Keen sky-watchers may notice that October's full moon, known traditionally as the Hunter's Moon, will lose just a bit of silvery luster tonight as part of its southern limb gradually dims. What is happening is that Earth's outer, pale shadow is falling on the outer edge of the lunar disk.

The celestial phenomenon, known officially as a penumbral lunar eclipse, may be a bit tricky to catch in the sky with the eye, however, since the shading effect will be quite subtle.

Armchair astronomers can watch a live feed of the eclipse, thanks to SLOOH. The Internet-based space-tracking service is broadcasting the eclipse with its robotic telescopes on the Canary Islands (map) starting at 4:30 p.m. EDT (23:30 UT).

"Penumbral