Lunar eclipse is great prime-time viewing

COFFEE WITH WARREN, with Warren Harbeck
Cochrane Eagle, October 20, 2004

On the evening of Oct. 27, finish your dinner dishes and homework early, go outside, face east, and – weather permitting – prepare to be awed by one of the timeless wonders of the night sky.

For an hour and a half, the sun's brilliant floodlight on the moon will be darkened, and earth's nearest neighbour will stand centre-stage, dimly lit in the burgundy glow of all of earth's sunrises and sunsets.

This is the eclipse of the moon, the last visible throughout North America till 2008.

A lunar eclipse occurs when the moon passes through the earth's shadow. It only happens at full moon when the moon is directly opposite the earth from the sun. It can be observed with the naked eye, although a pair of binoculars will add to the viewing pleasure.

Lunar eclipses are not to be confused with solar eclipses. A solar eclipse – the eclipse of the sun – occurs when the moon passes between the earth and the sun, blocking the sun's rays from striking the earth. Solar eclipses should never be viewed with the naked eye.

For next week's event, folks in southern Alberta will start seeing a bite taken out of the moon at 7:14 p.m., about an hour after sunset. This is the beginning of the partial eclipse, as the moon, moving west to east in its monthly journey at the rate of about one moon diameter per hour, makes first contact with earth's shadow. The bite will grow larger till the moon is totally enveloped in shadow at 8:23 p.m.

The total eclipse will last till 9:45 p.m. During this time, as the moon passes through the centre of earth's shadow, it may appear anywhere from nearly invisible, to dark gray, brownish, deep red, rust-colored, or shades of amber. Near the edge of the shadow, the moon may appear brighter, possibly yellowish or bluish.

Then the moon will slowly emerge from the shadow, till at 10:54 p.m. the eclipse will be over.

There are many fine publications and Web sites available for understanding this heavenly phenomenon. One book I always keep at hand is a spiral-bound edition of Terence Dickinson's NightWatch: A Practical Guide to Viewing the Universe. This book is for anyone fascinated by the night sky, beginner or serious astronomer. It has a whole chapter on solar and lunar eclipses, with spectacular photographs.

Among the Web sites that deal with next week's lunar eclipse, I'm especially impressed with two:

The first is maintained by Sky and Telescope Magazine. Go to skyandtelescope.com and follow the link under "Observing" to the page "October's Ideal Lunar Eclipse," by Alan M. MacRobert.

One of the delights of this article is its helpful explanation of how the moon gets its beautiful colours during a lunar eclipse. "The strange light on a totally eclipsed Moon," he writes, "is the combined illumination from all the sunrises and sunsets ringing the Earth at the time."

He also provides suggestions on how to photograph a lunar eclipse.

The other Web site you will want to check out was developed by Fred Espenak for NASA. Go to sunearth.gsfc.nasa.gov and follow the links to the lunar eclipse site for Oct. 27.

This may be the most comprehensive popular Web site dealing with this month's eclipse. It includes time charts, maps, diagrams, and predictions about future lunar eclipses. It also lists links for viewing live webcasts of the eclipse, just in case Cochrane's weather fails to cooperate.

Note that the NASA Web site refers to times as GMT – Greenwich Mean Time. To calculate Alberta time (MDT), subtract six hours.

Of course, ours is by no means the first generation to be awed by the moon's mysterious disappearances. Way back in 331 BC, one early-evening lunar eclipse caught the attention of historian Curtius.

"About the first watch the Moon in eclipse, hid at first the brilliance of her heavenly body," he wrote, "then all her light was sullied and suffused with the hue of blood."

To take full advantage of this fall's lunar eclipse from the outset, find a dark area with an unobstructed view of the eastern horizon, dress warmly, and enjoy!

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