Supermoons are like buses, you wait ages for one, and then three come along at once.
We've already had two this year in July and August and now we'll see another one in the early hours of Tuesday. It's the final one of the year and, in fact, it's the final one until this time next year when the phenomenon of a giant moon returns.
The moon will look larger when it appears in the sky on Tuesday, creating a so-called supermoon that should wow sky-watchers once again.
The moon will appear in almost its biggest and brightest form of the year because its oval-shaped orbit brings it to the point closest to Earth. It won't be quite as large as August's, but that won't be noticeable to the human eye.
Also known as a perigee moon, Tuesday's full moon will be around 14 per cent closer and 30 per cent brighter than when it’s at its furthest point from the Earth.
The moon usually appears at its largest on the horizon due to an effect known as the “moon illusion”. This optical illusion is created when the moon appears in the background against everyday objects such as trees and buildings and, although its not completely understood, it makes the moon appear even bigger - and look good in pictures.
This makes northern Scotland the best place to see the supermoon as this is where the moon appears lowest on the horizon in the UK.
While July was the closest moon of the year, Tuesday's supermoon will also see the moon come extremely close to the Earth - within 10 per cent of the nearest it will ever be - and these near moons are also referred to as supermoons.
This makes it seem that the phenomenon is becoming more common, but it appears in a cycle every 14 lunar months and the next time the moon appears this large will be in September 2015. Last year there were also three supermoons, however only one was widely reported.
Interest in the event was also extremely low before 2011 when it was linked to the earthquake and tsunami that coincidently hit Japan at the same time. Since then, the media has paid more attention to the event, as can be seen in this trends chart.
UPDATE: Now the supermoon's over, check out the best pictures from last night