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Re: [ATM] Field derotator
From: "Mel Bartels" <mbartels@bbastrodesigns.com>
" Adaptive optics don't need to compensate for field rotation, as their job is to work over a very
narrow field of view."
It's a nit, but Alt/Az AO systems do need field derotation if they are used for long exposure imaging.
Don Clement wrote
"The low mass, so-called adaptive optics really function as a means to increase the BW in the feedback loop. With the derotator, there is no feedback from the so-called adaptive optics and the
AO can do little if anything to compensate for a nonlinear derotator drive."
No reason an AO system couldn't include a de-rotator, in fact I believe the Keck does just that and was not easy to get working. If you need to control the image plane that closely, you need 2 guide stars for rotation and those can double for Alt/Az tracking and fast tip/tilt won't help much. At some point it is easier to use an equitoral mount.
Greg Jones
http://home.comcast.net/~dac20/dac_001.htm
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