Plate shaped crystals in high and cold cirrus cloud produce the summertime halo
Rare in Europe - Circumhorizon Arc
Denis Joye captured this halo near Paris on 31st May '11 before his viewing was curtailed by a fast moving lower cloud.   ©Denis Joye, shown with permission.

About - Submit Optics Picture of the Day Galleries Previous Next Today Subscribe to Features on RSS Feed

The circumhorizon arc (CHA) needs the sun higher than 58° which in mid to northern Europe means that it can only be seen for a few days or weeks around the summer solstice.

In June and early July check daily around noon below the sun and near the horizon.

Dates of visibility.