2018-11-28
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Mt. Kent Observatory
CDK700

Observer: Rhodes Hart
Processing: John Kielkopf

Image wirtanen_g_00025_dw.fits is one of several taken as the comet moves
northward to a closest approach to Earth in December 2018 that will be best seen
from the northern hemisphere.

This one  is a 128 second exposure in a Sloan g' (400 to 530 nm blue-green)
filter started on this date

DATE-OBS  =  2018-11-28T11:09:38.488

The png version is rotated to put north up, and is shown with a "square root"
stretch to reveal fainter parts of the comet's coma and its nucleus in the same
image.  Since the comet is moving rapidly, its nucleus makes a short streak over
the nearly 2-minute long exposure.  The telescope is tracking stars, not the
commet.

The color image maps 128 second exposures (Sloan i, r, and g) at different
times  to red, green and blue. Each one is centered on the comet, so the nearby
bright stars make red, green and blue spots.  The comet's green color is
approximately correct if it were bright enough to see by eye.