Total Lunar Eclipse
Shown in a composite picture, Earth's shadow slowly "bites" into a full moon over Switzerland during a total lunar eclipse three years ago.
Stargazers in North America and elsewhere will be treated to a similar sight late tonight, when a lunar eclipse coincides with the winter solstice for the first time since 1638.
Around 1 a.m. ET Tuesday, you may notice a ghostly shading of the moon, marking the arrival of Earth's faint outer shadow, or penumbra.
Shortly after 1:33 a.m. ET, begin looking for the first signs of a dim "bite" (as shown at left in the picture above)—Earth's shadow—advancing across the moon from the left.
The total eclipse, or totality—when the entire moon is dimmed, but not completely darkened, by Earth's shadow—begins tonight at 2:41 a.m. ET and will last a little over 70 minutes.