Tuesday, February 24, 2009

Comet Lulin

Click on each image for a larger view
The two images above are of Comet Lulin as it approached it passage near the Earth. Cloudy skies and equipment problems have prevented me from taking its picture before this, but it all came together last Sunday morning.
Surrounding the comet's nucleus is a huge coma of glowing green fog caused by sunlight warming the ices on the comet's surface. You see two tails. The long pointy tail on the rights side is the dust tail, consisting of very small particles of comet dust. The tail on the left side is a gas tail and is actually being blown about in the eddy's of the solar wind (electrically charged paticles coming from the sun). Both tails seem to be pointing directly opposite each other, but in fact, the are both being blown away from from the sun. Only our perspective from the Earth makes it seem that way.
Notice, in each picture, the bright star trail at lower left. The glow you see around the star is actually part of the gas tail making it look foggy. The comet is much closer than the stars, so any part of the comet will block out those stars or make them look foggy.
Also, in the bottom image, notice a dark triangle shape just to the right of the bright, fuzzy star trail. I'm not sure what this is, but I see a much fainter and longer dark area in the top image also. My only guess is that it could be a small tail disconnection (which happens quite a bit).
The top picture consists of 40, one minute exposures combined into one. Each of the 40 images was aligned on the comet's nulceus. The comet is moving pretty fast, almost 5 degrees per day, so in the 40 minutes the stars trailed like you see. The bottom picture consists of 6, 10 minute exposures. All exposures were taken with my 300mm f/4 Canon lens, mounted on my CGE telescope mount. Each image was guided on the comet's nucleus with an autoguider.

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