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Last Updated: Thursday, 23 June, 2005, 12:21 GMT 13:21 UK
June Moon dazzles skywatchers
Moon over St Petersburg, Russia     Image: AP
Skygazers from St Petersburg (pictured) to the UK could see the effect
Observers were treated to a spectacular show in the evening sky last night when the full moon appeared bigger than it has done for several years.

The effect is down to an optical illusion that means a full Moon close to the horizon appears much larger than when it is high in the sky.

It coincides with the summer solstice, when the Sun is highest in the northern sky and the Moon is very low.

This, and other factors, conspired to make the Moon seem exceptionally big.

During midsummer, at the time of the solstice, the Sun sails as high as is possible across the sky during daytime, while the Moon skims low over the horizon.

Another factor is that the Moon's orbit around the Earth is known to wobble slightly. An 18.6-year cycle in this wobble took the Moon even lower in the night sky than usual for this time of year.

Peter Bond of the Royal Astronomical Society told the Daily Mail newspaper there was an easy way of demonstrating that the effect was just an optical illusion.

"If you hold a coin at arm's length, you can compare it with the size of the Moon and you will find that the Moon stays resolutely the same size in relation to the coin whether it is low or high in the sky," he said.

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