Doug Kerr
Well-known member
An annular solar eclipse will be visible (among other places) along a track across the western contiguous United States late in the day on May 20, 2012.
In an annular solar eclipse, the distance of the moon from the earth is so great that the moon's apparent diameter is less than the apparent diameter of the solar disk, leaving the outermost ring ("annulus") of the solar disk not blocked. The resulting effect is sometimes described as the "ring of fire".
In this case, the moon will be almost at apogee (at its greatest distance from the earth), a counterpart to its having been at perigee (closest to the earth) at the time of the recent "supermoon". Thus the unblocked annulus will be about as "wide" (radially) as is possible.
US cities from which the eclipse is "full" (in the sense described) include Medford, Oregon; Redding and Chico, California; Reno, Nevada; Albuquerque, Santa Fe, and Roswell, New Mexico; and Lubbock, Texas.
Here in Alamogordo, New Mexico we will see almost the full effect.
The track of visibility is shown here in a plot provided by NASA:
http://eclipse.gsfc.nasa.gov/OH/OHfigures/OH2012-Fig02.pdf
The quasi-elliptical outlines show the extent of the moon's shadow on the Earth's surface at three different instants of time during the overall event.
At any place to the east of the line seen through Las Vegas, Nevada, the duration of the visible annular eclipse will be truncated by sunset.
Those interested in determining the exact circumstances at their location for any eclipse (over several millenniums) may wish to use this calculator (also provided by NASA).
http://eclipse.gsfc.nasa.gov/JSEX/JSEX-NA.html
Thanks to Fred Espenak of NASA for the wonderful reference materials.
In later days I will try and provide links to articles about safe visual observation of the eclipse and about photography of the event.
Best regards,
Doug
In an annular solar eclipse, the distance of the moon from the earth is so great that the moon's apparent diameter is less than the apparent diameter of the solar disk, leaving the outermost ring ("annulus") of the solar disk not blocked. The resulting effect is sometimes described as the "ring of fire".
In this case, the moon will be almost at apogee (at its greatest distance from the earth), a counterpart to its having been at perigee (closest to the earth) at the time of the recent "supermoon". Thus the unblocked annulus will be about as "wide" (radially) as is possible.
US cities from which the eclipse is "full" (in the sense described) include Medford, Oregon; Redding and Chico, California; Reno, Nevada; Albuquerque, Santa Fe, and Roswell, New Mexico; and Lubbock, Texas.
Here in Alamogordo, New Mexico we will see almost the full effect.
The track of visibility is shown here in a plot provided by NASA:
http://eclipse.gsfc.nasa.gov/OH/OHfigures/OH2012-Fig02.pdf
The quasi-elliptical outlines show the extent of the moon's shadow on the Earth's surface at three different instants of time during the overall event.
At any place to the east of the line seen through Las Vegas, Nevada, the duration of the visible annular eclipse will be truncated by sunset.
Those interested in determining the exact circumstances at their location for any eclipse (over several millenniums) may wish to use this calculator (also provided by NASA).
http://eclipse.gsfc.nasa.gov/JSEX/JSEX-NA.html
Thanks to Fred Espenak of NASA for the wonderful reference materials.
In later days I will try and provide links to articles about safe visual observation of the eclipse and about photography of the event.
Best regards,
Doug