simulator

The halo application simulates streetlight halos ( 1 ). It can handle plate and column crystals as well as Parry oriented crystals. It can generate stereo pictures both for viewing in a stereo viewer or directly with "crossed yes". The application can also generate a data file with the 3D location of the crystals involved in the display that can later be viewed in a separate 3D viewer.

There is a short PDF manual together with an explanation of how the halo is simulated. Finally you can download the (rather messy) Java source code.

Detailed (large recycle value) halos may take the order of one hour to simulate. With the least detailed (recycle = 1) setting it takes much shorter time.

There are two implementations of the halo applications, one for Macintosh OS X 10.4+ and one for Windows. A Windows machine may need to download the Java Runtime Environment (JRE) that is available free ( 2 )

Text: Lars Gislén

Coloured parhelic circle

On 14 July Patrik Trncak from the Czech Republic observed a display with a coloured parhelic circle ( 1 ). The spectral colours were visible opposite the sun. Besides the more usual halos, the display also showed possible Lowitz arcs ( 2 - 3 ).

Sub-anthelion

First Panu Lahtinen thought he had seen the 120 deg sub-parhelia, but
after consulting Jarmo Moilanen, who noticed the shadow of the airplane,
the halo was identified to be "only" a sub-anthelion with a short
sub-parhelic circle attached to it. No other halos were seen. ( 1 - 2 - 3 )

The halos were seen on a flight from Helsinki to Ivalo on July 21, 2009
at 17:40 local time, and they were visible only for approximately 10-15
seconds.

119 pages of streetlight halos

The days are shortening and winter is coming soon. What a better way to get pumped for the upcoming diamond dust season than reading Walt Tape's 119 page treatment on spatial halos. New effects like superparhelic circle await for their discoverers. About half of the contents is the old stuff that you may have read already, but Walt has made some changes, so it is not bad idea to go through those parts as well.

Click on the image to go Walt's page to download it.

A mid-summer multihalo in Finland

This display was observed on 1 July 2009 in Tampere, Finland. The most prominent features were the bright upper tangent arc (contributing to a partial circumscribed halo) and the parhelic circle. A faint Wegener arc can be seen rising above the upper tangent arc. The sun elevation was 46 degrees. More photos on Jari Luomanen's website (1).

Odd radius halos 30 June, Finland

Halos were observed throughout Southern Finland. Above Jukka Ruoskanen's photo, click to go his site. Photos by others:

• Jari Luomanen


• Mika Aho


• Marko Riikonen