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Friday, November 2, 2007

Astronomy: Comet 17P/Holmes: Clear Skies At Last!

Tonight (or more precisely, early this morning, 2007-11-02), the temperature in the skies above Fourmilab fell to a sufficiently low level that all of the clouds, fog, and other gunk froze out and went thunk onto the pavement, clearing the atmosphere for stargazers to regard the most recent celestial wonder, Comet 17P/Holmes.

Last night I was able to observe and take a few photographs of the comet, but the sky wasn't all that transparent. Tonight, however, conditions couldn't have been better, and I exploited them to the utmost by mating a Nikkor 300 mm f/4.5 lens to the D200 digital SLR at ISO 1600 and imaging the comet as seen below.


Note how a star is shining through the tail of the comet, seen end-on from the Earth. The nucleus is visible as a starlike point, and the inner coma, formed by emission from the outburst, is clearly defined. It will be interesting to see how this comet evolves in the coming days. We rarely get to see a comet with its tail pointed so nearly away from us; this foreshortens the tail but also makes it brighter. summing its reflection of sunlight into an extended coma.

This is a once in a lifetime object in the sky. If you haven't seen it, and you have clear skies, don't miss the opportunity. If your skies aren't cooperating at the moment, be patient: the comet will probably remain this bright for at least a week.

Posted at November 2, 2007 02:30