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This article is from the In-Depth Report It's Back! Total Solar Eclipse Hits Skies Friday

Tips for Eclipse-Watchers

How to preserve your eyesight and get great eclipse photos



Exploratorium

So that you can prepare and not miss this event on the first day of August, here are a few tips for observing the partial solar eclipse that will be visible in Germany and most of Europe. Those of you who are able and willing to travel to Russia, Mongolia or northern China can view the more than two-minute-long totality and also see the sun's corona and the moon's deepest shadow (umbra).

In Germany and Europe, those who are unaware of or uncaring about this fairly rare event will probably not even notice it. The moon's dark limb will achieve maximum partial coverage of the sun in northeastern Germany. Nevertheless, about 20 percent of the diameter of the sun will be in shadow over Berlin at around 11:32 Central European Summer Time (3:32 A.M. Eastern Standard Time); in Freiburg, in southern Germany, unfortunately, only about 6 percent.

Without a safe filter such as a special set of eclipse glasses [see image], the human eye won't even be able to make out what is happening—and to look directly into the sun without protection is to court permanent blindness! In addition, the portion of the sun's surface that is covered is so small that changes in light conditions in Berlin will be imperceptible.

The progression of the phases of the partial eclipse may be observed using a small telescope mounted on a tripod or with binoculars and a white projection screen. A white sheet of paper on cardboard makes a very serviceable screen. Any accessible lens with a focal distance of 15 to 25 millimeters can be used to project the image.

This method of observing the sun is completely safe, does not necessitate a lens filter, and it has the added advantage that the eclipse can be observed by several persons at the same time. CAUTION: If neighbors or children drop by, make sure that none of them tries to look directly through the telescope or binocular eyepiece, because this can rapidly cause irreversible eye damage.

You can take a beautiful series of photographs of the progression of the partial eclipse using the conventional methods of solar photography. Depending on your geographic location in Germany, you will need to be ready to shoot between about 10:35 and 12:35 CEST. You will need a solar filter foil from the Baader Planetarium company with a density of D=5 for visualization, which you can mount on the telescope opening with a simple cardboard mount. Then mount a mirror reflex camera to the focus of your telescope, which will require you to remove the lens and use a focal adapter.

Select as low a sensitivity as possible. The resultant exposure time should be in the range of one two-hundred-and-fiftieth to one two-thousandth of a second. Determine the precise value by using a spot meter on the noneclipsed part of the solar disk. Integrated exposure meters tend to overestimate exposure time the smaller the solar image is in relation to total image size.

The total eclipse in Asia
There is a fundamental difference between partial and total solar eclipses. Only in totality, which occurs along the narrow strip that describes the cone vertex of the deepest shadow of the moon on Earth's surface, is it dark enough to see the sun's corona in all its magnificence surrounding the dark disk of the moon. The edge of the congruent moon and sun is surrounded by reddish-pink protuberances, and this bright, colorful light show around the edge contrasts with the drastic decrease in overall sunlight just before totality.

This fascinating natural drama is such that thousands of amateur astronomers travel long distances whenever a total eclipse is on the agenda. This time, places like Novosibirsk in Russia and Xian in China are the major travel destinations for astrotourists. Unless you have already booked your trip, you will have to go on a waiting list.

You can take stunning photographs of the corona using a camera, a tele-lens with a focal length of 400 or 500 millimeters, a stable tripod, and a shutter-release cable. The best thing to do is to take an exposure series from one five-hundredth up to one second, and to overlay the images later on your computer. This will enable you to prevent the external corona from remaining dark while the internal area is overexposed and bleached out.

Shortly before totality, make sure to reset your lens on a distant object such as a mountain peak. Some mirror optics exhibit a pronounced thermal response such that during the considerably cooler totality phase the focus may no longer be where you set it in preparation for the eclipse! But the critical factor is time. Two minutes of totality seem to pass like 20 seconds. So don't try to do too much, just try to enjoy the show!

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