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hi Allan.
The big elephant in the room with AO is that it only works on seeing when you are within the "isokinetic patch" - this is the region around the guide star where the atmospheric tilt is consistent from one place to another. If you have the guide star too far from the object you are imaging (eg maybe further away than 1 arc minute for a smallish scope) then AO will not help and can actually make things worse, since it can be correcting one way while the target is being shifted in the other direction by a different bit of atmosphere. Note that 1 arc minute rules out anything but ONAG - you can't do it with an off axis tracking sensor unless you have a very small field of view.
This is not to say that AO is no good - it will do a great job of removing wind induced jitter and residual mount errors up to a few Hertz, but don't expect it to tidy up bad seeing in your system unless you have a very narrow field of view with a big enough aperture to have a reasonable kinetic patch and be able to follow dim guide stars at high frequencies - maybe start thinking 20+ inches.
regards Ray
Last edited by Shiraz; 08-02-2014 at 10:49 PM.
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