An unknown halo and other displays by Jukka Ruoskanen
Jukka Ruoskanen has scanned his best halo slides ( 1 ). The material spans from year 1988 to 2005 and includes several displays of interest. Some cases are rather puzzling, like the one shown above, photographed on 23 December 2001. It contains strange pillars next to sun pillar. Explanation for these arcs is not known.