The Show Begins at 8:43 p.m.

This Wednesday, Feb. 20, New Englanders will be treated to a total lunar eclipse - the last one until late December, 2010.

Last week's column explained some of the quirks and quiddities underlying lunar eclipses in general. Here, we provide a quick users guide to observing this particular event.

The most practical way to proceed, oddly, is at the middle: The totality peak will be at 10:30 p.m. Here, the moon will be entirely engulfed by Earth's shadow. A dark disc will sit in the southern sky at higher than 60 degrees from the eastern horizon. The black disc, previously a ruddy-hued moon, will be flanked by Saturn to the lower left and Regulus (brightest star of the Leo constellation) to the upper right.

This time is not precisely exact, but it is exactly true. That is, this is not a weather report; it is more than a best estimate regarding probabilities and extrapolations. True, the true peak is one specific moment that will neither register on your watch as the dot of half-past nor will occur to your eyes as sharply distinct from any of the many moments surrounding it. Yet, it simply will happen - and as close to the expected time as you would ever wish from any commuter train. Unless, of course, the weather does not cooperate and clouds get in the way. Even then, the show will go on. It's just that your ticket won't get stamped.

Earth's shadow will begin creeping over the full moon as early as 8:43 p.m. The full moon will already have risen in the south-east three hours prior. If you face south and look left anywhere around 9 p.m., you will see what it could be like to squeeze two weeks of celestial time into less than two hours. That is, the moon will wane from full to gibbous to half to crescent to void right before your eyes.

By 10:01 p.m., totality will have begun. The moon will sit buried in black until 10:52 p.m. At this time, the moon will begin to claw its way out of the shade. During this accelerated waxing stage - lasting until 10 minutes past midnight - the moon will also be inching its way toward Saturn.

From our perspective, the moon will be trekking west - rightward. Even though Saturn is on the moon's left, it, like everything in the southern canopy, spends its nights moving west. It just does so "faster" than the moon. So, as the moon emerges from obscurity, it will simultaneously bridge the gap to the ringed gas giant.

Daniel Yaverbaum teaches science and is director of Berkshire School's Dixon Observatory.