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."
Plus, time on big scopes is limited and there's a huge demand. Even the Palomar 200 inch scope, with optics that aren't as good as what we'd make today, keeps a full schedule of research. And that thing has to be 70 years old or something close to that. Big research scopes never become obsolete in the sense that nobody wants to use them.
If tits were wings it'd be flying around.
Well this doesn't quite seem like news, not even cutting edge ... currently their are plans in the work to build CELT, a 30 meter telescope with a deformable secondary mirror, while using a laser guide star.
... however there is a project at Lawrence Livermore National Labs where they have a 15ft. mirror that folds up to the size of a hat box. They brought in an origami expert to figure out how to do this. (Sorry I don't have a URL, I just have a print copy of the monthly LLNL newsletter)
... it really needs a Laser guidestar ... but there is only working Laser guidestar ... which is at Mount Hamilton
The laser guide star allows us to view the dark portions of space, where as the UofA system requires that the object be near a natural guide star (namely a star big enough and bright enough that we know where it is supposed to be before it is deformed by the atmospher)
Land based telescopes are great, and the only reason for space-based ones is to collect the wavelengths of light that are filtered out by the atmosphere. But getting a telescope as large as the 30-meter CELT into space is a big challenge
Anyways, the UofA telescope isn't really news
Sig Nazi- "No Sig for you, come back 1 year."
AIUI, based on reading about other telescope plans, but I think it applies here, they don't try and measure and pre-compensate for distorting influences, rather they use the image to determine what the current distortion is, and compensate for it.
Of course, to do this you need to have something in the image which you know how it should look (bad grammar there). Eg you arange your picture to contain a point source like a distant bright star and the nebula you are interested in. Then you twiddle the optics until the star is as close to a stationary point as you can get, which should have the effect of making the nebula clear.
If you have used an auto-focus camera and found that some things are hard for it to focus on, you may have used the same trick, pick somethig near what you want in focus, focus on that and then take your picture. Imagine doing that gazillions of times per second.
I remember reading a proposal to put optical targets in orbit to help with this process. That way they wouldn't be limited by the need to find a bright point source near what they are interested in.
_O_
.|< The named which can be named is not the true named
However, better resolution doesn't have to be for imaging. There are a handful of optical interferometer projects (ground and proposed space) that have amazing resolution and are used for very narrow field of view imaging as well as astrometry. In this case, more resolution == better telescope (at least for its intended application). This is why, for instance, NASA has the JWST as well as SIM. Different scopes for different folks.