There's two supermoons occurring this month. Here's when you can see them

Two supermoons will grace our skies this month, with the first set to peak tomorrow on Wednesday, August 2 - with what's known as a sturgeon moon. 

The moon’s closest approach to the Earth will be at 4.32am Wednesday (AEST).

Then, at the end of the month, there will be what's known as a "blue supermoon" (although it won't be coloured blue), on August 31.

The blue part comes from the term for two full moons occurring in one calendar month, a pretty rare occurrence only happening every 32 months or so.

A supermoon occurs when a full moon happens at the same time as the Moon's orbit brings it closest to Earth. This is called the perigee.

When this happens, the Moon is just 363,396km from Earth, which makes it look bigger in the sky. This is the opposite of what's known as the apogee, when the Moon is 405,504km from Earth.

A supermoon happens when a full moon occurs at the same time as a perigee, and is generally applied when the Moon is 90 per cent or closer to its perigee.

And, in case you were wondering why tomorrow's event is called a sturgeon moon, this is a unique Americanism given to a full moon in August, and named after the historically large numbers of sturgeon fish that were found in the Great Lakes in North America at this time of year.

The only other supermoon this year will be on Friday, September 29.