Orwell Astronomical Society (Ipswich)

Home Events

Solar Total Eclipse, 11 July 1991

2:00am:  it's dark and raining. Struggling out of bed we board a bus. The traffic is moderate as we head to our destination.

3:00am:  we've arrived! But it's still dark and drizzling - outside looks cold and bleak!

You might imagine that I'm describing the journey to Gatwick Airport - but no, this is Hawaii and it's eclipse day!

The eclipse of 11 July 1991 brought a golden opportunity to professional astronomers to study the phenomenon with the advanced instruments at the observatories on the summit of Mauna Kea, Hawaii, which lay almost exactly on the centre line of the eclipse. In addition, many amateurs prepared to travel across the world to Hawaii for what could be the "eclipse of a lifetime".

The travel company that I used, Explorers Tours, offered a choice of two observation sites, one in Mexico and the other in Hawaii. Some two thirds of the 750 or so people who travelled with Explorers Tours chose Hawaii, despite its shorter eclipse duration, perhaps because of the appeal of a "tropical island paradise" in the middle of the Pacific Ocean. Flying the flag for OASI, I too decided to brave the coconut fringed sun soaked beaches, hula dancing and pina coladas but was rather surprised to find myself on a bleak mountainside in the cold and wet! The temperature at sea level on the Big Island, even in the rain, is very comfortable: in the seventies (°F) even at night. As we ascended the mountain, however, it got a little cooler.

The weather conditions would not have come as too much of a surprise in the town of Hilo on the rainy, windward side of Hawaii's Big Island. The twin dormant volcanoes, Mauna Kea (with its famous observatories) and Mauna Loa, at around 4500 m and 4000 m high respectively, encourage rain to fall which makes the windward side of the island wet and lush with tropical rain forest and the leeward side relatively arid and desert-like.

The University of Hawaii, which operates the observatory site on Mauna Kea, decided to close the access road and called in the island's local defence force to operate a road block at 2500 m altitude. As dawn broke on eclipse day we, the "Explorers Tourists", found ourselves sitting in a fleet of yellow school buses parked in front of the road block with drizzling rain and the persistent cloud still above us. As the situation developed from being unpromising to being totally hopeless it was clear that desperate measures were required. Explorers Tours entered diplomatic negotiations, led I believe by John Mason, with the local defence forces. After about 20 minutes of political manoeuvring the local defence forces waved through the yellow buses. (Talking to a local on another, sunnier, island the following week I discovered that it was an event for which we became famous!) At about 2700 m the fleet stopped and the Explorers Tours eclipse chasers poured out, unloading a huge array of photographic and astronomical equipment. The cloud was still a little way above us but looked as though it would disperse sufficiently to observe the event.

As we set up our equipment a man from the road block drove up and down the road at high speed shouting at us for going slightly further up than we were supposed to. We carried on despite this distraction because things were beginning to look promising.

At around first contact (the beginning of the partial phase) the cloud was already thin enough to allow us to start observing. At second contact (the start of totality) we witnessed a single Baily's bead. At totality the most striking feature was a very large prominence that showed as a bright pink arc. The solar corona had an asymmetric appearance more like that which would be seen at solar minimum (in 1991 the Sun is near to solar maximum). The appearance of the diamond ring (the re-appearance of the sun's photosphere) provided a spectacular end to totality.

Later, there was further good news for the group on Mauna Kea, which had come so close to missing the event: at most of the other locations on Hawaii the event had been obscured by cloud. In addition, the observing site on Mauna Kea was evidently close to the centre line as indicated by the fact that totality lasted around 4 minutes and 12 seconds - approximately equal to the maximum possible on the island.

More Information on Eclipses

See Fred Espenak's eclipse web site eclipse.gsfc.nasa.gov/eclipse.html

Pete Richards