SKY & TELESCOPE photographer Rick Fienberg took this picture of a 1996 lunar eclipse.

On the night and early morning of Jan. 20-21, Americans and Western Europeans will be able to witness the first total lunar eclipse in more than two years.

A total lunar eclipse occurs when the sun, earth, and moon form a straight line in space and the moon passes through the earth's shadow. This can happen only when the moon is full, as it is on the night of Jan. 20-21. Unlike a solar eclipse, which requires special equipment to observe safely because of the sun's radiation, a lunar eclipse can be safely viewed with unaided eyes. However, binoculars or a small telescope can enhance the view dramatically.

As the moon moves into the earth's outer shadow, or penumbra, it will begin to fade slightly, but the effect is almost imperceptible. Once the moon encounters the dark inner shadow, or umbra, the change is dramatic. The part of the moon in the umbra should appear dark, while the part still in the penumbra will still be light. During totality, when the moon is fully within the umbra, it will remain very dimly visible as sunlight scattered by earth's atmosphere paints the lunar surface with a warm, reddish-orange glow. As the moon emerges from the earth's shadow, it will regain its brightness. From start to finish, the eclipse takes about four and a half hours.

Total Lunar Eclipse of Jan. 20-21, 2000, in the USA