From: "Greg Crawford" <gc
	(MentoringRequired)
Date: Sat, 1 Apr 2006 19:44:44 +1100
Date: Sat, 1 Apr 2006 19:44:44 +1100

>3. Take flat fields in each color. Do this at the end of the night  
>after you have focused. Do not refocus during the night. 

I would have to question the advice, "Do not refocus during the night". If your
focus changes during the night, surely your focal length has changed, due to
exposure/contraction of your optical tube, and things like dust mites will
project a different image onto the detector. I would imagine refocusing restores
the anomaly caused by the change in the optical tube's length.

- Greg


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