Lunar eclipse to turn the sky red

Stargazers will likely tonight see the moon turn an eery shade of red. It's a total lunar eclipse that will be visible to everyone in North and Central America, weather permitting.

During a lunar eclipse, the sun, earth and moon are all perfectly aligned with the earth in the middle. When the moon passes behind the earth, the sun's rays are blocked from striking the moon. This can only occur when the moon is full.

According to NASA, Earth's atmosphere bends sunlight into earth's shadow and onto the moon. The sunlight is reddened as it travels through earth's dusty atmosphere, and so the moon looks red. Sunsets on Earth look red for the same reason.

It's the first time in almost 500 years that a lunar eclipse has coincided with the winter solstice — the shortest day of the year — December 21.

And there it's a once-in-a-lifetime chance to see a selenelion, which occurs when the sun and the eclipsed moon can be seen at the same time. This is also known as a horizontal eclipse, because both sun and moon appear above the horizon at nearly opposite points in the sky.

The night will begin with a bright full moon, and by 1:33 a.m., the moon will begin to darken on the left side. The shadow will spread until it nearly covers the moon. The eclipse will last for about an hour and a half and is safe to observe with the naked eye.

Check out Space.com for a handy guide tot he 12 stages of the eclipse and tips on how to view it.