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Dec. 4, 2000

Partial Solar Eclipse To Occur On Christmas Day

By Dr. Patrick Seward, RSU Associate Professor of Mathematics and Science

Residents of Green Country may witness a most beautiful and interesting natural phenomenon – a partial solar eclipse – at 9:36 a.m. on Monday, Dec. 25.

On Christmas Day, the moon will drift across the upper left edge of the Sun, casting its sharp, round shadow across the Sun's surface. Here in northeast Oklahoma and southeast Kansas, fully one third of the Sun's disk will be covered, drenching our already frigid winter landscape in a dull amber glow. During the eclipse we will receive approximately the same amount of light an astronaut might experience on the surface of Mars on a bright, clear, summer Martian day.

The Christmas eclipse is exciting because this particular type of eclipse is not a common event in North America. Lunar and solar eclipses of this type occur on our portion of the Earth about every 54.1 years; the last event, every similar to our Christmas eclipse, occurred on November 26, 1946.

Regardless of how you may plan to view the eclipse, it is absolutely crucial that you do so safely. Unfiltered, radiation from the Sun can permanently damage your eyes. The partially-shadowed disk of the Sun during an eclipse is just as dangerous as on a bright, sunny day. Do not attempt even a quick peek at the eclipse without appropriate eye protection or by projecting the Sun's image onto a piece of cardboard.

The Sun is low this time of year and so we may safely view the eclipse by several methods. Locate a room on the south side of your house. Darken it by drawing the curtains or pulling down the shades. Make sure there is a tiny crack somewhere in the window coverings so that a tiny bit sunlight is allowed to project onto the far wall or floor. You will be able to see the small piece of the sun missing in this tiny image. Do not be tempted to look back out through the crack directly at the Sun. Again, severe damage to your eyes could result. You may dramatically improve the quality of the image beaming through the crack in your window coverings by punching a tiny hole in a piece of cardboard, passing the sunlight through that hole, and projecting the image onto another flat, white piece of cardboard. Make the hole small, generally no more than a tenth of an inch or so. The hole's edges should be sharp and cleanly cut as possible.

If you would like to view the eclipse directly, you have several choices: you may use a welder's glass with a shade value of 13 or 14. This glass can be purchased at a welder's supply store very cheaply. Do not buy glass of a smaller value than 13 or 14, your eyes could be damaged by the intense radiation. Cover both eyes with the glass when viewing. It should be wide enough. Another option is to purchase a special filter designed specifically for viewing the Sun. These solar filters may be very dark, specialized glasses or simply an extremely dark piece of film designed for viewing solar phenomena.

Following are several sources for safe solar filters: