crescent sun!
by Morgan Davis

San Diego homeschoolers had the best opportunity in the country to watch the moon pass in front of the sun on June 10, 2002. At 6:23pm about three quarters of the sun were covered at the peak of the eclipse. We decided to take a picture of it.

To get the shot shown at right, we held special solar viewing glasses in front of the lens of our digital camera and took the picture. Without it, the image would have been over-exposed (completely white). To keep the camera from automatically focusing on the glasses in front of the lens, we had to put it on manual and set the focal point to infinity.

A digital camera's "film" is called a CCD (or charged coupled device). It is a sensitive electronic chip tuned for normal light levels, much like the retina in your eyes. But unlike your eyes, too much light won't damage the camera, though it will wash out the image. The dark filter in the solar viewing glasses let in the right amount of light for the camera to capture this rare event.

These glasses are made of a special filter material that blocks the sun's light by a factor of several hundred thousand. Wearing them makes it possible for you to safely view the sun for brief periods of time without damage from dangerous ultraviolet and infrared radiation.

Never look directly at the sun without protective eyewear made specifically for solar viewing. Sunglasses, 3-D glasses, or photographic filters do not protect you from permanently damaging your eyes. Good filters include commercially available Mylar filters and metal-on-glass filters or a #14 arc-welder's glass. (See the link below to see how to make a simple pinhole projector for viewing the sun.)

We received our solar viewing glasses in an issue of Astronomy magazine. You can find them for a couple of dollars in science centers and stores that sell science equipment. Unfortunately, there is no hurry to get a pair unless you plan to travel to other parts of the world. The next partial eclipse for San Diegans will be in 2012, and the next total eclipse will be in 2017.


Want to learn more about eclipses? These web sites shed more light on this fascinating astronomical phenomenon.

Moonshadow: What Causes a Solar Eclipse?

MrEclipse.com

Solar Eclipses (Newton's Apple)

How to Make a Simple Pinhole Projector

Annular Solar Eclipse

Upcoming and Recent Eclipses