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TOPIC: Adaptive optics
Blobrana


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RE: Adaptive optics
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Title: Woofer-tweeter deformable mirror control for closed-loop adaptive optics: theory and practice
Author: Donald Gavel, Andrew Norton

Deformable mirrors with very high order correction generally have smaller dynamic range of motion than what is required to correct seeing over large aperture telescopes. As a result, systems will need to have an architecture that employs two deformable mirrors in series, one for the low-order but large excursion parts of the wavefront and one for the finer and smaller excursion components. The closed-loop control challenge is to a) keep the overall system stable, b) avoid the two mirrors using control energy to cancel each other's correction, c) resolve actuator saturations stably, d) assure that on average the mirrors are each correcting their assigned region of spatial frequency space. We present the control architecture and techniques for assuring that it is linear and stable according to the above criteria. We derived the analytic forms for stability and performance and show results from simulations and on-sky testing using the new ShaneAO system on the Lick 3-meter telescope.

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Blobrana


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Corrective lens for the Plaskett Telescope

A Camosun team developed a small stainless steel device that can tip and tilt an optical lens to correct the distortion of starlight travelling through the air.
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Blobrana


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'Adaptive optics' come into focus

Back in 1953, Horace Babcóck had an idea.
The idea of "adaptive optics" has been embraced by a range of scientific applications, not just astronomy
As an astronomer, he was toiling with the problems caused by the Earth's atmosphere.
Light could come from the farthest reaches of the cosmos, billions of light years, and then get impossibly muddled up in the last couple of hundred kilometres as it passed through the turbulent gases that envelop the Earth.
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Blobrana


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GLAO
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Adaptive optics works by focusing on a very bright guide star and measuring its movement, or twinkle. Tiny actuators controlled by computer carry out tiny modifications to the shape of the telescope's main mirror to correct for the turbulence, eliminating the twinkle.
While adaptive optics has worked well for the past 20 years, one drawback is the further away from the reference star you point your telescope, the less effective adaptive optics is.
Now a report in the journal Nature by a team of scientists led by Dr Michael Hart from the University of Arizona describes an enhancement to the system known as ground-layer adaptive optics or GLAO.
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Blobrana


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Ground-layer Adaptive optics
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Five-Pointed Laser Telescope Gives Astronomers Clear Shot to Heaven

Star gazing just got a whole lot better thanks to five green lasers punching a pentagon pattern 15 miles high in the sky.
Devised by an astronomy team in Arizona and funded by the National Science Foundation, scientists have created a method to get crisper views of larger swaths of the night sky.
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Blobrana


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Science with Adaptive Optics on Large Telescopes
Adaptive Optics dramatically improves the performance of telescopes. Over the past few years facility AO systems have become a reality on large telescopes. Significant and important science is being achieved now with these systems on 6 to 10 meter telescopes.
To highlight these developments, AURA has organised a "Meeting within a Meeting" to be held at the June 2009 AAS meeting in Pasadena. We have scheduled over 30 talks for 7 sessions of this MiM to be held in parallel to the 7 regular oral sessions at the meeting. The scientific results that will be presented cover nearly all areas of observational astronomy: Solar System studies, extra-solar planets, proto-planetary disks, stellar clusters and populations, galaxies, black holes, and cosmology.

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Blobrana


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Astronomers at the Royal Observatory in Edinburgh are working with medics to apply technology used to detect stars to treat diseases in the human eye.
Adaptive optics is used by astronomers to cut out atmospheric turbulence around stars to produce clear images.
The technology they use to cut out the "twinkle" of stars can give a clearer image of the retina and help detect disease in the eye.

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