Night skies above eastern Australia were lit up by a spectacular sight on Sunday night, with a strong moon halo captured by numerous members of the Weatherzone gang.

Image: Mmmmm.... sky donuts. Source: @Ssungwoopark via Instagram.

A lunar halo is a large bright ring around the moon. In reality, there’s not actually a ring there. Lunar halos are optical illusions caused by the refraction (splitting) and reflection of moonlight off ice crystals suspended in wispy cirrus clouds in the upper atmosphere.

Fun fact 1: Halos always have a radius of 22 degrees. And there's a pretty cool way to check this. According to earthsky.org, if you hold out your hand at arm's length to the night sky, the distance between the tip of your pinky and thumb should be about 25 degrees. So it should be just wider than the distance between the moon and the halo.

Fun fact 2: There's an old saying that goes: "ring around the moon, rain soon". The fairly simple logic here is that high cirrus clouds often precede wet weather. And as we've been predicting for several days now, there is indeed wet weather in store later this week for eastern Australia, and especially the southern half.

Source: Geraldine Fasso @geds_photos via Instagram.

So why the halos on Sunday night?

If you look at the Monday afternoon satellite image, you can see loads of cloud over the eastern half of the country, but not too much in the way of rain (the green blobs). That suggests a fair amount of high cloud, and conditions similar to Sunday night.

So who knows? With all that rain-free cloud sticking around on Monday arvo, perhaps this Monday evening will be another good time to say hello to a moon halo?

If you see one, feel free to share your pics by using the hashtag #Weatherzone on your post and we'll throw the best ones into this story and might even make a fresh post on social media featuring your work.