There aren’t many reasons to wake up at a quarter of 5 a.m., but tomorrow’s celestial phenomenon—a total lunar eclipse—may be one of them. The second of 2007, tomorrow’s eclipse will be but a fleeting treat for Washington and the rest of the eastern U.S. According to the U.S. Naval Observatory’s friendly and helpful public affairs Officer, Geoff Chester, Washington will be lucky enough to see the Moon slip into the Earth’s umbral shadow a little more than a half hour before it sets in the pre-dawn hours.

At 4:51 a.m. tomorrow morning, the Moon’s eastern limb (its left edge) will begin to enter the Earth’s shadow. About ten or 20 minutes before this, the Moon will be in the Earth’s penumbra. Chester says the Moon will take on a “subtle gray shade” during this time, but you’ll have to look close to see it, as the Earth’s penumbra is very diffuse. Between 4:51 and 5:52 a.m. is the period of the Moon’s partial eclipse, and at 5:52, totality begins. The Moon will start slipping below the horizon as this happens, and will be in total eclipse until moonset at 6:27 a.m.

Photo of March 2007’s lunar eclipse from philliefan_99.