Last month the full moon was extra big, not just in perspective — it was documented: the biggest full moon of 2008, a perigee moon, 14 percent wider and 30 percent brighter than before. Get ready for a repeat performance this Saturday night, January 10th, another perigee moon is coming. It's the biggest full moon of 2009, almost identical to the one that impressed onlookers in December 2008.

The perigee full moon of December 2008. "The moon was very bright and BIG! Just watching it with my telescope was exciting enough, but I had to take this picture for the records," says photographer Ron Hodges of Midland, Texas.

Johannes Kepler explained the phenomenon 400 years ago. The moon's orbit around Earth is not a circle; it is an ellipse, with one side 50,000 km closer to Earth than the other. Astronomers call the point of closest approach "perigee," and that is where the Moon will be this weekend. Perigee full moons come along once or twice a year. 2008 ended with one and now 2009 is beginning with another. It's the best kind of déjà vu for people who love the magic of a moonlit landscape.

January is a snowy month in the northern hemisphere, and the combination of snow and perigee moonlight is simply amazing. When the moon soars overhead at midnight, the white terrain springs to life with a reflected glow that banishes night, yet is not the same as day. You can read a newspaper, ride a bike, write a letter, and at the same time count the stars overhead. It is an otherworldly experience that really must be sampled first hand. Left: The perigee full of December 2008. "A cold wind was blowing as the moon set over a neighbor's farm," says photographer Eric Ingmundson of Sparta, Wisconsin. "Next time (January 10th) I plan to use a tripod."

Another special moment happens when the perigee moon is near the horizon. That is when illusion mixes with reality to produce a truly stunning view. For reasons not fully understood by astronomers or psychologists, low-hanging moons look unnaturally large when they beam through trees, buildings and other foreground objects. Even at perigee, the Moon is 360,000 km away, yet the distant beauty beckons to poets, stargazers and NASA with equal force.