Adaptive optics for a small telescope

Thanks everyone. I learned a lot since posting my message on Sunday! See
my remarks below.

West Coast Engineering: The price to the user should be less than $1500.00
for an entry level
system.

It is possible for an "entry level" (F/10, 10 to 19 channels) correction
unit. Sensor camera, electronics
and computer will add a bit

Steve: Is it worth doing anything but tip-tilt in a small system (0.5
metre) ?

Yes, I think so. The right question would be - is it affordable?

Clif Ashcraft: I would be interested, assuming the cost ended up not much
more than a
good CCD camera.

You may need a good camera just to run the AO system.

Chris L Peterson. At an aperture of a meter, you can just begin to achieve
true adaptive
optics- and at that point, only with a few channels. Otherwise, there
simply isn't enough light available for feedback to achieve the
necessary correction rates. for a 25cm scope, you will at best manage a
simple first order correction.

The total amount of light ~ D^2 (D is the mirror diameter). The optimal
number of channels ~(D/R_0)^2. = Amount of light per channel ~ R_0^2.
This basically means that small system needs a small number of channels, but
the available light per channel is the same for a small and a large
systems.

Louis Boyd: Unless you give a dollar value "quite expensive" doesn't mean
much. At
$1k (unit and software, user supplied computer) they'd sell to the
masses. (I'd buy one just to play with). At $10k some would sell. At
$100k few if any who would want it would have the money.

I think $5k for a complete setup without computer.

Ian Anderson: There are two pieces of advice I can offer:
First, keep the final cost of the system under $10 000.
Second, you should try to make it work with F8 systems because most off
he shelf Ritcheys are in this range. If it only woks with F10 or
onger then you will exclude most of your prime market.

F/8 is possible, optics will be more complicated. The argument for F/10 is
simple - AO limits the field forcing F/20 to F/40 to get a good scale per
pixel anyway (AO will improve the resolution so the image must be scaled),
then F/10 looks fine.

Aidan Karley: I wouldn't waste effort trying to make the kit fit into a
1.25" form
factor - most serious amateurs (if you're talking about metre scale
telescopes, then you're talking about quite seriously committed amateurs)
will
have taken the plunge to use 2" eyepieces etc.

The field is going to be small, so 1.25" socket looks OK. There are adapters
for 2" to 1.25"

Louis Boyd: Long range surveillance cameras and spotting scopes are two
that come to
mind. The scintillation distortion looking horizontally though 1000
meters of air in the daytime is often worse than looking at stars though
100km of atmosphere vertically at night. Bigger optics don't help much
or daytime observation as the telescopes are neither limited by photon
rate or the telescope's optical characteristics.

Extended object WF sensor is a complex and expensive device. But then solar
astronomy comes to mind. You can check
http://www.noao.edu/noao/staff/keller/irao/ for some images obtained on an
adaptive solar scope using our deformable mirrors.

The discussion on liquid lens

So far the "liquid lens" technology is not very usable for the AO purposes.
Liquid crystal AO can be much more useful for astronomy as it can be
extremely cheap, but so far it still has some unresolved problems - it is
slow, polarizations sensitive, has strong chromatic aberrations.

Dan McKenna

CMOS based sensors are in a fast lane to low noise performance.
It may be possible to obtain cmos sensors with machine vision processors
integrated in the near future.

I would start by using a bimorph to correct the static mirror errors
first. You would have a knob for tip/tilt, defocus, astigmatism X any Y
etc. That would allow people like me with aging eyes to be able to enjoy
not wearing glasses at the eyepiece.

We have such a system, not for astronomy yet. Look for my name in
the 1 April 2005 (no joke) issue of Optics Letters. Email me for a PDF
reprint.

Membrane mirror is also a curvature corrector, easy to use with curvature
sensors.

Dave: This has been the trend for decades now. The professionals come up
with some
idea for their requirements. Some amateurs with enough resources to try it
for
themselves find a more economical way to do it, but there is either not
enough
interests in the possibilities or enough amateurs with the right resources
to
copy the attempt. If both of these problems are overcome, then it starts
making
significant inroads into the amateur community. Autoguiding, CCD imaging,
even
webcams which can be seen as fast data takes ala scintillation imagers (but
used
for different purposes and goals) were done via this route. Not everything
has
flowed in this direction of course, because the requirements of the
professionals don't necessarily overlap with those of the amateur, but some
have.

Right


Heather ... Assumpt: Why not search for a cure to prostate problems first,
and go back to
outfitting dog sleds with J12 Pratt & Whittney engines? !?

Belongs to alt.prostate.pratt&whittney

Mike Jones wrote in message:
Just a thought: for lower cost introductory AO systems and smaller
apertures (say to 40-60cm), might I suggest a simpler system for
correcting only X,Y tilt and focus? That would help to restore a large
portion of the image quality without the complexity and cost of a
multi-actuator DM, fast processor/FPGA, and laser beacon star.
Curvature is easily sensed using an HOE and narrow-band filter rather
than Shack-Hartmann and directly scaled to generate the drive signal for
a single MEMS actuator curvature-only membrane mirror. The system could
even be partially based on low noise analog circuits to reduce
processing latency and get closed-loop system speeds up to 100 Hz or
more. WFE sensor camera rates are a problem, as the WFE camera must
image at roughly 10X the closed loop rate, or at 1000Hz or more,
reducing integration time and sensitivity. X,Y tilt is a good start,
but adding focus compensation gives noticeable improvement.


I think it's a very good concept for a 25cm telescope, but suspect that more
channels will be needed for a larger instrument. In our systems, using
selectable set of SVD-optimized modes, we have the camera rate of about 4
times the correction rate, not 10 times.

So far the discussion is very useful. Thanks again.