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John Stetson



Location of Photo:

Falmouth, Maine

Date/Time of photo:

May 25, 2011 15h42m and 16h04m UT


90mm h-alpha filter and a webcam


An active prominence caught my attention on May 25th. Many prominences this large are quiescent. This active prom was so dymanic that the changes could be noticed in live time at the eyepiece. The set of two images covers a span of twenty minutes. In that time the ejected hydrogen plasma travelled approximately 32,000 kilometers, a rate of 96,000 kilometers per hour. (This rough estimate is based upon: 1. looking at the arc of the sun's limb to determine the size of the sun; 2. the assumption that 110 earths fit across the sun's angular diameter; and 3. the earth's diameter being about 12,800 kilometers.)


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