What was the huge circle of light around the moon over the weekend??

Answer 1

Ring Around The Moon
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.

Moon Ring Weather Folklore
Folklore has it that a ring around the moon signifies bad weather is coming, and in many cases this may be true. So how can rings around the moon be a predictor of weather to come? The ice crystals that cover the halo signify high altitude, thin cirrus clouds that normally precede a warm front by one or two days. Typically, a warm front will be associated with a low pressure system which is commonly referred to as a storm.
It is believed that the number of stars within a moon halo indicate the number days before bad weather will arrive. Give it a try the next time you observe a moon halo.

Rings Around The Sun - The same phenomena that causes lunar halos can also be observed around the sun. A few photos of solar halos using a Coolpix 995 digital camera. NOTICE: Never look at or photograph the sun directly.

Answer 2

Halos, also known as icebows, are also optical phenomena that appear near or around the Sun or Moon, and sometimes near other strong light sources such as street lights. There are many types of optical halos, but they are mostly caused by ice crystals in cold cirrus clouds located high (5–10 km, or 3–6 miles) in the upper troposphere. The particular shape and orientation of the crystals is responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split up into colors because of dispersion, similarly to the rainbow.

Answer 3

There wasn't a circle of light as such.
What you could see was the light of the sun reflected off the moon and shining through our atmosphere.
Up in the higher levels of the atmosphere there would have been dust or water particles which diffuse the light you can see giving it a corona effect.
Next time its raining at night, take a look at the street lighting.
Its the same effect but not as pronounced due to the size differences.

Answer 4

It was a crystalization of the atmosphere due to the cold, and the light reflecting from the sun onto the moon made it appear like a halo.

Answer 5

It was just light reflection, and a bit of haze.

Answer 6

Ice crystals.

Answer 7

It's called a halo.

http://en.wikipedia.org/wiki/Halo_(optical_phenomenon)

Answer 8

A MOONBOW

Answer 9

maybe dust?