Eye on the Sky: Total Lunar Eclipse Is Tonight

Tonight, all of North America will get the opportunity to see the Earth's shadow pass in front of the moon — a more than just a once-in-a-lifetime opportunity, since for the first time in nearly four centuries, the total eclipse will coincide with the Winter Solstice.

The event is expected to last three hours and 28 minutes tonight, starting at 12:33 a.m.

Although it's the second lunar eclipse of 2010, it is the first total lunar eclipse since Feb. 20, 2008. And, astonishingly, the last total lunar eclipse that occurred simultaneously with Winter Solstice happened in the year 1638.

The last lunar eclipse of 2010 is especially well placed for observers throughout North America, according to NASA's website for the Dec. 21 eclipse. A lunar eclipse happens when the moon passes behind the Earth and is shielded from the sun's rays. Because the sun, moon and Earth must completely align for this to occur, a lunar eclipse can only happen when the moon is full.

For those of you hoping to catch a glimpse of lunar history, here's a timeline for tonight's eclipse:

• 12:33 a.m. — partial eclipse begins
• 1:41 a.m. — total eclipse begins
• 2:17 a.m. — mid-eclipse
• 2:53 a.m. — total eclipse ends
• 4:01 a.m. — partial eclipse ends

Adler Planetarium in Chicago is marking the occasion tonight with a Total Eclipse Lunar Party. Skygazers can watch the eclipse with Adler astronomers – and get some help setting up their telescopes — from 11 p.m. to 4 a.m. at the planetarium, 1300 S. Lake Shore Dr. Visitors can bring their own telescopes or use one provided by Adler.

The last eclipse of 2010 happened on June 26, but was nowhere near as vivid as tonight's is expected to be, according to NASA.

The color and brightness of the totally eclipsed moon, according to NASA, is likely to be a dark eclipse because of Indonesia's Mount Merapi recent volcanic eruptions. Dark eclipses are caused by volcanic gas and dust that filter and block much of the sun's light from reaching the moon, according to the website. The total eclipse phase will be bright red and orange.

The moon will be completely concealed by the Earth — known as "totality" — for just slightly more than 72 minutes, something NASA officials say is "quite a bit longer than the last total lunar eclipse."

The next total lunar eclipse isn't expected until Dec. 10, 2011. The next total eclipse that will be visible from the Chicago area won't happen until April 15, 2014, according to Adler's website.