From: Michael Koppelman <lolife
	(MentoringRequired)
Date: Sat, 1 Apr 2006 08:47:54 -0600
To: "Greg Crawford" <gc

weeks at a time, myself, although I have a RoboFocus now so maybe  
I'll do it a bit more often.

Michael

On Apr 1, 2006, at 2:44 AM, Greg Crawford wrote:

>> 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.
>
>
>
> _______________________________________________
>