Expedition of Patrick Poitevin
Tennant Creek, Australia 16.02.1999:
Annular Eclipse of the Sun with the Aboriginals
On 16 February 1999 there was an annular eclipse of the sun. You will find more information about this eclipse in the Hemelkalender 1999. For many people, this eclipse was of no importance, because the coming total eclipse of 11 August 1999 will be the revelation for most people. However, I think they are wrong. The Annular eclipse of 16 February was rather special since the annular total eclipse of 30 May 1984. The size was 0.99277 (or 40 seconds annuarity) and in comparison with others of the same kind rather big. This means: a very short duration of maximum (or annularity) and consequently also a very thin ring. The moon's profile reveals itself more and better and you will be able to better observe and follow the Baily's beads. It will last until 10 June 2002 before we will have a bigger magnitude for an annular eclipse. It will be a magnitude of 0.9962 or 23 seconds annularity.
This eclipse of 16 February was only visible in Australia. The central line ran from Geraldton at the west coast to Cairns at the eastern coast. The biggest magnitude and shortest duration could be observed at the western coast. The weather predictions were the best over there. Reason why most of the eclipse chasers chose their observation site in the neighbourhood of Geraldon. Moreover, Geraldton could be easily reached from Perth. For me (Patrick Poitevin) and Jo (Joanne Edmonds) however, a reason not to travel over there and avoid the eclipse fuss. We chose Tennant Creek in Northern Territory for our observation : A little place with some 2000 inhabitants, between Darwin and Alice Springs. The weather forecast was less favourable for that spot and also the duration was only 61 seconds or magnitude of 0.9849. According to the contacts on the Solar Eclipse Mailing List nobody was travelling to this place. So enough reason for us to observe the eclipse there.
At our arrival in Darwin we discovered that a hurricane had called in at Cairns. For the following days rain had been predicted. We moved to the south in a campervan, in the direction of Tennant Creek. Fortunately, the rain was not noticeable. The weather pattern was more or less the same every day. In the morning beautiful and clear weather and as the afternoon went by more clouds appeared in the sky. The nocturnal sky could be observed unclouded. A splendid sky on camping sites with no light. But unfortunately, the eclipse was going to take place in the late afternoon, and by all odds in the clouds, if this pattern would persist.
The day before the eclipse we arrived in Tennant Creek. We looked for an observation site. There were not many options. The main road from Darwin to Alice Springs and further on to Adelaide ran through Tennant Creek. There was only one side-road that further on eastwards would cross the central line. Previously, we had already drawn the lines thoroughly on a good regional map. This seemed necessary because a general map of Australia mentioned the co-ordinates wrongly, so that Tennant Creek did not fall at all in the central zone.
Because the annular eclipse would be a very short one and as the ring itself would be very thin, we did not want to observe on the northern or southern border. Thanks to the GPS and the good map, we sought the central line and thus found a magnificent observation site : an open horizon for 360 =B0 and a place where nobody could disturb us. Except for the usual visual and photographic work with our two Celestron C90 telescopes (both 1000 mm focal length), we brought a big white sheet that we spread out for any possible shadow bands before second or after third contact. From Minolta I got a colour meter on loan. Thanks to this instrument, we could register the colours in L.a.b. values, which means the light intensity, but also the measurement on the red-green and the blue-yellow scale. Of course I also took my dictaphone for any possible animal sounds and our own impressions of the event.
The day before the eclipse the sky was clear at the moment that the eclipse would take place. That was promising ! That evening we met Valentin and Rita Kinet who originally intended to observe the eclipse in the Central Desert. But due to the weather conditions they had changed their plans and chose a place to the south of Tennant Creek, near a cemetery.
The day of the eclipse
The day of the eclipse did not seem very well. There were a lot of clouds in the sky. Gee, this would be a long day before first contact ! First contact would start at 16h18 (6h48 UT and so 9.5 hour difference) and the maximum at 17h00 local. The sun's altitude for the 4 contacts would be :
I 6h48m16s 39 II 8h00m17s 22 Max 8h00m47s 22 III 8h01m18s 22 IV 9h04m27s 7
So during the day we relaxed. It was just amazing that I did not worry at all about the weather. Obviously, I fully believed that those heavy clouds in front of the occulted sun would disappear at the right moment.
