A mild spring night, a full moon and high cirrus clouds moving across the sky give us the perfect conditions for a lunar corona.
Cirrus clouds are formed so high in our atmosphere, they are made completely of ice crystals.
As thin, wispy clouds pass between our eyes and a bright moon, it becomes surrounded by an auroral disk and multi-colored rings. This is called a lunar corona.
It is formed as all those tiny ice crystals within the cirrus clouds scatter the moon’s light.
Depending on the size of the ice crystals in different clouds passing in front of the moon, the corona may shrink or expand. The smallest crystals will make the largest corona. Microscopic water droplets, pollen spores and any small particle can form them.
Solar coronas are harder to admire, since looking directly into the Sun can be very damaging to the eyes.