Highlands and islands prepare for invasion of eclipse chasers and a once-in-a-lifetime event

Scotland's rugged northern coastline will provide the dramatic backdrop to a once in a lifetime chance to view an annular eclipse of the sun from British shores next month.

Thousands of eclipse chasers are expected to travel to the Highlands and Islands to view the phenomenon at sunrise on 31 May.

As the sun pokes above the horizon off the Caithness coast, crowds are expected to gather on the windswept beaches from Durness to Dunnet Head, the northernmost point on the Scottish mainland.

On Lewis, tour groups from Europe and North America have already laid plans to watch the eclipse from a circle of 12ft-high megaliths known as the Standing Stones of Callanish – a primitive astronomical calendar believed to have been erected by the inhabitants of the Outer Hebrides 4,000 years ago to chart the movements of the stars.

An annular eclipse occurs when the moon covers the centre of the sun but not its edges, so that a spectacular ring, or annulus, of light forms around the moon. The spectacle, which has not been seen from Britain since 1921, will not be visible here again until 2093.

Although a partial eclipse will be visible over parts of Europe, northern Asia and Russia, northern Canada, and Alaska, the eclipse will be best viewed in Scotland from the Orkneys, Shetlands, Lewis, and most of the Highlands, including the capital, Inverness.

Providing weather conditions are clear, watchers in Inverness should see an annular eclipse lasting 1 minute 13 seconds, right on the horizon; in Stornoway, the eclipse will last 2 minutes 24 seconds.

In Iceland, however, the eclipse will last over three and a half minutes, with the sun well clear of the horizon. Starting at about 3.45am and ending at about 5.45am, the path of the moon's antumbral shadow begins in northern Scotland, crosses Iceland and central Greenland, and ends at sunrise in Baffin Bay, Canada. Although annular eclipses occur with a slightly higher frequency than total solar eclipses, they are still quite rare in small islands such as Britain, which makes next month's event even more important.

The Highlands of Scotland Tourist Board is anticipating a busy end to May by encouraging local operators and guest-house owners to promote special packages to attract visitors. David Noble, the board's chief executive, said: "The north coast offers some of the most stunning coastal views with spectacular sunrises, 365 days a year. This is a special place to experience a special natural phenomenon which people won't want to miss."

Sandy Barton, of the Ben Corragh guest house in John O'Groats, was looking forward to the boost in tourism. "Most of the guest houses and hotels around here are full already and have been for some time," he said. "We've got people booked in from all over Britain and Europe and are having to turn more and more people away as each day passes.

"My greatest fear is that a lot of people will turn up without booking anywhere and find they have nowhere to stay."

"This eclipse is undoubtedly good for the area," said Jean Manson, who runs the post office near John O'Groats. "A lot of places have been taking bookings since last year and the number of people ringing up is increasing the closer we get to the event."