Ask A Scientist© Astronomy Archive

Author:      vicki s maiden
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 10,1994?  Is
there a safe way to view it?  

Response #:  1 of 1
Author:      rcwinther
There are good write ups about this in the May 1994 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 around the Moon which can cause damage if it is stared at unpro-
tected.  (Needless to day, you should not view this eclipse through binocu-
lars or a telescope either!) The magazines mentioned above describe eye
protection that is adequate for safety; they emphasize 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 shoe box, 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 the 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 page 94 of the May 1994 issue of Astronomy for a more complicated 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, because 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 have inadvertently made the hole too
large.) In any case, the image will be small - less than a centimeter in
diameter (the longer the box, the larger but dimmer the image will be).  But
it is the shape of the image that is interesting; the size should not really
matter, as long as it is large enough to see.