Rare Solar Eclipse on Christmas

The moon’s shadow will appear to take a Christmas Day bite out of the sun Monday, giving Americans a rare look at a partial solar eclipse.

The partial eclipse will be visible over most of the continental U.S., with the best view in the Northeast, where about half of the sun will be obscured. People in Hawaii and Alaska won’t see the eclipse.

A solar eclipse occurs when the moon is positioned between the sun and the Earth. This casts a lunar shadow on the Earth’s surface and obscures the sun.

Only part of the sun’s sphere will be covered on Christmas; no place on Earth will see a total eclipse. The sun will be most obscured when viewed from Baffin Island, Canada, where 72% of the sun will be covered.

During a total eclipse, the moon’s dark inner shadow, called the umbra, strikes the Earth. During a partial eclipse, only the more faint outer shadow, called the penumbra, strikes the Earth. The Christmas Day partial eclipse results when only the penumbra sweeps across North America.

A full solar eclipse can cause brief, localized darkness, but there is expected to be only a slight dimming of sunlight Monday at maximum eclipse points in the Northeast.

In Los Angeles, the partial eclipse begins at 7:37 a.m., reaches its maximum of 7% at 8:23 a.m. and is over 50 minutes later. Farther north, more of the sun is covered. In Seattle, 25% will be obscured at 8:29 a.m.

In New York City, the eclipse begins at 11:09 a.m. EST, reaches its maximum at 12:47 p.m., and ends at 2:21 p.m. About 44% of the sun will be obscured and daylight intensity will dip slightly.

The American Optometric Assn. warns sky-watchers to not look directly at the eclipse.

“Looking at a solar eclipse without proper protection can result in serious eye damage,” the association warns in a statement. To view the event, experts recommend special equipment, such as a welder’s lens, a pinhole projector or other indirect viewing equipment.

A special eclipse lens, called No. 14 welder’s glass, can be purchased at welding supply stores. Some science equipment stores offer glasses for safe eclipse viewing.

Sky & Telescope says a homemade device, called a pinhole projector, is one of the simplest ways to view the eclipse. Take two index cards and poke a round hole in one. Hold the punctured card with the flat side toward the sun. Put the other card several feet behind and below the first card. A small, inverted image of the sun will project onto the second card.

The optometric association warns that viewers should not use sunglasses, smoked glass, polarizing filters or photo or X-ray film to look at the sun.