Ordinary Meeting, 2007 October 21
Where To Go for the 2008 Solar Eclipse
Mr Williams explained that, of the total solar eclipses which would be taking place over the next few years, the one which he would most readily recommend members to travel to see was that of 2008 August 1, despite its comparatively short duration of only 2m27s. The principal reason for this recommendation was that the statistical chances of getting clear skies along its track were significantly higher than for any other eclipse in the coming decade.
The eclipse would begin in northern Canada, track northwards into the Arctic, pass over the North Pole, head south into Russia, and skirt along the border between Mongolia and China before terminating in China. In the NASA 2008 Eclipse Bulletin1, Espenak and Anderson had calculated the statistical probability of cloud cover for each location along this line in August. The prospects in Canada and the Arctic were not good: Cambridge Bay, at the start of the eclipse track, had a 65 per cent chance of cloud. This rose to 75-85 per cent at more northerly latitudes. However, the prospects in Russia and China were better: the chance of cloud cover reached a minimum of 30-35 per cent around Hami in the Gobi Desert in China.
With this in mind, the speaker had set out on an expedition in 2007 August, exactly one year before the eclipse, to explore possible observing sights in this vicinity. His findings had been presented in a recent Journal paper2. In summary, of three sites surveyed – Novosibirsk in Russia, the Gobi Desert in China, and the Altai Mountains in Mongolia – the Gobi Desert seemed the best choice, offering both good weather prospects and some dramatic scenery.
Mr Williams went on to compare these prospects with those for the eclipse of 2009 July 22, which had a much longer duration of 6m39s, but which would be taking place over cloudier parts of the globe. This eclipse's path would start in India, cross Nepal, Bangladesh, Bhutan and China, and then move into the East China Sea before terminating in the Pacific Ocean. The first portion of this track had a 65-85 per cent chance of cloud cover; the eclipse would be taking place during the summer monsoon season. Even in China and on small islands to the south of Japan, the chance of cloud cover would never be below 50 per cent. The best chances of seeing this eclipse would come to those on Pacific cruises, who could sail to find breaks in the cloud.
The next total solar eclipse after this would take place on 2010 July 11, and would have a duration of 5m20s. Its path would be almost entirely over the Pacific Ocean, however; apart from a few islands, its only landfall would be a brief touch upon Chile and western Argentina at its termination. The best land-based observing location would be Easter Island, but even here there was a 50 per cent chance of cloud. The prospects were little better for the 4m02s eclipse of 2012 November 13, whose track would also be over the Pacific Ocean for most of its length; it would be observable from north-eastern Australia, but there was a 40-50 per cent chance of cloud cover there.
Looking further ahead, however, the speaker could strongly recommend the eclipse of 2027 August 21 to those who liked to plan ahead. It would have a maximum duration of 6m23s, and its track would pass through northern Africa, where the chance of cloud cover reached a minimum of only a few per cent in Luxor in Egypt.
Following the applause, the President welcomed Mr Nick James to present Sky Notes.