why no true high resolution systems for "jetstream" seeing?

Frank Johnson wrote:
"Chris L Peterson" wrote in message
...

On Sat, 07 Jan 2006 16:16:24 GMT, "Frank Johnson"
wrote:

While it's true that webcams are doing wonders for certain types of
seeing,
in many areas of the US during the Wintertime, the jetstream is
constantly
overhead and even a webcam cannot undo this blurring.

The problem here is the scale length of the jet stream turbulence is
shorter and it is moving past your aperture a lot faster. In principle
if you could freeze the seeing you would eventually get some lucky
frames but the problem is that a webcam isn't fast enough to do it.

these new adaptive optics scopes, like the new pro scope used for solar
imaging, which also incorporate speckle imaging and reconstruction- why
nothing for amateurs? Couldn't blurring of frames (caused by high
jetstreams) be deblurred or "reconstructed" so blurring is minimized.

Speckle is only realistic on apertures of 0.5m and above and requires
narrow bandpass filters to do it. It should be within the abilities of
amateurs to do now on bright stars but I don't know of anyone doing it.

programs that can do this or maybe jetstream effects still can't be truly
nullified.

It is better to get good data in the first place.

Deconvolution techniques can help to reconstruct distorted images, but
there is no certain way to determine just where any given photon came
from. Deconvolution is a sort of educated guess, but it frequently
produces invalid data- and there is no getting around that problem.

It is probably better to say that deconvolution attempts to produces a
representation of what the sky brightness looked like before it was
convolved with your instrumental response function. It is valid in the
sense that what it produces when blurred would look like your
observational data to within the measurement noise. But there are many
such images that meet these requirements and choosing a suitably
represenative one is fraught with difficulty.

Serious problems will arise if you ask the wrong question of your data.

Even in a perfect world these deconvolution codes produce images with
artefacts that are different and unfamiliar and that can be a problem in
eg medical diagnosis.

Hi, yes, I already pretty much understand the current techniques involving
adaptive optics. I myself have experimented on Jupiter by using one of its
moons as a PSF. Then I tried to apply max ent to Jupiter only to end up
with a very noisy and artifact prone result. As you said, there simply
might have not been enough signal to work with.

Signal to noise was probably OK. The thing that would most likely have
caused trouble is that the Galilean moons are not unresolved objects in
any reasonable sized scope. You set a the program problem that had no
reasonable answer.

You need the instrumental psf determined from a bright field star (and
it is rare to have one) or modelled from theory. Any errors in the psf
determination are amplified by any of the deconvolution methods.

Deconvolving with a broader psf than the true instrumental response will
amplify the high frequency noise and also cause excessive ringing on
sharp edges.

Regards,
Martin Brown

Frank Johnson wrote:
Couldn't blurring of frames (caused by high
jetstreams) be deblurred or "reconstructed" so blurring is minimized. With
computers and the power they possess these days, I'm surprised there aren't
programs that can do this or maybe jetstream effects still can't be truly
nullified.

Frank,
If you provide me with an image, I can see what SeDDaRA blind
deconvolution can do for jetstream effects.

Best Regards,
Jim C of Quarktet