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Old 08-08-2014, 01:55 AM
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Peter Ward
Galaxy hitchhiking guide

Peter Ward is offline
Join Date: Dec 2007
Location: The Shire
Posts: 7,660
I remain puzzled as to why you are seeing better performance with the SX AO turned off, as opposed to it being active. My intention was not to bag SX, but your data does not reflect the results Alan Holmes has published, nor my own qualitative results or that seen by many other (SBIG) AO users.

Alan's data shows a clear improvement & correlation, in both Dec and RA that slowly decreases with angular distance from the guide star ( if only mount errors were being corrected, that would not expect a Dec correlation).

I think it incorrect to say, the physics predicts a first order AO will make things worse.

Quite the contrary.

If the atmosphere's isoplanic patches on the night are at least as large as the telescope aperture, tip-tilt or first-order corrections, provided they are fast enough, will be beneficial....this is exactly how professional systems work prior to applying complex wavefront corrections for higher order components via deformable optics.

On nights when higher order turbulence dominates the image, sure, I'd expect zero improvement...but imaging during tragic seeing, regardless of how good your optics/mount/etc. are, is a futile exercise IMHO.

Suggesting residual mount errors/wind buffeting is all that is being corrected by the AO doesn't offer much insight ( with a system similar to mine )as my mount's PE is around 1-2 arc sec and, being in a dome, there is zero buffeting. Begging the question: if not isoplanic waves, what is being corrected ? That said, I am now curious.

It will be interesting to gather some data, with and without high-speed first-order corrections ( in my case being applied by an AO-8 and AO-X) and similarly quantify the results. I'll happily upload the results when done.
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