Sunday, 31 January 2021

Double CZA spotted in Czechia


At the 19th of January 2021, Jarda Fous (the most active diamond dust observer in Czechia as of now) was planning a trip to Boží dar at Ore mountains where he managed to capture a doubled CZA. Temperature was oscillating between -10 and -8 degrees Celsius, low stratus clouds were hanging atop of the Neklid ski slope and snow guns were at full blast.
GPS coordinates are as follows: N 50°24.24398', E 12°56.31133'
All pictures were taken between 09:15 and 11:30 UTC. Doubled CZA was observed at 10:55 UTC. Jarda used Nikon D7200 with 8mm fisheye lens for wide angle images and Nikkor 18-105 f/3,5-5,6G ED VR for details.

At first, ice fog with low quality ice crystals only managed to conjure up a 22 degree halo with pahelia.

Later a whole myriad of halos developed - among the 22 degree halo and parhelia, a parhelic circle, colourful CZA with aforementioned doubling, 120 degree parhelia, upper tangent arc with uppercave Parry, upper Tape arcs, supralateral arc, 46 degree halo, Moilanen arc and helic arc could be seen as well. Kern was not observed, nor does it show on pictures and stacks.

Looking forward to all of your comments and remarks.



  1. I could see the double CZA on the Legkoroptika group on FB

  2. wow! great catch! the double cza is much more subtle than the danish one. i wonder if it might be there one some previous display in this "not-so-obvious" form. congratulations Matej !

  3. after more detailed look, i must say that this double cza looks a bit weird to me. it seems sharper than the main cza, and its colors (pink-green) are weird for a halo, but super-typical of white light interferences. i wonder if this is the same type of stuff as the danish case, or if we are seeing something different...

  4. This is pretty awesome, yeah. It looks almost like a different beast altogether to the Danish one. At least it seems to be closer to cza. Can we have b-r also of the other image? Matej, you say this was seen at a specific minute, but the two photos that show the arc are taken in different places.

    1. Hey Marko, it would probably be the best to send you the RAW, here you go: Password is halosrulez.

      I wrote the times as Jarda pointed out. You are correct that the doubled CZA shows on the stack (made from single frames where Jarda did not see the double CZA, that's why he only pointed out one time reference) and the later single frames as well - those were shot at the time when Jarda actually saw it.

      He has loads and loads of shots, I only managed to dig up the double CZA from some of those. I'm sure it would be no problem to send them all to you, or any of you other experts for that matter.

  5. It looks like there could be a 3rd CZA nestled in the main bright one because in the USM pic I can see another faint set of spectral colors

  6. It looks like there's an arc above the CZA as well as the one below it?

    Very-flat-pyramidal plate crystal (like 0.6(prism)-1(upper pyramid)-0, apex angle 176°) can form halos similar to those near CZA seen in Jarda's photos.

    Use convex pyramidal crystal will produce a better simulation result ( than concave pyramidal crystal ) - to form two arcs: a clearer one below CZA, another weaker one above CZA.