Slashdot Mirror
A Ground-Based Scope That Flexes For Better Focus
Steve0987 writes "EE Times Online has an interesting article on a deformable telescope mirror that the University of Arizona has built. It uses 336 magnetic coils to deform the 2 foot secondary mirror and change its shape to compensate for everything from wind blowing against the telescope to atmospheric aberations. It is purported to provide 3 times the resolution of the Hubble telescope. (And you don't have to go into space to fix it."
b4 u think hst is obsolete, note that the adaptive optics can only compensate the waveform deformation in a very narrow field. this is good to study binary stars, quasars, galactic neclei etc which are essentially tiny dots in the sky. hst has no waveform deformation at all, so it can use wide field imaging with full resolution; something which is not yet possible with adaptive optics. also adaptive optics requires that either the object is very bright itself or it has some bright objects very close by. hst has no such limitations.
"Is it the 550Hz sampling rate?" No. It's the 40KHz sample rate and 550Hz update rate (updating the actuators). I imagine they do some heavy shit math on the 40KHz data between each update of the outputs.
The mil scope has active [vibration only?] cancellation where the civvy model has a unique on-scope mirror which is reshaped to compensate for vibration and atmospheric conditions. BTW, the link you cite says the mirror for the mil job was made by the U of A... I think they've one-upped the air force.
Heh, a /. article that covers something I worked on!
> but it sure looks like they're making claims of being first when they aren't.
This *is* a first because the deformable mirror *is* the secondary mirror, which all modern reflecting telescopes have nowadays.
The Starfire Optical Range (SOR) telescope and all other adaptive optic (AO) systems use about 10 to 20 additional reflections between the sky and the detector to do the AO correction - it may be a 3.5 meter telescope, but it's more like a 1 meter telescope in light-gathering power after 20 bounces for light loss are taken into account. The SOR telescope was also optimised for taking high resolution picutres of fast moving objects in low earth orbit *think spy satellites*
The other bonus is that the new system is *excellent* for taking near infra-red pictures of the night sky, and a lot of recent astronomy is driven by a need for a good AO system in this regime (about 1 to 10 microns).
Dr Fish
> Note: I'm a UofA Alum, but their screwup on that mirror deserves mention whenever they do something right...
I'm trying to check my history, but wasn't the Hubble mirror made and tested at Perkin Elmer? I don't remember the U of A being involved with Hubble's mirror. It was an error in the test equipment at Elmer that led to the spherical aberration being put into the mirror...
You may be thinking of the NICMOS camera, which the U of A was involved with, and that had a problem with cryogens boiling off too rapidly, but that was corrected a while ago...
Dr Fish
> on its 640-mm (2.1-foot) 3.5 Meter deformable mirror
You're comparing the wrong things together.
It's not clear in the article, but the Starfire telescope has a PRIMARY mirror diameter of 3.5m, but the Steward telescope has a diameter of 6.5m.
The flexible secondary mirror of the Steward is the 640mm number you've compared with the primary mirror of the starfire telescope.
Hope that clears it up for you!
Dr Fish
"Introduction to Adaptive Optics", ISBN 0-8194-3511-2
"Principles of Adaptive Optics", ISBN 0-12-705902-4