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Gary Emerson
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Gary Emerson - Small Telescope Astronomer for the Deep Impact Mission - The Plan

Gary Emerson observed Comet C/2001 Q4 on the night of May 15-16, 2004 at 3:30 UT.

Comet C/2001 Q4 is a new comet, making its first pass through the inner solar system after being knocked into its present orbit by some good fortune of planet and planetessimal gravitational forces.

Average of three images of 1-minute exposures

Gary took three images of 1-minute exposures and averaged them as shown in the first figure. He used a 20cm F4.0 Schmidt-Newtonian telescope. His CCD camera mounted on the telescope had what is called an R-band filter that allows only the red light to reach the detector.

When we look at this image, we see the coma as a condensed, spherical bright area with a diffuse arc of dust which is the inner 1/2 degree of the tail.

Filtered image of comet nucleus

In order to enhance and pull out information about the comet's coma and its activity, Gary applied an electronic filter that is called a "Sekanina-Larson" or "radial-gradient" filter to show the "jets" near the coma. This filtered image, in the second figure, clearly shows "jets" coming from at least 3 areas on the nucleus.

Comet Tempel 1 will never get this bright but with longer exposures it should appear like this comet around perihelion. Gary Emerson speculates from previous observations of Tempel 1, that we would see an ion tail which would extend in a straight line from the coma, and less dust from Comet Tempel 1, than seen in comet C/2001 Q4. We can all go out and observe the comet a year from now and see if Gary is correct.

Gary's observatory

Emerson, and amateur astronomers like him all over the world will be watching encounter with Comet Tempel 1 through their telescopes. Pictured here is Gary's own observatory, that he has named, E.E. Barnard Observatory after a dedicated and skilled astronomer of the early 20th century who discovered numerous comets and authored "A Photographic Atlas of Selected regions of the Milky Way." (For a biographical description of E.E. Barnard,

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Last Updated: 28 Jun 2010