Lunar eclipse to treat skywatchers tonight |

Lunar eclipse to treat skywatchers tonight

SUMMIT COUNTY – If the clouds hold off, mountain residents can expect quite a show tonight – the first total lunar eclipse of the year.

The sun is expected to set tonight at 8:12 p.m. (unless, of course, you live in Frisco in the shadow of Mount Royal), and the moon will rise shortly thereafter. The eclipse, which happens as the moon passes through Earth’s shadow, should already be in progress and will last about three hours.

The celestial show is special because it’s the first lunar eclipse visible from North America in more than three years. The next visible lunar eclipse will occur later this year, in November.

Colorado Mountain College astronomy professor Sig Kutter explained a lunar eclipse does not come on suddenly. “It starts very gradually, almost imperceptibly,” he said.

Sunlight on the Earth creates two conical shadow zones. One, called the umbra, is the cone directly behind the Earth and is almost completely dark. The penumbra, the cones outside the umbra, are shadow zones but not as dark as the umbra. For an example, shine a flashlight or a bare light bulb at a tennis ball or other spherical object and examine the shadows cast on the wall or floor.

The eclipse begins as the moon starts to pass into the penumbra. In a partial eclipse, the moon will pass only through the penumbra. Total eclipses occur only when the moon is full and it passes through the umbra.

The moon will slowly darken. Once the moon enters the umbra, it will be almost completely dark. This phase of an eclipse is called the totality. The totality of tonight’s eclipse is expected to last 53 minutes, Kutter said, from 9:14 p.m. to 10:07 p.m.

But you’ll still be able to see the moon, Kutter said. Even though the moon is in the darkest shadow of Earth, sunlight gets bent in the outer atmosphere of the planet and refracted to the moon. The refraction scatters most of the shorter, bluer wavelengths of sunlight. Red and orange light gets through, much like during a sunset, Kutter said.

“This filtering can give the eclipsed moon a dramatically colored appearance, from bright orange to blood red to dark brown, and, rarely, very dark gray,” Kutter said. “If you stood on the moon and looked toward Earth, the sun would be blocked, but you’d see a continuous, orangy-red right, a continuous sunset, all around the Earth.”

After totality, the moon will pass into the penumbra on the other side and become brighter with each passing moment. The eclipse will end about 11:18 p.m.

Unlike solar eclipses, lunar eclipses are safe to view with the naked eye. Binoculars or a telescope will reveal more detail in the moon.

For tips on photographing the eclipse, log on to

Reid Williams can be reached at (970) 668-3998, ext. 237, or

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