Complex Halo January 21st 2017

On January 21st, after a long stretch of not getting any significant halos and not too long after observers in Hungary got a spectacular display, I observed a nice display here in the USA. The highlights of this one were the nice upper tangent arc and the 46 supralateral arc. I also got 120° parhelion too.

Diamond dust halos on the night of 12/13 January, part II

More photos from the 12/13 January night. The image above is a view opposite to the spotlight. Seen is blue circle, diffuse, Wegener and subhelic arcs. Below are two more images, the blue-minus-red image shows the “column 351/361”, which is the Kern arc equivalent of 46° supralateral arc. The lamp is about 5 degrees below the camera.

Marko Riikonen

More photos from three weeks ago in Rovaniemi

It seems putting the photos of the recent displays to my web page will delay. So, in a meanwhile here are two more photos of the display three weeks back.

When light source is at 0° elevation, some difficulties arises in identifying certain halos. Tricker arc and subanthelic arc merge together, as do helic and subhelic arcs. However, the subanthelic arc is formed by Parry-oriented crystals, while Tricker arc is from singly oriented columns. Because in this display the 46° supralateral arc is rather strong, and there are only weak indications of 46° Parry or Tape arcs, probably singly oriented columns were in command. The even brightness of the Tricker/subanthelic loop is also typical for Tricker arc. Subanthelic arc has strong brightenings on the sides - at least in the simulations - and that is actually what seems to be present in the the display of last weekend.

The reason why halos are seen so strongly in the halogen light is probably the relatively dark background sky as compared to sun or moon situation. Yet all the halogen lamp displays that I have photographed so far have been hampered by city lights. Once the crystal cloud drifts to the dark outskirts of the city, more intense appearances should be expected.

By Marko Riikonen

Complex display with odd radius column arcs in Finland

A long-lasting halo display was seen in Southern Finland on 25th April. The gems of the display were odd radius column arcs, of which 9, 20 and 24 degree arcs were seen. Additionally, 9 and 24 degree lower plate arcs as well as an 18 degree halo and possibly a 23 degree upper plate arc were visible for a short period of time during the day. The duration of the display was spectacular; for instance the Wegener anthelic arcs and 120° parhelia were continuously on the sky for almost three to four hours. At the latter stages of the display a beautiful 46° supralateral arc and magnificent circumzenith arc appeared. The display was photographed by many people - Marko Riikonen in Helsinki, Jari Luomanen in Tampere, Lauri Kangas in Espoo, Marja Wallin in Lahti, Timo Viinanen in Hameenlinna and Jukka Ruoskanen in Hyvinkaa.