Not every full moon is the same. Because the moon orbits in an elliptical path around the earth, the distance between the Earth and moon can vary considerably from one week to the next.
At apogee (the moon's farthest point from Earth), it is 50,000 km farther from Earth than it is when the moon is at perigee (the closest point to earth). And that change in distance means that the full moons that we see each month vary in size, depending on whether the time of full moon is closer to apogee, perigee, or some point in between.
Because the lunar perigee occurs Friday, at the same time that the moon reaches its full phase, we will see the biggest, brightest full moon of 2008. In fact, tonight, we will see the biggest full moon since 1993. The moon will be 14 percent larger and 30 percent brighter than a full moon that occurs near apogee.
The sky will be mostly clear and the humidity low, making for ideal viewing conditions. So bundle up, and check out the full moon tonight.