Now you see it, now you don't
Now you see it, now
June 3, 1999:
On May 21, 1999 the Moon passed in front of the bright star Regulus,
offering North Americans a rare opportunity to view the eclipse
of a distant star without a telescope. Astronomers were hopeful
that thousands of people would not only watch the unusual spectacle,
but also record it using their camcorders. Video tapes of bright
star occultations can be used to make precise topographical maps
of the Moon's limb which, in turn, help scientists use solar
eclipses to monitor the constancy of the sun's diameter and its
long-term energy output.
Amateur astronomers around North America captured
beautiful images of a lunar occultation on May 21, 1999
Above: This animated gif image of Regulus disappearing behind the Moon's darkened limb on May 21, 1999 consists of twenty-eight 2 second video frames. The video was obtained in Houston TX by Mr. Jerry Winkler using an ASTROVID 2000 video camera at the prime focus of an 80 mm Celestron refracting telescope (910 mm focal length). Regulus is a bright dot on the lower left hand corner of the image. It disappears abruptly about half way through the animation loop. A 1.3 MB AVI-format animation is also available. The AVI version features higher resolution images at a 1 second frame rate. Image Credit: J Winkler, Copyright 1999, all rights reserved.
"This was probably the most videorecorded occultation to date," says Dave Dunham, president of the International Occultation Timing Association which issued a call for amateur videos of the eclipse. "I asked everyone who recorded the occultation to send me a message, and so far 40 or 50 have replied. We'll be analyzing the tapes in the coming months as they arrive."
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"The moon was a little larger than my TV screen so I put Regulus in the lower left hand corner and part of the moon in the upper right," explained Winkler. "The extinction of Regulus occurred sharply at 4:31:40 UT in Houston."
Although the occultation was widely touted as a "naked-eye" event, the bright glare of the waxing quarter Moon nearly overwhelmed the weaker glow from Regulus and made the eclipse difficult to see without binoculars or a camcorder with sufficient magnification. A sharped-eyed observer far from city lights might have been able to glimpse the disappearance of Regulus behind the moon's darkened limb, but its reappearance from behind the sunlit hemisphere was impossible to see without a telescope.
Left: This image shows Regulus emerging from the sunlit limb of the moon just after 5:25:30 UT on May 21, 1999. An animated gif image of the reappearance was contructed from twenty-four 2 second video frames obtained by Mr. Jerry Winkler in Houston TX. Regulus is a 1st magnitude blue-white star, about three times as massive as our sun, located 85 light-years away. Although it is very bright, Regulus is far away and much dimmer than the brightly-lit Moon as seen from Earth. The reappearance of Regulus could only be seen through binoculars or a telescope. A 2MB AVI-format animation is also available. The AVI version features higher resolution images at a 1 second frame rate. Image Credits: J Winkler, Copyright 1999, all rights reserved.
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The author wishes to thank Jerry Winkler (Houston, TX), Joe Toledo (San Jose, CA), and Don Newberry (Loxley, AL) who contributed research quality videos of the Regulus occultation to Science@NASA.
International Occultation Timing Association -- learn more about lunar occultations
The Moon occults Regulus -- from Sky & Telescope
Moon Occults Saturn -- Astronomy Picture of the Day, May 8, 1999
Help Map the Moon -- Astronomy Picture of the Day, Sep. 11, 1998
Occultations and rising moons -- Astronomy Picture of the Day, May 13, 1998
X-ray Moon and X-ray Star -- Astronomy Picture of the Day, Feb. 27, 1996
Sunshine, Earthshine at the Lunar Limb -- Astronomy Picture of the Day, May 30, 1996
The sky on Friday May 21, 1999 -- from EarthSky.com
The Nine Planets: the Moon -- from SEDS
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