Skywatchers ready for 'supermoon'

A "supermoon" will grace the skies on Saturday night, with the satellite expected to appear in its biggest and brightest form this year.

The phenomenon, known as a perigee full moon, is likely to cause higher tides as it reaches its closest point to Earth.

At this time it could appear up to 14% larger and 30% brighter than when it is farthest from the planet, experts said. But skywatchers will need a keen eye and clear weather to notice a significant difference - and they may have to stay up late.

The Moon is expected to appear at its best in the early hours of Sunday, at around 4.30am. This will come just after it hits perigee, the point in its orbit when it is closest to Earth. At this stage, it will be around 356,400 km away - compared to an average distance of around 384,000 km.

Dr Robert Massey, of the Royal Astronomical Society, warned the "relatively uncommon" celestial event may not amount to much.

"The eye is so good at compensating for changes in brightness that you simply don't notice (that element) so much," he said. "What you may notice is that the Moon will be a little bit bigger."

But he said it could still be worth glancing up at the skies adding: "The Moon is always beautiful and a full moon is always dramatic."

Scientists have dismissed notions that the phenomenon could cause bizarre behaviour or natural disasters. Its most significant impact is likely to be on the tide.

"When the Moon is closest to the Earth and full or new, you get an increase in the tidal pull in the ocean because the gravity of the moon and the sun line up," Dr Massey said.

The Moon's distance from Earth varies because it follows an elliptical orbit rather than a circular one.