This week you might have noticed the moon has seemed larger and redder than usual. Last night's was particularly spectacular.

It's called the Harvest Moon, and it's the full moon that rises nearest to the Autumn Equinox.

Usually it happens in September but every four years - including this year - it happens in October. This year's Harvest Moon is the latest since 1900.

So why does it look so big? It's an optical illusion, caused by the fact that the moon rises earlier at this time year.

The human eye perceives a low-hanging moon to be larger than one that's high in the sky because of the tilt of the earth.

The colour of the moon shortly after it rises is also an optical illusion - when the moon is low in the sky, you are looking at it through a more atmospheric particles than when the moon is overhead.

It's called a Harvest Moon because of its connection with the Norse god Loki. It is said to give him his power to bless the harvest.

Farmers also used to use its light to work through the night at harvest time.

Have you taken any pictures of the harvest moon? Send them to us here