[Laser] Big adaptive optics

[J Forster]

Terry Morris W5TDM wrote:

> >Do you know if the SBIG unit is just a tip-tilt tracker or does higher
> >order
> >corrections? With a smallish aperture 'scope, say less than 24", tip-tilt
> >and frame
> >selection might produce some very good imagery.
> >
> >-John
>
> Yes, it is just a tip-tilt optical element, so no moving reflective arrays,
> so no high order corrections. The example images do seem to show much
> improvement. Unsure how much this would help in laser communications, but
> would seem to reduce beam wobble on the detector.

Probably not much. The object in optical communications is to collect as many
signal photons as possible with as few noise photons as possible. You could do
this with a tip-tilt tracker and quadrant detector and take the sum of the
quadrants for signal and the differences for tracking, but I doubt it's worth
the effort. Consder a lower noise detector with a larger area instead.

In astronomical imaging, the utility of such a scheme would largely depend on
the seeing at your site. If the isoplanatic regions are large compared to your
'scope aperture, go for it. If there are several regions across your aperture,
you are wasting your time and money.

FWIW,
-John

> If you know who SBIG is
> you may have already seen this, but just in case here are links:
>
> http://www.sbig.com/sbwhtmls/ao8.htm
>
> http://www.sbig.com/sbwhtmls/online.htm
>
> The second link shows the internal working parts of the AO-L
>
> -Terry w5tdm