Astronomers ask Marylanders for help in star eclipse study

September 11, 1998|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Astronomers are asking Marylanders with video cameras to help them study the eclipse of a bright star early tomorrow morning.

At 3: 17 a.m., as seen from Baltimore (a bit earlier south of the city), the sunlit, upper-left-hand edge of the moon's disc will pass in front of a star called Aldebaran. Twenty-six minutes later, at 3: 43 a.m., the star will pop back into view on the darkened upper-right-hand edge of the moon.

It's called an "occultation," and it's the second lunar occultation of Aldebaran this year. The first was the evening of March 4.

With clear skies, the star's reappearance can be seen with the naked eye, although it's better with binoculars.

David Dunham, president of the International Occultation Timing Association (IOTA), said that by precisely timing lunar occultations from different points on the Earth's surface, astronomers are able to develop accurate profiles of the elevations of hills and valleys on the edges of the moon's disc.

The profiles are then used during solar eclipses to help produce accurate measurements of the sun's diameter. Changes in that diameter could signal increased solar activity, and climatic changes on Earth.

This time, Dunham said, "We've organized Howard High School students, and we're getting them out to record it on their camcorders." But anyone with a video camera and a portable radio is welcome to help.

They should videotape the occultation, with the broadcast from WBAL Radio (1090 AM) on the soundtrack to provide scientists with a precise time reference. "It's the reappearance [from the dark side at 3: 43 a.m.] that we want them to record," Dunham said. Aldebaran's disappearance will be too hard to see in the glare of the moon's bright side.

Those videotaping should enclose a diagram of their location, noting the distance to the nearest intersection accurate to within 10 feet. The tape and diagram should be mailed to Sara Parrott, Mount Hebron High School, Route 99, Ellicott City 21042.

Information: IOTA's Web site, at www.sky.net/ (tilde)robinson/iotandx.htm

Pub Date: 9/11/98

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