View the May 20, 2012 Partial Solar Eclipse

Eclipse Stream from Allen Telescope Array

Live video by Ustream

eclipse

If it’s clear on May 20, you’ll be able to see about 84% of the Sun covered by the Moon from the San Francisco Bay Area.  The eclipse begins at 5:16 pm, reaches the maximum coverage at 6:33 pm, and ends at 7:40 pm. As the eclipse goes on, the Sun will be lower and lower in the northwest sky, so you’ll need to find a viewing place not blocked by hills or houses.

An eclipse of the Sun happens when the Moon gets between the Sun and the Earth and covers up some or all of the Sun. Sometimes the Moon covers up all of the Sun (a total eclipse), but more often only part of the Sun is covered (a partial eclipse.)

This particular eclipse will not be total anywhere on Earth – even where the viewing is best, the Moon will still leave a ring of light around the edge of the Sun uncovered (this is called an annular eclipse.) The Moon is close to the furthest point from the Earth in its orbit, so it’s smaller in our sky and can’t fully cover the Sun.

In the U.S., different cities in the western parts of the country will see different amounts of coverage, but in no case is the eclipse enough to make the day look darker. Thus most people will not even notice that the eclipse is going on.

Looking directly at the Sun is VERY DANGEROUS to unprotected eyes, so it is best to go to an eclipse viewing site where they have safe viewing tools or to prepare a way to project an image of the Sun.

The best way to see the eclipse is to project an image of the Sun (and not to look at the Sun directly.) One easy way is to make a pinhole projector: Take two pieces of cardboard or thick paper. Put a pinhole in one (taking care to make a clean hole). Then stand with your back to the Sun, and let the Sun’s light fall through the hole and onto the other sheet. You’ll get a small but distinct image of the Sun. (A way to get a sharper pinhole is to cut a square out of the middle of one cardboard, tape a sheet of aluminum foil over the hole and put the pinhole in the foil instead of paper.)

To look at the Sun directly, you need a good filter that can cut out not just light but also ultraviolet and infrared waves. Sunglasses, exposed film, and smoked glass are NOT OK! If you have access to welder’s supplies (and not many people do), #14 arc-welder’s glass is an excellent filter (but it has to be #14 and not lower numbers). Or you can use special black or aluminized polymer filters/glasses available at many telescope stores or planetaria; but make sure you get them from a reliable source.

You should definitely NOT look at the Sun through unfiltered binoculars or a telescope, because they concentrate the rays and make looking at the Sun MORE dangerous, not less. Only use such instruments if you have a reliable solar filter and know how to use it!

Throughout the Bay Area, astronomy clubs and organizations will have eclipse parties for the public. Check out the website of the Astronomical Society of the Pacific (www.astrosociety.org) for a listing. And for a national listing of astronomy clubs that like working with the public, see: http://nightsky.jpl.nasa.gov/club-map.cfm

Find locations to view the eclipse in the San Francisco Bay area.

Text by Andrew Fraknoi, SETI Institute Trustee