Regulus Occultation

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The bright star Regulus in the constellation Leo was occulted, or covered, by the first-quarter moon on the night of May 21, 1999 as seen from the continental United States. I took this multiple-exposure photo of the disappearance with a telephoto lens on a fixed tripod. The turning of the earth caused the moon and star to drift "down" toward the lower right in the frame, while at the same time the orbital motion of the moon moved it more slowly "up" toward the upper left to gradually cover the star. Keeping the shutter open, I uncovered the lens at five-minute intervals, and chose an exposure time that would show the half of the moon that was faintly illuminated by earthshine.

This photograph appeared on NASA's Astronomy Picture of the Day site on August 2, 1999.

Date: May 21, 1999
Time: 8:55 to 9:15pm MST
Location: Phoenix, Arizona
Camera: Olympus OM-1 on fixed tripod
Film: Fuji Provia 100 slide
Lens: 200mm
Aperture: f/4
Exposure time: 5 exposures, 5 seconds each, 5 minutes apart
Scanner: Nikon Coolscan LS-10E


Revised: September 2, 1999
Copyright © 1999 Joe Orman
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