<p><strong>Shown in a composite picture, Earth's shadow slowly "bites" into a full moon over Switzerland during a total lunar eclipse three years ago. <br></strong></p><p><strong>Stargazers in North America and elsewhere will be treated to a similar sight late tonight, when a lunar eclipse coincides with the <a id="i4j6" title="winter solstice" href="http://news.nationalgeographic.com/news/2009/12/091221-winter-solstice-2009-first-day-winter-shortest-day-year.html">winter solstice</a> for the first time since 1638.</strong></p><p>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.</p><p>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.</p><p>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.</p>