Lunar eclipse on tap for early risers

Tuesday, August 14, 2007

Wow, what a marvelous display the Perseids put on this year. Definitely worth waiting up until the wee hours of the morning. I put in a little extra observing time for Jupiter, Mars, and some of the Messier objects in the southern sky during breaks in Perseid-looking. Saw some of the winter constellations peeking over the eastern horizon too.

Speaking of observing, have you been observing that the days are getting shorter? On the summer solstice, June 21, sunset was at 8:18 pm, Wednesday, Aug. 15, it will set at 7:44 -- a loss of about 34 minutes. Of course the Sun is rising later each day, too, as its rising and setting points move farther south along the horizon. In about five weeks, the Sun will rise due east and set due west, and autumn will officially commence.

While we await shorter days, longer nights, and cooler weather, our skies are blessed with a total lunar eclipse in the early hours of Aug. 28. A lunar eclipse can only occur at Full Moon, and only if the Moon passes through the shadow of the Earth.

This shadow is composed of two parts, the first is the penumbra, an area where the Earth blocks some, but not all, of the Sun's light. Inside the penumbra is the umbra, an inner cone of relative darkness where the Earth blocks all direct sunlight.

A total eclipse occurs when the Moon passes into and through the umbra, the inner cone. During a full, total lunar eclipse the color of the Moon will change from the bright white of reflected sunlight to a brick red, reddish orange , brown, or even black depending on atmospheric conditions.

Roughly half of the Earth gets a decent look at a lunar eclipse. The good news is that, for this eclipse, we are in that good half. The bad news is the timing: the start of totality is 3:52 am MDT (4:52 CDT). Not only do we have to get up early (or stay up all night), the eclipse is not finished before the Moon sets. Even so, it is worth losing sleep to see.

You don't need anything to watch an eclipse, just your eyes, and you won't even need a dark place, your backyard will do, if it has a clear horizon in most directions. Even so, binoculars or a telescope will enhance the view.

The Moon will enter the penumbra at 1:51 am MDT. This phase of the eclipse will hardly be noticeable.

Totality, when the shadow starts to take a chunk out of the Moon, starts at 2:52 am and will last until 5:22 am when light again begins to reach the surface of the Moon. The Moon, however, will set while still in the partial eclipse phase.

If weather or your sleep schedule preclude viewing this eclipse, no problem. Another total lunar eclipse takes place in February of 2008. This will be a prime-time eclipse for us. It will start in the early hours of the evening and end before midnight.


Venus and Saturn have left the evening sky and are passing the Sun in preparation for entering the morning skies. A growing crescent Moon will visit Spica, the brightest star in Virgo, the Maiden on the 17th and continue eastward to join Jupiter and Antares on the 21st. Be sure to mark the early morning hours of Aug. 28 to catch the march of the Earth's shadow across the Moon's face.


More astronomical blatherings.

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