An impossible eclipse at the end of the world

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And then the shadow came, racing towards us with supersonic speed, almost grazing the Earth's surface and about to lift off into space again after having swept through a vast stretch of the Pacific Ocean in the hours past. The Sun was ten minutes from setting, a dazzling orange beacon hugging the horizon under a deep blue sky, devoid of any clouds except some in the far distance over isolated Andes mountains. And this sky was about to change in a swift and dramatic fashion only experienced during total eclipses and only when they take place with the Sun a mere few degrees above the horizon. Most astonishingly, however, we were there to witness it all, perhaps a hundred right here: amateur astronomers having travelled half-way around the world and locals alike. In the middle of winter, 80 km East of the little town of El Calafate in Argentina's Santa Cruz province in the heart of Patagonia - and, the most unexpected turn of events of all, with perfectly clear weather. The place was a mirador, just a small parking lot at a kink of route 11 where the view of the Andes panorama was best - that's the reason people normally stop here. For the grand finale of the total solar eclipse of 2010 this spot at over 800 meters elevation overlooking lower steppe and the Lago Argentino towards the North-East had become one of very few locations all around from where the fully eclipsed Sun would be seen well clear of the Andes peaks: our tour planner had found out about it via Google Earth, the locals knew it anyway.

There had been hardly any advance news coverage of the eclipse - coinciding with the final game of the world cup - in the Argentinian media, and so just a handful had flown in from the North: It were mainly individual eclipse chasers and tour groups from distant countries that had converged here, foregoing the even more remote and expensive islands in the Pacific the Moon's umbra would touch and settling for a totality practically at sunset, something few have ever seen. Let alone with clear enough skies to see the major features of totality - the corona, chromosphere and prominences - well. It had happened in an Australian desert in 2002 and in Antarctica in 2003, though, but under very different conditions: in Oz the umbral cone was extremely narrow as Moon and Sun had almost the same angular size, in Antarctica the eclipse happened practically at midnight, with the corona grazing the horizon. Apart from the vague expectation that a big-umbra eclipse near the horizon might provide similar effects, little did we know about what would happen now in frozen Patagonia. Before arriving in El Calafate hopes had been kept in check anyway: 'Offical' weather reports showed mainly dull days with snow or rain, and adding in the low solar elevation there simply would be no chance for any clear view of the eclipsed Sun. Funny sky illumination effects maybe, but anything beyond that?

Alas when we arrived late on July 9th, fellow eclipse chasers told of dazzlingly bright sunsets and even had HD video to prove it. After horrendous snowfalls in late June, July had seen several extremely clear days, and the eclipse would have been seen well perhaps every other day or so! Both the 10th and 11th had ample sunshine indeed in the mornings (with sunrise at 9:45 local time, a strange experience), though on the 11th it had become overcast around noon. Yet after the - invisible - sunset the clouds had gone away, and e-day then had stayed clear throughout. Very clear indeed: From our vantage point mountain tops 160+ kms away were clearly seen, and the Sun, even sinking lower, just turned a bit yellow but hardly lost any brilliance. First contact came at 16:44 local time, with 64 more minutes to go until totality: Combined with the slowly sinking of the Sun towards the Andes, it took a long time until the eclipse could be 'felt'. A general fading of the light beyond a typical late afternoon was evident around 17:30 perhaps, and the temperature - until then surprisingly bearable - started to fall. All that was not too different from a 'normal' total eclipse of the Sun higher in the sky, but eventually new phenomena appeared in the sky I had never seen before.

The Sun was now sitting in the west-north-western direction, about 2 degrees high - actually it should have been around 1°, but refraction and being on high ground added another degree or so. To the right (North) of it the Andes peaks were seen silhouetted against a normal evening sky. But to the left of the Sun, looking about due west, the sky color pattern had turned drastically different. Here now the mountains (and isolated clouds above them) were in darkness, seen against much more dramatic sky colors with intense green and orange hues veterans would recall from earlier 'high' eclipses. But above that a sharply defined finger of darkness arose - the very lunar shadow itself! With high eclipses you may note a general darkening of the sky in the direction from where the umbra is coming or perhaps feel a dark wall approaching - but this was totally different. And, despite the much broader umbra, surprisingly similar to what was seen in Australia in 2002. Now everything happened at once (and I make use of my photographs to order my recollections): The solar photospheric crescent shrinks to a dot, the brilliant last diamond, while the inner corona is already detectable. The umbral finger grows and moves towards the right - and at the moment of 2nd contact the photosphere vanishes and the umbra swallows the Sun.

During the following minute - it has become pretty cold now and fiddling with cameras and binoculars becomes problematic - the great show in the sky turns more and more symmetrical until the eclipsed Sun resides in a huge dark sector centered on it and reaching to the horizon. But to the left and right of it two sharply defined wedges of light of different colors mark the edges of the umbra. Which has also, when you turn around, darkened the sky opposite to the Sun dramatically. The Sun's corona is surprisingly well visible, with all its streamers and even some prominences: badly squashed by refraction and reddened a bit but without much loss of detail. From now on the show reverses (while the Sun still sinks closer to the horizon), and soon the chromosphere appears again, near its lower edge - and ruddier than ever thanks to the extra reddening by the atmosphere. Then suddenly the 2nd diamond ring, the umbra collapsing again into a broad finger moving to the right (north) and the horizon color pattern reappearing in reverse.

Totally stunned by what we had just witnessed - and also pretty frozen by now - we still couldn't call it quits: Some minutes later the Sun would set behind the Andes as a thin crescent, with both horns up! And now - and only now - the extrem transparency of the atmosphere had an actually negative impact: You couldn't look at the Sun even at the exact horizon without a pretty dense filter nor photograph it even with the shortest exposure time. While setting more interesting atmospherical optics phenomena were triggered in that thin orographic clouds (of no absorption power whatsoever) behind the Andes peaks shone up brightly by forward-scattering the last sunlight. And when the Sun - still in deep 2nd partiality - was gone more wild sky colors appeared, making this a brilliant dusky sky that would have brought out the cameras even without an eclipse. At that time we were already moving home to El Calafate - where, intriguingly, the skies clouded up completely in the following hours. And later we would learn that skies as clear as we had had them on 11 July 2010 are seen perhaps five times a year in Patagonia ...

Daniel Fischer, first draft 12 July 2010, on a plane over Argentina and in Buenos Aires

Higher resolution pictures in chronological order:

(Unfortunately TwitPic has since self-destructed by deleting all hi-res images and leaving only the crappy 600 px wide previews - sorry, no one saw that coming.)

One + Two -> observers at the site
Three + Four -> partially eclipsed Sun
Five -> the landscape in deep partiality
Six -> the shadow is coming
Seven -> dazzling diamond ring effect
Eight -> shadow very close to us now
Nine -> seconds before it happens; shadow plus corona seen
Ten -> totality! shadow just swallowed the Sun
Eleven + Twelve -> eclipsed Sun & Andes
Thirteen -> corona close-up
Fourteen + Fifteen -> sky near mid-totality
Sixteen + Seventeen -> before & after 3rd contact
Eighteen -> the shadow is moving away