Volume 16, Issue 33 - August 14 - August 20, 2008

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Sky Watch by J. Alex Knoll

By the Light of the Moon

Three planets follow the setting sun as the full moon rises

Evening twilight and a clear view to the west finds Venus, Saturn and Mercury tightly clustered in the wake of the setting sun. The three are closest together the night of Thursday, August 14, with Venus brightest and highest, golden Saturn a degree lower and steady-shining Mercury another degree closer to the horizon. Timing is everything here, as the three don’t emerge until sunset, at 8pm, and disappear a little more than a half-hour later. Binoculars or a telescope trained above the western horizon will increase your likelihood of spotting this triumvirate.

If conditions mar your viewing of these three planets Thursday, they reappear Friday, with Mercury a little higher and Saturn now closest to the horizon. By Saturday, Mercury is equidistant between Venus and Saturn, with little more than two degrees to either side.

As the sun sets beneath the west-northwest horizon Saturday, the full moon crests the east-southeast horizon. Unlike glimmering stars, the moon has no light source of its own, and is instead illuminated by reflected sunlight. When full, the moon, the earth and the sun are all aligned, with Earth smack-dab in the middle. As the sun’s rays stream around the planet, they hit the moon head-on, bathing its entire visible face in light.

As the moon rotates around Earth, the alignment between the three orbs shifts, and so does the angle at which light hits the moon, resulting in the moon’s phases. By the time the moon reaches new phase, it is directly between Earth and sun, rising at the same time as the sun and awash in its glare.


Illustration: © Copyright 1925 M.C. Escher/Cordon Art-Baarn-Holland; Graphics: © Copyright 2007 Pacific Publishers. Reprinted by permission from the Tidelog graphic almanac. Bound copies of the annual Tidelog for Chesapeake Bay are $14.95 ppd. from Pacific Publishers, Box 480, Bolinas, CA 94924. Phone 415-868-2909. Weather affects tides. This information is believed to be reliable but no guarantee of accuracy is made by Bay Weekly or Pacific Publishers. The actual layout of Tidelog differs from that used in Bay Weekly. Tidelog graphics are repositioned to reflect Bay Weekly’s distribution cycle.Tides are based on National Oceanic and Atmospheric Administration and are positioned to coincide with high and low tides of Tidelog.

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