To: atm{at}shore.net
From: Andy Saulietis 
Reply-To: Andy Saulietis 


Mel writes,


> >We're now discussing taking out of focus images of bright
> >stars,
>
>Sounds similar to what Benoit Schillings was discussing years ago with
>respect to adaptive optics.  The resulting pattern of light would be used to
>compute actuator commands to null the light into an even gray.
That's the general idea. The problem with doing AO in this manner is that
short exposures, when subtracted, will vary a lot and it would be difficult
to separate the null (grey) image from the brightness changes caused by air
turbulence. For a static test, I'd use fairly long exposures (>60 sec)
in the hopes that the seeing effects would average out, leaving mostly the
distribution of light caused by the mirror itself. AO to control only the
shape of the mirror (not turbulence) might be possible with this technique
to be able to use a *thin* and *large* mirror well enough for a light
bucket type of application. One would have to periodically return to a
bright star to check on the correction.

The real trick, of course, is to be able to interpret the subtracted image
quantitatively to ascertain it's actual shape from the spatial light
distribution.

But a 60" mirror 1" thick with a 1 arc sec images should be
useful for something..;)




Andy Saulietis
ISS Enterprises
PO Box 19
Mayhill NM 88339


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