This blog post is part of our regular “From the BAA Journal” series. This series features a selection of articles, news, reviews and letters from the Journal of the British Astronomical Association, published six times a year.

This article will appear in the August / September 2010 issue, and is written by Hazel McGee, the Journal Editor.

Setting up on Anaa south, by Hazel McGee

The solar eclipse of 2010 July 11 always promised to be a logistical nightmare to observe. The Moon’s shadow first touched the Earth in the southern Pacific, encountering land at Mangaia in the Cook Islands only after 1450km of open ocean. The narrow track of totality then swung northeast, passing tantalisingly close to the islands of Tahiti and Moorea, which experienced a 98% partial eclipse. Beyond Tahiti the track crossed the Tuamotu archipelago of French Polynesia − thousands of tiny coral atolls, of which very few are inhabited, and even fewer have airstrips that make them accessible to visitors. The track then sped across 3300km of empty Pacific to Easter Island, known as one of the world’s most isolated inhabited islands, and after another 3700km it finally made continental landfall at sun-set in winter on the rugged and inaccessible coast of Chile. Crossing the Andes, the shadow left the Earth after entering Argentina at the tourist resort of El Calafate, where the eclipsed Sun was a mere 1° above the mountainous horizon.

According to NASA, nowhere on the track had weather prospects better than 50% of cloud, but the Tuamotus offered the best chances, with Easter Island notoriously experiencing its rainy season in July. Two major UK-based expeditions both based their operations in Tahiti, with its substantial tourist infrastructure, and chartered aircraft to travel to three inhabited atolls within the eclipse path. For a report by John Mason and Nick James on Hao atoll, see this asssociated blog post.

Astro-Expeditions, led by Brian McGee, Declan Foughnan and Sheridan Williams, carried a total of 160 passengers in a shuttle service of ATR-72 and ATR-42 planes to the tiny Anaa and Hikueru atolls, with a resident population of around 450 people (Anaa) and 150 (Hikueru). With two years to prepare for the event, the locals were looking forward greatly to the party! The population of Anaa took the opportunity to upgrade their home-based visitor accommodation, and each four-person group was housed with a local family for the one or two nights they spent on the island. On Hikueru the visitors stayed in ‘fare potee’ buildings, wood and palm-thatched longhouses specially constructed for the event.

Two observing sites were used on Anaa, which lay N−S across the eclipse track. Most people were based on the north of the island close to the village and airport, and around 20 of us rode in small local fishing boats (with large outboard motors!) to the south of the atoll, where the journey of almost 20km was predicted to provide an additional 44s of totality.

Wading through the cool waters of the lagoon, we joined the boats at first light on a promising morning, with large patches of clear sky interspersed with drifting cloud, and the troublesome wind much reduced from the day before. An exhilarating three-quarter hour speedboat trip brought us to probably the most idyllic eclipse site any of us has experienced: a classic ‘desert island’ beach of firm coral sand and shells, groves of coconut trees providing shade and shelter from the wind, and the quiet waters of the (improbably blue) lagoon lapping gently on the shore. Our local hosts cut coconuts for us to drink, and tiny hermit crabs scurried about, jumping instantly back in their shells should a shadow fall across them, whether of a passing human, or of course the Moon.

First contact was seen at around 07:19 local time (17:19 UT) with the usual mixture of excitement and relief. During the long partial phase the weather was worrying, for the scattered cloud seemed to be increasing, with large patches frequently hiding the Sun for minutes at a time. At second contact, predicted for 18:32:33 UT at this location, the diamond ring shone through a few wisps of cloud but thereafter it remained clear until several minutes after third contact, when cloud covered the Sun again.

Shadow bands rippled across the sand for ten or twenty seconds before second contact, wider, darker and more sharply defined than those in Libya in 2006. (Others also saw them after third contact, but I forgot to look). Then the glorious corona was upon us, two helmet streamers like monkey’s ears at the top of the Sun, and an immensely long streamer below, full of delicate structure like petals in the sky. Through binoculars a string of prominences graced the right-hand limb. With the naked eye only Mercury was visible − the sky was quite bright, and Orion above the Sun could not be seen. I looked briefly with binoculars for Comet C/2009 R1 McNaught) between Mercury and the Sun but as expected, this also was not seen.

All too soon the pink chromosphere and a huge floating prominence appeared on the
left side of the Sun, binoculars were lowered for a massive, lingering diamond ring, and totality was over. That night the villagers and children of Anaa laid on an unforgettable drumming and dancing pageant in the sports hall, full of joyous local colour, and enjoyed as much by the locals as by ourselves.

Later we heard that our colleagues at both the northern Anaa site and on Hikueru had
shared our experience of ‘scary cloud’ but in both cases it had cleared in time. News from Hao atoll was also good, and then later from Easter Island and even from the cloudy midwinter Argentinian Andes: a remarkable sequence of success for a most memorable eclipse.