Skywatchers could be in for a treat tonight, with a 'supermoon' set to light up the skies over Norfolk.

But, with wet weather forecast for part of the day, those hoping to see what can be a spectacular sight, will be hoping the clouds have cleared after night falls.

Andy Gardiner, from the Norwich Astronomical Society, said a so-called 'supermoon' happens when the moon comes slightly closer to the Earth in its orbit than usual.

He said: 'It may look bigger and brighter, but really it's due to an optical illusion called the ponzo effect. If the moon is low on the horizon, then the brain can trick you into thinking it looks massive.

'But the whole 'supermoon' thing is really a bit of a myth. It's not really much bigger than normal.'

The scientific term for the phenomenon is 'perigee moon'.

Full moons vary in size because of the oval shape of the moon's orbit. The moon follows an elliptical path around Earth with one side – the perigee about 50,000km closer than the other – the apogee.

It is the full moons that happen on the perigee side of the moon's orbit which seem extra big and bright and have been dubbed 'supermoons'.

However, with the moon due to be full at just after midday today, those hoping to see the best example of a supermoon may have to wait a little longer.

On August 10, the moon is due to be 863 miles closer than today, while there will be yet another opportunity on September 9.

But for those who are hoping to see the 'supermoon' tonight, Phil Garner, forecaster for University of East Anglia-based Weatherquest, had some good news.

He said, while there would be patchy rain in Norfolk during the day, the clouds should clear as the evening goes on.