Comet ISON (C/2012 S1)

Posted by Rod Pommier
on Thursday, December 12, 2013

by Rod Pommier

Pommier Observatory, Portland, Oregon, USA
November 21, 2013
Telescope: Celestron Compustar C14 with f/6.3 focal reducer-corrector. . Camera: Canon 20D: Exposures: Stack of six 15-second exposures at ISO 1600.
After a month of cloudy skies, it finally cleared in Portland on November 21, giving me my first chance to image comet ISON, but by then it was very close to the Sun, rising well inside the morning twilight. Seeing conditions were very poor and it was very, very low on the horizon, requiring me to shoot through a great deal of turbulent atmosphere. Still the color differences between the teal coma and the reddish dust tail are apparent. The comet was moving very rapidly, with a noticeable change in its position on the camera frame within 15 seconds, as evidenced by the amount of star trailing in this 2.5 minute sequence. Exposures taken just after the ones used for this image were overwhelmed by the increasing twilight. The next morning, the comet was so much closer to the Sun that I was unable acquire it.

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