glory effect
A glory from monosized droplets has four or more rings. A distribution of droplet sizes causes the rings to become less distinct. A variation of 10%* reduces their contrast and all but the innermost ring is washed out when the variation is 20%.
corona effect
The ring around the Moon is caused by the refraction of Moonlight (which of course is reflected sunlight) from ice crystals in the upper atmosphere. The shape of the ice crystals results in a focusing of the light into a ring. Since the ice crystals typically have the same shape, namely a hexagonal shape, the Moon ring is almost always the same size.Less typical are the halos that may be produced by different angles in the crystals. They can create halos with an angle of 46 degrees.
Sundog/parthelia
Sundogs, sometimes called Sun Dogs, Parhelia or Mock Suns, are with the 22º halo, the most frequent of the ice halos. They are most easily seen when the sun is low. Look about 22° (outstretched hand at arm's length) to its left and right and at the same height. When the sun is higher they are further away. Each 'dog' is red coloured towards the sun and sometimes has greens and blues beyond. Sundogs can be blindingly bright, at other times they are a mere coloured smudge on the sky. They are visible all over the world and at any time of year regardless of the ground level temperature. In Europe and North America one will be seen on average twice a week if searched for.
halo
22º radius halos are visible all over the world and throughout the year. Look out for them (eye care!) whenever the sky is wisped or hazed with thin cirrus clouds. These clouds are cold and contain ice crystals in even the hottest climes.
The halo is large. Stretch out the fingers of your hand at arms length. The tips of the thumb and little finger then subtend roughly 20°. Place your thumb over the the sun and the halo will be near the little finger tip.
The halo is large. Stretch out the fingers of your hand at arms length. The tips of the thumb and little finger then subtend roughly 20°. Place your thumb over the the sun and the halo will be near the little finger tip.
sun pillar
A sun pillar is a vertical shaft of light extending upward or downward from the sun. Typically seen during sunrise or sunset, sun pillars form when sunlight reflects off the surfaces of falling ice crystals associated with thin, high-level clouds (like cirrostratus clouds).
hole-in-a-cloud
A fallstreak hole, also known as a hole punch cloud, punch hole cloud, skypunch, canal cloud or cloud hole, is a large circular gap that can appear in cirrocumulus or altocumulus clouds. Such holes are formed when the water temperature in the clouds is below freezing but the water has not frozen yet due to the lack of ice nucleation particles . When a ice crystals do form it will set off a domino effect, due to the Bergeron process, causing the water droplets around the crystals to evaporate: this leaves a large, often circular, hole in the cloud
rainbow
A bow or arc of prismatic colors appearing in the heavens opposite the sun and caused by the refraction and reflection of the sun's rays in drops of rain.
fire rainbow
A halo phenomenon consisting of a colored arc, red on its upper margin; it extends for about 90° parallel to the horizon and lies about 46° below the sun
aurora borealis
Aurora Borealis is a well known light display in the Northern Hemisphere created by colliding charged particles in the atmosphere. A popular place from which to watch the lights is Alaska. The best time to see Aurora Borealis is between December and March.