How to determine atmospheric extinction

Use this table to refine your comet observing.

By Michael E. Bakich

Published: October 26, 2009

This photograph of Comet Halley was taken during its closest pass by Earth — 39 million miles.

Photo by NOAO

In the December 2009 issue, I wrote the story, "How to observe comets." In it, I suggest all observers estimate how bright a comet appears. To get the whole picture, however, you must factor in one other thing.

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	Sun	Sun	Moon
RISE	—		—	PHASE	—
SET	—		—	DISK	—