Thursday, July 31, 2008

Total eclipse of the heart sun

A partial solar eclipse in  1999
Image Credit: Yours truly

Tomorrow (1 August 2008), the moon will pass completely in front of the sun, at least in certain parts of the world. This map shows where the total eclipse will be visible (shaded dark blue area), and where the sun will be partly eclipsed by the moon (between light blue lines).

Total solar eclipses are rare, happening, on average, about every 18 months. And then notice how small of a portion of the Earth gets to see an eclipse -- a thin strip less than 100 miles wide, though a few thousand miles long. No wonder that any given part of the Earth will only see a total solar eclipse every 375 years or so! If you want to see a total eclipse, you'll probably have to travel, and this year that would involve going to Siberia, Mongolia, or China.

Rather than bore you with statistics about eclipses, or try to explain the geometry, I'll tell you my total eclipse story. It's a tale full of adventure, discovery, loss, love, and supernatural creatures. Okay, that's a lie. It's kinda boring. But it's true, and it's my story, so I'm sticking to it.

On August 11, 1999, a total eclipse of the sun was visible across Europe, including several major cities. I had lived in Munich, Germany in 1997, and Munich was in the path of the eclipse, so I figured that I would use the eclipse as an excuse to go and visit friends. Besides, total solar eclipses are supposed to be spectacular, and worth the cost of travel.

When I arrived in Munich a few days prior to the eclipse, telescope in tow, my plan was to go to the gardens of Castle Oberschleissheim, just outside of Munich, and hopefully away from most of the crowds that would fill the streets to try and see the eclipse. But the weather forecast was bad, with the news suggesting that one travel as far east or as far west as possible to have the best chance of seeing the eclipse.

I wanted to go east, into Hungary, but the dear friend I was staying with didn't want to go to Hungary, as it involved overnight train trips each direction, and neither of us spoke Hungarian. I was willing to risk it, but was not persuasive enough. So, we headed west to the city of Saarbrucken, which is on the border of Germany and France. The train was crowded, and I had my telescope in tow, which upset people, because it took up "too much" space (but, really, it is a small, but well-built, telescope)

For whatever reason, Saarbrucken and the French town of Forbach sent us eclipse watchers to a hill right on the border (I don't remember if the hill was officially in France or in Germany, but I know we crossed the border at least once). We rode buses from the train station to a walking trail that lead up to the hill. The German government had done a great job of explaining the dangers of looking at the sun without proper eye protection (even when the sun is 99% eclipsed, it will still permanently damage your eyes, even though it doesn't hurt to look at the sun). So numerous people told me that I shouldn't use my telescope. I had a very expensive and completely safe solar filter for the telescope, so we were okay using it. But one man in particular became almost belligerent, and I blurted out "Ich bin Astronom; ich weiss, was ich tue." (I'm an astronomer; I know what I'm doing.) Not quite as elegant as Bill Murray's line from Ghostbusters, "Back off man, I'm a scientist." But it had the same effect, and we were left alone.

On the hill outside Saarbrucken, the weather was okay. There were a few clouds, but the sun was out. I set up the telescope, and the eclipse began right on schedule! I hooked up a camera that I'd borrowed from my uncle to my telescope, and I took pictures (like the one above). All was fine until the sun was about 2/3 eclipsed. Then the thunderstorm came.

The sky clouded over, lightning danced around, and we were huddling under trees on top of a hill (dumb!!). I left my telescope set up, but my friend and I took turns holding the umbrella over it to keep it dry. And the rain poured down. The rain finally stopped a few minutes before the sun was to be totally eclipsed, but the sky was still overcast.

Right when the moon was to have totally covered the sun, the sky grew fairly (but not completely) dark in a period of just a few seconds, like someone had turned a dimmer switch down on an electric light. 129 seconds later, the lights came back up. It was still cloudy. We'd missed it.

Still, a few champagne corks popped, and the several hundred of us on the hill top started the long, wet slog back to town. We were soaked. But my telescope was dry, and I had some good pictures of the partial phases of the eclipse. We crammed onto a train and rode back to Munich.

Once back, we learned that Munich had also been cloudy, except during totality, which is the spectacular phase of the eclipse. So people in Munich got to see the best part of the show. And it had been even clearer up at Oberschleissheim, where I'd planned to be. So, if we'd stayed put, we would have seen most of the eclipse. AND, in Hungary, it was perfectly clear for the entire eclipse. Doh!

Still, I had a nice visit with friends, and I stoically accepted the weather. I was luckier than two of my friends who'd seen the eclipse in Turkey, but were then caught in the aftermath of the tragic Izmit earthquake just one week later. (My friends were lucky to have been out of the quake zone, but their return was complicated by the temblor.)

Someday I will catch a total solar eclipse. And, after that, I'll probably catch many more. I've been told that, once you've seen totality, you have to keep going back, even if it means taking a yak to the middle of the Altai Mountains.

For those of you in the United States who don't want to travel to exotic locations, you have to wait another 9 years for a total eclipse. The continental U.S. has been unlucky in eclipses; the last total eclipse in the lower 48 was in 1979, and the next one won't be until August 21, 2017. That eclipse will be spectacular for us Yanks, as it cuts a path clear across the country, from Oregon through South Carolina.

If you'd like to read more about both solar and lunar eclipses and see when and where future eclipses will be visible, check out NASA's Eclipse website.

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