[AZ-Observing] Re: Flats and Bias
- From: Brian Skiff <bas@xxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Tue, 17 Jul 2007 12:29:23 -0700 (MST)
>> If twilight has a blue continuum like the sun,
>> why is a flat taken during twilight not suitable during a
>> significant moon night?
The bright Moonlight buisness applied just to the LONEOS telescope,
where we can't take useful twilight flats at all because of the
spped of the system. With ordinary telescopes and using filters
this isn't so much of a problem.
>> would placing a sheet of red cellophane
>> over the objective end of the telescope work...?
Folks have tried all sorts of subterfuges....
>> since there is always the danger of still imaging stars during
>> the twilight, what about slow slewing the telescope in random
>> directions as it is integrating? Am I correct that your reference
>> to dithering is probably doing the same thing?
Yes, although simply leaving the tracking off works, too,
rpovided you have enough images that they come out in the median
combination.
\Brian
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