On the observation site we put the campervan in such a way that we got a white wall behind us for any potential shadow bands. The big white sheet was spread out horizontally in front of us. As the first contact approached, the sky opened up. A strong wind seemed to blow the clouds away. An hour before the eclipse we got everything ready. The sun showed many splendid groups of spots. There was even one big spot, which we managed to see with only eclipse glasses on. These groups and spots constituted already a spectacle in the sky. They made the partial phase of the eclipse very enthralling.
Jo saw first contact of the moon with the sun while I was busy doing measurements with the colour meter. I made the first record at 6h55 UT. The sky was beautiful and clear and the temperature amounted to more or less 45C. The flies did not give us a moment's rest and the crickets sounded softly in the background.
One sunspot after the other disappeared at the dark moon's edge. It was a beautiful partial phase. The moon's profile was well seen. Due to the strong wind, the edge sometimes seemed turbulent, but it turned out better than we had expected. Jo already saw at a magnitude of 0.35 that the colours of the scenery were changing. The complete underground was very red and clear. But indeed it became less intense red. From then on we could follow the ranges of colouring and the light intensity very well. It grew darker and the colours changed to deep red and the sky to a grey blue. The sky was not completely without clouds. Behind us clouds turned up sometimes. A big cloud approached the semi-occulted sun at about 7h02 UT but seemed to split up in parts as it came nearer to the sun. A haze remained around the sun, which gave cause to a halo.
Through the telescopes and the eclipse glasses we were able to follow the sun constantly. It was magnificent. The big spot needed more than three minutes before disappearing behind the serrated moon's edge. We could se= e and follow Venus early, but the planet disappeared quickly in the surrounding thin trails of clouds. Venus was almost 30 minutes before maximum visible in the sky. It was now 7h34 UT. The shadow became more faint and blurred. Little crescents were thrown on the white wall of the campervan. Jo sometimes saw a crescent flying over the white side. Those were the shadows of the flies, thrown in the shape of a crescent on the campervan. It was the first time that I saw such flying crescents during a partial eclipse. If that was not a spectacle!
We saw no shadow bands. Neither on the white sheet nor on the white wall. Second contact approached and at the extremities of the terminator we saw the last sunlight breaking off. The crickets began to make a lot of noise. Were they also that excited due to this beautiful eclipse of the sun? A bird sounded rather confused in the background. It was already very dark and then all went quick. Our shadows were vague and spooky. It grew a little bit cooler. The flies were a lot more aggressive. They adopted an attacking position while before; they only came sitting on us. At the right side of the sun the halo showed a little rainbow. Sometimes the halo could be seen for 120 degrees. The horizon was unreal and had a strange colour. For one instance we discovered a sundog. We were not able to follow everything that could be seen. The profile was ultra thin.
Second contact ! What a thin ring. Oh so beautiful and so thin. The interruption was beautiful. So we were in the middle of the central line. That was satisfying. The path was only 65 kilometres broad. It passed very quickly. How beautiful. The moon's relief was already visible from the partial phase. Now with the thin ring it was also the case. Without a filter it was not possible to look at the sun. We tried to photograph it with short times of exposure. Once more it was proved how much luck you need at solar eclipses. Afterwards we heard that our colleagues Valentin and Rita Kinet only saw a cloud in front of the sun during maximum. They were hardly a short distance further on to the south of Tennant Creek. But consequently they missed all of maximum. From our observation site this was the little cloud underneath the sun.
The halo was still there. The flies still were aggressive. After third contact the sunspots reappeared one by one. No shadow bands were seen after third contact. For us it had been a successful eclipse, which we had been able to follow from first to last contact. And this in spite of the thin haze around the sun. Two days after the eclipse we could see the narrow moon crescent at more or less 1 degree from Venus. A beautiful conjunction, just like the conjunction of Venus and Jupiter that same week. It was a successful trip. Now we can finalise the preparations of the following on 11 August. Iran, here we come.
7A The Drift, Rowlands Castle, Havant
Hampshire PO9 6DG, England
Tel. +44 (0)7968 1940 88
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Many thanks to the dedicated work of Patrick Poitevin for making these files available.
7A The Drift, Rowlands Castle, Havant
Hampshire PO9 6DG, England
Tel. +44 (0)7968 1940 88