Willkommen bei Paraselene.de


0 Pages
Graphic: Symbol MemoPad.


Ice Halos

Ice halos are produced by refraction and/or reflection in ice crystals in the air. The crystals are hexagonal plates and columns. More rare pyramidal crystals produce very special halos. The particular types of ice crystals present in the clouds and their orientation determine whether a particular halo is seen and how bright it is. The solar elevation is also an important factor. Some halos change their aspect with solar elevation or cannot occur at all when the Sun is not high or low enough.

A fairly common halo: 22° halo

A fairly common halo: 22° halo

Some halos are quite common and occur on average a hundred times a year, some are very rare, depending on the light path, the concentration and quality of the crystals involved. Halos may occur separately or in large halo displays involving five or more different halos. They may be incomplete or complete. According to the prevalent crystal shape, certain halos, such as bright parhelia and the circumzenithal arc, often occur together

Halos caused by refraction can be very colourful since the ice crystals act like a prism. Halos caused by internal reflection like the parhelic circle may have blue or red diffraction fringes which have nothing to do with the halo itself. The fringes are similar to a corona and are produced by very small ice crystals too small to produce clean halos - or supercooled water droplets. These crystals or droplets are not always present.

Whenever watching and photographing halos, protect your eyes, never look directly at the Sun in order to avoid eye damage. Always wear sunglasses and choose a location from where the Sun itself is hidden by a tree, a building or something else. You can also use your hands to block the Sun provided that you shield BOTH eyes. Digital cameras may also be damaged by the bright light. Sometimes a neutral density filter can be useful.

Not all kinds of halos are currently shown on this site! Some halos are extremely rare and I await their appearance!

Common halos:

Parhelia (‘sundogs’, ‘mock suns’)
22° Halos
Circumzenithal Arcs
Upper Tangent Arcs
Circumscribed Halos
Light Pillars

Less common or rare halos, among others:

Parhelic Circle
120° Parhelia

Supralateral Arc
Infralateral Arc
Lowitz Arcs
Lower Tangent Arc
Circumhorizontal Arc
Pyramidal halos and their parhelia
Parry Arc
46° Halo
Moilanen Arc
Heliac Arc
Tricker Arcs
Subhelic Arc
Wegener Arc
Hastings Arc
Kern Arc

Above: South pole halo crystals, images by ©  Walter Tape shown with permission.

Grafik: URL dieser Seite.
Permanent link:

nach oben