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Colourful arcs arising from illumination of raindrops by the Sun rays, refraction and reflection. Czech version available.  
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Halo phenomena

Halos, colourful arcs and sundogs are produced by the refraction and reflection of light in airborne ice crystals. Czech version available.
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Diffraction phenomena

Light diffraction causes vivid coronae, iridescence and glories around the Sun or the Moon. Czech version available.
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Noctilucent clouds

Rare clouds in the upper atmosphere. The season around the summer solstice in high latitudes is the most favorable for spotting them. (Czech)
+ Czech observations, NLC monitor
Gallery news - January, 2008
Complex halo display in Destne
(Photo by Radek Svoboda)
Halo display in Destne
One of the most striking halo displays of recent years in the Czech Republic was observed on December 25, 2007 in Destne in the Orlicke Mountains. Diamond dust halo phenomena highlighted the sky shortly after 12 local time (CET) and lasted until sunset. While skiing, Radek Svoboda took several shots with his cell phone camera and captured a variety of halos including rare ones like Tape arc (Parry supralateral arc) and heliac arc. After the inspection of rest of the photos, even diffuse arcs turned up.

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Gallery news - February, 2006
Circumzenithal arc in Prague
(Photo by Tomáš Tržický)
Circumzenithal arc
The photo shows a brilliant circumzenithal arc, one of several halos and arcs observed during a spectacular halo display in Prague, Czech Republic, on February 3, 2006. This lovely arc was accompanied by bright sundogs and fragments of the parhelic circle. Circumzenithal arcs can be viewed when the Sun's elevation is lower than 32° above the horizon. Hexagonal plate-shaped ice crystals having a preferred orientation are responsible for these arcs. Their vivid colors are produced by the refraction of light rays passing through the 90° prisms of the oriented plates - light enters upper horizontal faces and passes out through vertical sides.

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Gallery news - February, 2005
Subsun (Photo Rene Kajfosz)
Rene Kajfosz photographed this bright subsun on the freezing morning of February 5 in Nýdek. Diamond dust ice plate crystals floated with their horizontally oriented faces acting as tiny mirrors. The display was enriched with bright parhelia produced by the same oriented crystals. Subsuns can be spotted most often from airplanes or mountains.

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Gallery news - January 31, 2005
Sun pillar (Photo Vladimír Odvářka)
Sun pillar
The evening of January 30 was a photographic harvest for Vladimír Odvářka who saw this very bright sun pillar at sunset near České Budějovice, Czech Republic.
Sun pillars are quite common halo phenomena but such bright ones are less usual. Sun pillars are formed by the reflection of sun rays from faces of horizontally oriented ice plate crystals floating in the air.

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Gallery news - January 10, 2005
Iridescence (Photo Martin Poupa)
Cloud iridescence
Vivid colors of iridescent clouds covered skies above central Europe on January 8, 2005. Diffraction and interference of light lighted up edges of thin clouds formed by uniform sized water droplets. The photograph was taken by Martin Poupa in Šumava Mountains.
Short video was taken in Prague.

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Gallery news - December 20, 2004
Altocumulus lenticularis (Hydronet.cz)
Giant Mountains lens
A lens shaped cloud "altocumulus lenticularis" over the Krkonoše (Giant) Mountains on November 10, 2004. It was formed by wind forcing air over the mountains and inducing vertical waves in the downstream. The cloud marks the highest part of a wave where rarefaction causes moisture to condense and then evaporate as the air moves downwards again. While the air moves rapidly, the cloud, the condensation zone, stays stationary.
Video shows development of the cloud between 13.25 - 14.30 CET.
Credit: Hydronet.cz.

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