Circumhorizon and Infralateral Arc captured by Bryce Bradford (more images). ęBryce Bradford, shown with permission.

The immense and colourful circumhorizon arc made by plate oriented ice crystals is seen when the sun is high. It stretches from beneath the sun partially around the horizon and always at the same altitude.

The infralateral arc produced by sunlight passing between the side and end faces of column crystals occupies almost the same position in the sky when the sun is high.

It is very difficult to tell the arcs apart in a photograph especially when only a fragment is visible.

Here - unusually -
both arcs are present. The upper arc is the infralateral. Unlike the circumhorizon arc, it is not parallel to the horizon but climbs slightly higher in the sky at its ends.

The 46° circular halo would also occupy a similar position. However, it is much too rare and faint and is almost never seen in these circumstances.


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