Thursday, 19 January 2017

High-Cloud Tricker from Hungary

January 16 brought a whole-day high-cloud display to the greatest part of Hungary. The morning started with a spectacular sunpillar with bright upper-tangent arc, and the phenomenon became more and more complex during the day. Perhaps the most interesting feature of the display was caught by Ernő Berkó. He saw a Tricker-arc in Ludányhalászi, Hungary.

As he explained, he started reading emails from other Hungarian observers about the beautiful sunpillar of the morning, but in his region, there was thick fog with a night temperature of -17 °C. At 12:10 UT the fog disappeared, and he discovered the upper-tangent arc and the then symmetrical (about 60 degree-long) supralateral arc above it. Both were slightly coloured. While he was making preparations to take photos, the clouds thickened and covered the view. Later the conditions turned better again, the right side of the upper tangent arc strengthened, and he could take photos from 13:15 for 25 more minutes with the supra reaching lower and lower. He could see that it got brighter at the place where the parhelic circle crossed the upper tangent arc. It was only later that he realised the infralateral arc was also a bit visible and this caused the brightening. Ernő Berkó was trying to discover other halo forms but until 13:20 there were no other arcs, not even a 22 degree halo. It was only after this that the 22° halo started brightening here and there; the clouds were not uniform at all. A few minutes later he caught sight of the halos at the anthelic point. What he saw was mostly of the time a white oval brightening only, but the Tricker-arc also appeared, and sometimes a faint X-shape was also visible, suggesting Greenler arcs. To the naked eyes. the parhelic circle was invisible at this region of the sky. Later on the phenomenon weakened as the clouds thickened again. Ernő said he felt lucky that some days earlier he had shovelled a path in the snow to the back of his garden (where otherwise his telescope is), as this was the place where he could take images without many disturbing objects in view…and he caught the Tricker here, too.

It was Csaba Kozsa, who managed to take a picture of the infralateral arc. He was also reading messages in the buzzing Hungarian forum of halo observers, so in the early afternoon he rushed to his favourite observation point: Visegrád’s hill, Kis-Villám. This is the closest elevation to his home with a good view to South-Southwest, and the 270m hill made it possible to take a photo of the infra. He says that up till this day he had had very little knowledge about complex halo phenomena, but thanks to the several observations on Monday and the explanations of more experienced observers, he now knows where to look and what to pay more attention to.


  1. Made a simulation simulation for anthelic region. Based on this I don't quite see Tricker arc in the photo, at least not its characteristic fork higher up; rather I see anthelion of the diffuse arc and some diffuse arc V-shape. Anyway, Tricker or not, low sun anthelic arc stuff is always good catch in high clouds.

  2. Thanks for the simulation and the explanation, Marko!