Structures deviating from the clean hexagonal form of an ideal ice crystal are believed to have an adverse effect on the formation of halos. Here we present images of a display and the large plate crystals that made it.
We call these plates with inner structures decorated plates. In addition to these decorations, the large crystal size also adversely affects halos as they tend to orient poorly.
Parhelia and a pillar were constantly visible, while subparhelia only appeared occasionally ( 1 ) as better quality crystal drifted by. Since the lamp was placed below the horizon, we could not see whether the circumzenithal arc was present.
The display occurred in Tampere in the morning of 4 January. Marko Riikonen sampled the crystals ( 2 ) while Jari Luomanen photographed the display ( 3 ).
Text: Marko Riikonen & Jari Luomanen