Orwell Astronomical Society (Ipswich)
Solar Total Eclipse, 21 June 2001
Eclipse chasing may seem a bizarre activity but the sight of the eclipsed Sun is truly amazing and almost immediately addictive, and eclipses do provide an excuse to visit exotic and interesting places. Thus it was that on 17 June 2001, feeling a mixture of unease and anticipation, a group of 120 eclipse chasers boarded a plane at Gatwick to fly to Harare, Zimbabwe. (The unease was occasioned by recent press reports of problems in Zimbabwe). The common goal of the travellers was to observe the total eclipse of the Sun that would take place on midwinter's day south of the equator over a narrow strip of land straddling Angola, Zambia, Zimbabwe, Mozambique and Madagascar. The flight landed at the brand new Harare airport, built to handle two million passengers each year, ten times the capacity of the old airport. It was immediately obvious that we were in the southern hemisphere as the baggage carousel rotated clockwise... the one at Gatwick goes anti-clockwise (only joking!). A short bus ride, literally 100 metres, took us to the domestic terminal to pick up the internal flight to Kariba. This is where the size of the group started to challenge the infrastructure of Air Zimbabwe. The biggest aircraft took just 42 passengers, with our flight being in a 17 seater. It took most of the day to transfer everyone to the hotel and one poor soul actually had to be driven overland and arrived mid-evening!
Kariba of course is famous for its lake and dam and the first full day there gave us the opportunity to take a cruise along the shore to spot wildlife. We soon discovered hippos basking on the shore with crocodiles among them... rather worrying when you are on a small boat! We also spotted elephant and a wealth of birdlife.
That night gave us the first sight of the southern constellations. When we left home, Mars was just visible in the murk along the southern horizon. From Kariba, it rose vertically in the east and by midnight was overhead with Scorpio as a backdrop... stunning! The Southern Cross and Coalsack were easily identified but, soon after identifying Alpha and Beta Centauri, my knowledge was exhausted. I determined to buy a southern hemisphere planisphere as soon as I could.
On 20 June we headed for the Zambian border just a few miles away for the journey to Lusaka. Three hours after arriving at the border crossing we finally made it through, one of the delights of travelling between countries that don't get on too well. The delay meant that we didn't arrive at our hotel in Lusaka till after dark. On arrival, after collecting our room key and dumping our bags, we were whisked off to a lavish Chinese meal.
Eclipse day, 21 June, dawned bright, clear and cold. We had ascended to over 1300 m which gave a significant chill to the air before the sun rose high in the sky. Breakfast was laid on in an outside cafe area after which we gathered our equipment together and set off north by 10am. The eclipse site was superb. An ex-pat owns a farm right on the eclipse path and he had cleared several acres of stubble for our group and a large contingent of Americans. In all, 300 people were on site but everyone had plenty of room. Unlike previous eclipses, where we have been in the middle of nowhere with virtually no facilities, this time we enjoyed toilets, a marquee, outside bar, big shady trees and a massive barbecue serving lunch and dinner. The best site I've every been to or heard of...! We set up a camera and then enjoyed lunch at the barbecue.
After lunch we returned to the camera to prepared for 1st contact... There is always a sense of competition to see who first notices 1st contact. As usual it was the Americans who shouted it out although several of we Brits had noticed it slightly earlier but enjoyed the moment in reverential silence. First contact was at 1.42pm and there followed a slow progress of the Moon's disc across the Sun until totality at 3.10pm. The ingress phase of the eclipse was made more interesting by the presence of a large group of sunspots which made the motion of the Moon more obvious. By the time the Moon had moved about half way across the Sun, the light was noticeably less intense and we could remove our sunglasses as the glare was much reduced. With just minutes to go to totality, the light became strangely dim and the air cool. Through the solar filters the crescent Sun started to shrink rapidly. This was the time for photographers to remove the filters from their camera lenses and start taking a rapid sequence of images in the hope of capturing the diamond ring effect. (This occurs when the last point of sunlight shines down a lunar valley as the inner corona becomes visible.) With the last vestige of the intense photosphere gone, the light dropped dramatically and totality began.
And the few minutes of totality is what makes a solar eclipse so special! During totality, we could see the eerie, pearly, blue-white solar corona in subtle but stunning detail and, superimposed upon it, the pink flames of prominences hanging above the solar surface. The corona was in a typical "solar maximum" configuration, evenly spread around the Sun. At the solar eclipse of 26 February 1998 the corona was very different with long equatorial streamers and very fine "polar brushes". These structures arise from magnetic fields at the Sun's poles and mimic the shape of iron filings sprinkled on paper over the poles of a bar magnet. Hard to imagine that they actually stretch many times the Earth's diameter into space!
Staring through a 100 mm telescope at the eclipsed Sun (perfectly safe during totality) time rushed by and a pink rim soon began to appear on one side of the Moon. This was the thin chromosphere of the Sun and heralded the end of totality. Within seconds the bright photosphere began to reappear and we had to cease using the telescope. Totality was over.
The following image shows the inner corona and a large prominence on the right. It was taken by Sue using a 500 mm f/8 Tamron mirror lens at 1/125s on 200 ASA print film.
At either side of totality we clearly saw "shadow bands". These are ripples of light on the ground which look similar to the ripples at the bottom of a swimming pool on a sunny day. They are caused by moving cells of air bending light from the Sun as it becomes almost a point source in the sky.
With the end of totality the Moon slowly began to move off the Sun's disk and light returned to the landscape. But it wasn't quite the same as before. We had witnessed an aspect of the Sun that is always present but rarely seen, and felt privileged.
See Fred Espenak's eclipse web site eclipse.gsfc.nasa.gov/eclipse.html.
Mike Harlow & Sue Brown