A guide to viewing Sunday’s partial eclipse

  • Thu May 17th, 2012 4:50pm
  • Life

By Mike Lynch

It’s been a while since we’ve had a total solar eclipse around here and, even though today’s afternoon and evening eclipse will be a partial, more than 80 percent of the sun will be covered by the moon.

The eclipse will begin a little after 4 p.m. and will end shortly before 7 p.m. With the proper precautions it should be a really great thing to see.

As it is with any eclipse you never want to stare at the sun. It’s not good for your eyes and you could easily do permanent damage in a very short time. Viewing it through binoculars or a telescope you could go permanently blind in less than a second.

If you don’t have special eclipse safety glasses the only other way to watch the moon march across the sun is the projection method. As you see in the diagram hold a piece of white cardboard with a pinhole in it over another piece of stiff white cardboard. White fiberboard works well, too.

The best and safest way to aim the piece with the pinhole at the blank card is to stand with your back to the sun and hold the pinhole piece back toward the sun. Use the shadow of the cardboard to aim it over the blank cardboard and you should be able to see the eclipse with absolutely no danger. It really works.

Another really unusual thing about this solar eclipse is that no one on Earth will see a total eclipse. In the path that stretches from western Texas to Northern California and then across the Pacific where under normal eclipse circumstances you’d see a total solar eclipse, viewers will instead see something called an annular eclipse.

The silhouetted disk of the moon runs right over the top of the sun but isn’t large enough to cover it entirely. Observers will see the dark disk of the moon surrounded by a ring of fire. So what’s going on here?

The answer is that moon has strayed away from the Earth, but only temporarily. This happens because the moon’s 27.3 day orbit around Earth is not a perfect circle but rather an ellipse. This causes the moon’s distance from us to vary during the month by about 31,000 miles.

When the moon is at its closest at lunar perigee and we have a solar eclipse, the sun is completely covered to create a total solar eclipse. When the moon is at its farthest point from the Earth at apogee during an eclipse, its apparent size is not quite large enough to completely block the sun’s disk, leaving a brilliant ring of sunlight encircling the silhouetted moon.

That’s what happening this evening in the southwestern United States. While annular eclipses are not as breathtaking as a total eclipse, they are still amazing.

We’re actually in a blessed age for solar eclipses because most of the time the moon is close enough to the Earth to give us full-strength total solar eclipses. Thousands of years from now that won’t be the case because the moon is drifting away from the Earth at the rate of about an inch and half a year. Eventually every solar eclipse we’ll be an annular eclipse.

If you ever have a chance to see a total eclipse do it. They are truly magical. The next full bore total solar eclipse in the continental United States will be in August 2017.

Mike Lynch is an astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of the book, “Washington Starwatch,” available at bookstores. Check his website, www.lynchandthestars.com.

The Everett Astronomical Society: www.everettastro.org/.

An animation of the view from Washington state.

• Watch online: The Slooh Space Camera will stream live feeds from telescopes in Japan, California, Arizona, and New Mexico, starting at 2:30 p.m. PDT. To watch, go to Slooh’s homepage.