Reading aloud What happens and what does one see? Tips for observing and photographing the Black Sun. A total solar eclipse is not just a special geometric constellation of the sun, moon and earth. The poet Adalbert Stifter called it a heartwarming "experience - in his description of the eclipse of July 8, 1842 in Vienna:

"The tension rose to the highest level - one last glance I did into the star tube: as narrow as scratched into the dark with the edge of a penknife stood only the glowing sun sickle, extinguished every moment. And like the last spark of a wilting wick, the last spark of the sun also melted away. Covering was now disc to disc - and this moment it was actually, which seemed truly heartwarming. Dead silence, it was the moment when God spoke, and the people listened. "

On the 11th of August of this year 1999 skeptics will have to admit that Stifter did not exaggerate.

The first partial phase of darkness begins with the first contact. In the course of 1 hour and 20 minutes, the sun becomes smaller and smaller until only a small sickle remains on the left side. During this time, one is easily tempted to watch the approach of the great moment with a sun-directed gaze - a dangerous undertaking, because even if only a narrow sun sickle is left, the sun shines here with undiminished brightness and could cause severe retinal damage, In the waiting rooms of the ophthalmologists after eclipses there is often bustle. One should by no means look with unprotected eyes in the sun, certainly not with the binoculars. display

In many cases goggles are offered with a metallized film, through which one can look with impunity. Although there are also simpler means, for example, two glued black slides - as they always occur after the development of a slide film at the beginning or end - but they do not provide safe protection, you should look so only briefly in the sun. For the rest, a quick glance is enough to see how far the moon has now moved in front of the sun.

Completely inadequate is a normal pair of sunglasses. It dampens the light in a sunlit landscape, for the sun itself it would have to be many thousand times darker.

You must also not look with goggles to the sun through a binoculars: The concentrated solar heat could burn a hole in the foil, and at the same time the clenched sunshine hits your retina.

The moon is not a smooth globe, it has lowlands and mountains, valleys and mountain peaks. When the smooth edge of the sun sinks behind this bumpy lunar edge, the sun finally flashes out of some lunar valleys. The last rays of sun are like pearls on a chain strung around a piece of the moon: only a short moment the "string of pearls" lights up - a charming sight that should not be missed. A split second later, the last sun bead on the left side of the moon goes out. At the same time it is dark. Now no eye protection is needed anymore - with him you would not see anything of the magnificent view offered by the sky, which you can admire with the naked eye and even with the binoculars: Where just the sun shone from the sky, stands a pitch black Slice, surrounded by the shimmering silver halo of the corona. At its inner edge you can see the red flames of the prominences: Here gigantic hydrogen fountains shoot up from the sun.

The total eclipse takes in the center of the strip near Stuttgart 2 minutes 17 seconds, in Munich 2 minutes 19 seconds, in Salzburg 2 minutes 21 seconds. As the distance from the centerline increases, the duration of the totality becomes shorter. Now the first sunbeam flashes on the right side of the moon - just about where the moon touched the sun for the first time on the first contact. At the same moment it will be light again on the earth. The second partial phase has begun, which lasts about 1 hour and 21 minutes. The moon is revealing more and more of the sun, until - the 4th contact - the last dent on the left side of the solar disc disappears. Moon and sun are now separated again: the eclipse is over.

Not only in the sky, but also on earth are amazing phenomena to observe. As the moon gradually moves in front of the sun, it becomes noticeably cooler and the temperature drops almost evenly by about six degrees. Due to the temperature difference, it is also windy.

How dark it gets is hard to predict. In any case, the darkness should be enough to see at least the brighter stars of the sky, for example, Arcturus, the main star of the "Bear Drivers" boat, and Capella, the brightest star in the wagoner. In direct sunlight you will definitely find the bright Venus left below the Sun and the Mercury a bit further to the right above it. Venus is usually visible long before the totality as the first "star" in the ever darkening sky.

Things get exciting when the sun melts away just before the second contact. Now, in the final seconds before the total darkness, you should also look to the west: With more than double the speed of sound, the shadow comes rasturely - like a huge dark storm wall, from which one threatens to be overrun. Many have already missed the pearl cord. It's terribly exciting, maybe you're just staring up at the sky, forgetting the whole world around you, to see the corona glowing. Now the big time has come for maybe the most precious photos you make in your life. No one in Karlsruhe, Stuttgarter, Munich or Salzburg will experience such a fascinatingly sinister time as the one on 11th August 1999.

Something similar to the beginning of total eclipse occurs at its end: on the right side, the sun suddenly appears again in the form of a first flash of light at the deepest incision on the edge of the moon. Immediately thereafter, a few flashes of light join in addition. But after all experience now hardly anyone thinks about taking pictures. Almost everyone is filled with the wonderful experience, and often a celebration celebrates the big event.

Wolfram Knapp

science.de

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