A note on observing a solar eclipse

Observing a solar eclipse can be carried out on many levels. You can use the naked eye, binoculars, a telescope (a small 2- to 3-inch telescope will suffice), or video camera. Whatever you use, though, an absolute must is proper protection for your eyes and instruments. As mentioned above, it is perfectly safe to look upon a fully eclipsed Sun, but never at one that is partially or mostly eclipsed. For details on solar filters for optical systems and the projection method of observing, see 'The skywatcher's Sun' in this book.

The simplest method of observing a solar eclipse is the pinhole camera method. You simply punch a 1-mm hole into a small card and allow the sunlight to stream through the hole onto a second card held 30 centimeters or so away. Sometimes, though, it can be difficult to see the relatively small, dim disk of the Sun in daylight. A variation of this pinhole camera method that alleviates glare is to punch a clean 1-mm hole in one end of a large cardboard box through which the sun's light will enter. On the opposite end, attach a piece of white paper to act as a screen. Holding the box over your head, you stand with your back to the Sun, orienting the hole so the sunlight streams through, and view the projected image on the paper. This method provides both shade and a personal viewing environment, if you don't mind being seen with a large box over your head.

For direct observation and photography, mylar or aluminized glass filters should be used during the partial phases. Mylar 'eclipse glasses,' which you place over your eyes, allow you to look directly at the Sun without fear of injury. Eclipse glasses are available from a number of telescope dealers. You can also use number 14 rectangular arc welder's glass for direct observation. Under no circumstances should you use multiple layers of sunglasses, black and white photographic negatives, or an improper grade of arc welder's glass to look at the Sun.

In the latter stages of partiality, there is another phenomenon worth looking for. Note the mottled appearance of light and shadow under leafy trees. You'll see that the dappling light consists of hundreds of crescent-shaped images of the Sun. The leaves in the tree act like a multi-pinhole camera. A similar effect can be produced by interlacing your fingers and allowing sunlight to pass through the small openings.

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