Ice Crystal Halos

Lascar display III

Lascar display III

Continuing the Lascar halos tour. This image gives situation for sun elevation range of 11° to 9°. Image is stacked from four photos and also mirrored version is provided. 23° plate arc is already disappearing high up above the sun, but 20° upper plate arc on the other hand is appearing.

10 years ago we simulated the display with octahedral crystals of cubic ice and traditional pydamidal crystals. Octahedral crystal gives halos only at 28° and 19° from the sun. It was a good candidate for simulating because many features in photos from different solar elevations fell in place with it.

Among other things these simulations predicted that the 20° upper plate arc would be actually composed of two arcs, the other one being 19° upper arc… But there are still too many unexplained features in the display to trust our model, one being the fake 18° plate arcs.


  • Have to say the same about the Lascar display the stacking helps solve some of the mystery behind some of the unusual arcs the arc below the sun looks like 9d plate arc but its too for to be that. Hope one day a similar display like it shows up and get more photographs.

    Was this diamond dust of high-clouds?


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