Re: Adaptive optics for a small telescope

From: Gleb (gleb_at_xs4all.nl)
Date: 03/23/05 

Date: Wed, 23 Mar 2005 19:18:28 +0100

Dear Marc

It depends on seeing, place and generally acceptance of what is "the right
thing". Professionals work at good sites and assume that seeing is similar
everywhere. This is one of the reasons why they are so sceptical about AO
for small telescopes. Another reason can be that they just know more ;)).
Yet another possibility can be that it's a kind of commonly accepted
mistake.

I never managed to find any mention of adaptive optics with a 10" telescope,
although everyone knows that it will be not useful, while assuming R_0=5cm
we get to a sensible AO system with 25 actuators! Something should be wrong
here.

To check for myself, I've done a couple experiments with a 25cm Newton in
Delft - which is probably the worst place you could find - a lot of light
pollution from greenhouses and very strong winds from the Norths sea - and
figured out that AO will help even with a very small telescope. Focusing
camera to the input pupil reveals strong turbulence with a scale much
smaller than the mirror size. Star images have clear boiling speckle
structure.

Of course the number of correection modes must be selectable so if tip-tilt
is the only significant term, the system will work on it, but if there is
more and the light is sufficient, then the system must be able to correct
more aberrations.

I assume that amateur astronomers are distributed uniformly over places with
reasonable to good living standards, and these places may have very bad
seeing conditions as these conditions are generally not taken into account
when people choose where to live.

"Marc Reinig" <nospam@nospam.com> wrote in message
news:M_f0e.761$FN4.388@newssvr21.news.prodigy.com...
> For visible light, having subaperatures smaller than 12" makes little
> difference. So for a 12" aperture, you would spend a lot for very very
> little. However, a big improvement can be had by simply correcting for
> tip/tilt at >50Hz.
>
> Marc Reinig
> UCO Lick Observatory
> Laboratory for Adaptive Optics
>
> "Vader" <aries@mercury.kherson.ua> wrote in message
> news:1111565901.392068.199990@l41g2000cwc.googlegroups.com...
>
> > Is the possible to design and then build an AO system for
> > planetary(lunar) works like AO for solar works
> > you referred here http://www.noao.edu/noao/staff/keller/irao/ ?
> >
> > With lesser correction elements (say, 12-16 for 12" aperture) and in a
> > serial manufacturing, I guess, the
> > cost of such a system will be significantly smaller, that that 25K.
> > May be custom DSP will help even
> > more.
>
>

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