Is A Solar Eclipse Safe?
Name: vicki s maiden
Date: 1993 - 1999
I am writing from Munhall School in St. Charles, Il. My principal
needs to know if it is safe for the students to view the eclipse on May 10? Is
there a safe way to view it. We need to know ASAP. Thank you.
There are good writeups about this in the May issue of both Astronomy
and Sky & Telescope magazines. It is NOT safe to look directly at this eclipse;
it is an annular (not a total) eclipse, which means that even at maximum
coverage of the sun by the moon, there is a ring (or near-ring) of bright sun ar ound the moon which can
cause damage if it is stared at unprotected. (Needless to day, you should not
view this eclipse through binoculars or a telescope either!) The magazines
mentioned above describe eye protection that is adequate for safety; they emphas ize that sunglasses,
smoked glass, crossed polarized lenses and other similar "protection" are NOT
adequate. A safe way to view the eclipse is to use the "pinhole camera"
principle to project an image of the eclipse and observe this image. This may be done using something as
simple as a large piece of thin opaque cardboard having a small hole; the image
will be within the shadow of the cardboard. A bit
more sophisticated setup: use a long box such as a shoebox, with a removable
lid. Punch a small hole in one end, and glue a piece of white paper on the
inside of the box covering the side opposite the hole. To view, turn the box
upside down, hold it over your head, and "point" the end with the hole toward th e sun. the image will be
projected onto the white paper. A word about the hole - the smaller the hole,
the sharper but dimmer will be the image. A larger hole will produce a brighter
but fuzzier image. (See p. 94 of the May issue of Astronomy for a more complicat ed box arrangement
that makes for improved viewing.) A good compromise is a hole about 2 mm in
diameter, but you should experiment for yourself. Some writers suggest cutting a
piece out of the "hole" end of the box and covering this with a piece of foil, b ecause it is very
thin but opaque and allows a very small pinhole to be made. (This is also a good
way to salvage your box and make a new hole if you've inadvertently made the
hole too large.) In any case, the image will be small - less than a centimeter i n diameter (the
longer the box, the larger but dimmer the image will be).
But it's the shape of the image that is interesting; the size shouldn't really
matter, as long as it's large enough to see. Good luck!
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Update: June 2012