The Sun in partial eclipse on 2/26/98,
photographed through optical mylar.
Photo by Susan Carroll.

How to Safely View A Solar Eclipse

A solar eclipse is probably the most spectacular celestial event that a person can experience. On February 26, the sun will undergo a total eclipse, visible from areas in the Pacific and in the Caribbean. Here in Florida, we are not in the path of totality, or the area in which the sun will be totally covered by the moon. But we will be able to see a very nice partial eclipse, in which the moon covers a large portion of the sun.

Viewing a solar eclipse can be a thrilling experience, but every time one occurs, people suffer severe and often permanent eye damage, because they do not use safe observing techniques. So here are some ways that you can view this week’s eclipse safely.

Never look directly at the sun with the naked eye! Even sunglasses will not block out damaging radiation. To view a solar eclipse safely, there are two basic, and easy methods, that can be used.

The first is called solar projection. There are several easy ways to accomplish this. Perhaps the easiest is to dig in your closet and find a shoe box, preferably one that is made out of light colored, or white, cardboard. Cut a small hole in one end (short side) of the shoe box. Cover this with a piece of aluminum foil, and then pierce a small hole in the foil using a small nail or straight pin. Point this end of the shoe box toward the sun. The sun’s image will be projected on the inside of the other end of the shoe box. You will be able to watch the sun’s disc as it is slowly covered by the moon.

You can make a larger version of this same projection system by using a large piece of cardboard, say 12 x 18, with a small hole cut in the center. Cover this hole with aluminum foil and pierce a small hole in it. Hold this so that it is front of the sun and project the image onto a large white piece of poster board set on an easel. This way several people can watch the spectacle at once.

The other basic method is to use some type of safe solar filter to view the eclipse directly. Two layers of fully exposed and developed black-and-white film can be safely used to view the sun. If you don’t have anything like this at home, you might wish to check with a local camera store; sometimes they have fully exposed black-and-white film that can be had for a nominal fee, or sometimes free of charge. Do not use black-and-white film that has images; too much dangerous radiation can be transmitted through the areas that have the images. Another safe type of filter to use are welder’s filters of shades 12 through 14. These are popular and safe, and are easily obtained at welding-supply stores. Aluminized mylar filters are also effective and safe, but I would avoid the aluminized mylar that is used in packaging of food products or collector cards because of the inconsistent quality. Although the packaging of PopTarts performs surprisingly well, I would rate this as only marginally safe.

If you are going to use optical aids to view the eclipse, such as binoculars, or a telescope, make sure that you have them fitted with solar filters designed for this purpose. Often local camera stores have these available, but be sure to tell the staff at the store what you intend to do so that they can equip you with the correct filters for these instruments. Many of the less expensive solar filters are made of aluminized mylar. If you purchase a filter of this type, test it out on a bright light bulb first and check for pinholes in the mylar. If there are any, they can easily be fixed by covering the hole using an indelible black marker. This will not result in any appreciable loss of light from the eclipse.

Unsafe filters include black-processed color film, non-silver bearing, or chromogenic black-and-white film, photographic neutral-density filters and polarizing filters. Although these materials have very low visible-light transmittance levels, they transmit an unacceptably high level of near-infrared radiation, which can cause permanent damage to the human eye.

Remember - solar eclipses are a rare and spectacular event that don’t come along very often. But observing these safety tips will make for a rewarding experience and avoid damage to your eye.

If you have access to Internet, you can view a live eclipse broadcast at http://www.solar-eclipse.org/ - and there will probably be additional sites that will broadcast it live as well. To find these other sites, check the SKY Online Eclipse Page at http://www.skypub.com/eclipse/eclipse.html; this page will direct you to other sites that are wired for eclipse watching.

The Sun in partial eclipse 2/26/98,
photographed through a Thousand Oaks Type II glass filter.
Photo by Susan Carroll.