LUNAR CORONAE

A Lunar Corona is a most beautiful meteorological effect, and is best seen when the bright moon, around its FULL phase, is high in the sky; so the full moons of winter offer the best opportunity.

Coronae are often seen when the Moon shines through alto-cumulus clouds, often referred to as 'Mackerel Sky',(because the collection of small cloudlets are reminicent of a shoal of fish!) but can be seen through much higher thin, almost transparent clouds. The effect is of a colourful number of concentric coloured rings, a 'Bull's-eye' surrounding and touching the Moon's disc. Coronae of this nature are produced by light defraction produced by small water droplets or sometimes by tiny ice crystals in clouds, the more uniform the size of the droplets or crystals are the cleared the coronae seem to be.

A Lunar Halo is quite different, and consists of a discrete ring or 'halo' some distance away from the moon. They occur usually when the Moon is shining through Cirro- Stratus clouds. Cirro-stratus clouds are often the heralds of weather fronts which frequently bring rain. As with lunar coronae, they are best seen around the time of Full Moons during the Winter months.

LUNAR HALO.

WEATHER LORE:

'Last Night The Sun went pale to bed;
The Moon in Haloes hid her head.....
T'will surely rain- I see with sorrow,
Our jaunt must be put off tomorrow.'

(Erasmus Darwin, from poem: 'Signs of Rain.').
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'The bigger (and brighter) the ring,
The nearer the rain!'

(An old weather saying),

'Circle near, water far;
Circle far, water near.'

(An old Italian saying.)

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'For I fear a hurricane:
Last night the Moon had a golden ring,
And tonight no moon we see.'

from 'The Wreck of the Hesperus'
by Longfellow.

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'A halo around the Moon is a sign of wind'.

(Chinese saying.)

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'Double or treble circles around the Moon foreshadow rough and severe storms, and much more so if these circles are not pure and entire, but spotted and broken.'

(Francis Bacon)

and finally, on this theme, a poem from Aratus:

'A halo oft fair Cynthia's face surrounds,
With single, double, or with triple bounds;
If with one ring, and broken, it appear,
Sailors beware! the driving gale is near.
Unbroken if it vanishes away,
Serene the air, and smooth the tranquil sea.
The Double halo boisterous weather brings,
And furious tempests follow triple rings.
These signs from Cynthia's varying orb arise;
Forewarn the prudent, and direct the wise!'