Slashdot Mirror
Telescope Will Have Images 10X Sharper Than Hubble
jangobongo writes "After a 20 year struggle, the University of Arizona's $120 million Large Binocular Telescope was dedicated last week. This unique telescope will have twin 8.4-meter (27.6 foot) mirrors that sit on a single mount. Using methods similar to a medical CAT scan, a technique of "tomographic" image reconstruction will be used to produce pictures 10 times sharper (example) than the Hubble Space Telescope for a fraction of its $2 billion dollar cost."
Here is a particularly good description of the LBT (Large Binocular Telescope) from an article in the Eastern Arizona Courier.
The LBT is made up of two 8.4-meter mirrors, which, when in place, will bring together the light, creating sharper images of faint objects in space. One mirror is in place at the Mount Graham International Observatory, and the other will arrive next spring. Each mirror is designed in a manner that allows it to reach the same temperature as the outside air up to two hours faster than any other mirror design. Under the solid glass surface are openings in a honeycomb pattern. Cold air is pushed up through those openings, cooling the glass to the desired temperature. The sooner the glass cools, the more science can get done, which is good from a business standpoint, assistant project director for LBT Jim Slagle said.
Not everbody is happy about this, though. The Apache people are protesting the use of the site for the telescope.
The U of A is finally dedicating it's Large Binocular Telescope (LBT), formerly called the Columbus Project, after years legal and money problems and at least a year before actual completion. (The U of A changed the name of the project after realizing it wasn't such a popular idea to name it the Columbus project and then, against the wills of the Apache people, place it on their most sacred site on top of the mountain.) The LBT is mainstay of the project. Investors will be wined and dined on Fri. at the La Paloma resort in the Catalina foothills and bused up to the mountain on Sat. to tour the scope site. Our job is to show the investors how controversial and unpopular this project is... and has been for decades.
http://www.busyweather.com/
Why not? The point of Hubble is to be diffraction limited rather than seeing limited (due to being above the atmosphere).
Adaptive optics makes putting telescopes above the atmosphere unnecessary (or less necessary, AO is still in it's infancy).
If you can build a superior instrument for the cost of a single Hubble reservicing mission, why is it unfair to compare the price/performance to Hubble? No it doesn't have the same "coolness" factor that Hubble has, but as an astronomer, I don't really care about that.
Doug
Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
Seeing limited means limited by the turbulence in the Earth's atmosphere. There are lots of cells of turbulent air in the upper atmosphere that make the stars twinkle -- this is the bane of ground based observing. The whole point of putting a telescope in space (at least in the optical bands) is to avoid this 'twinkling' effect. Astronomers call this seeing, and go to great lengths to try to build telescopes in places (like Hawaii, Chile, etc.) where the seeing is good. Good seeing usually means about 1 arcsecond -- this is much better than what you see when you go out in your backyard in most places. Pretty exceptional seeing is 0.5 arcseconds or better. HST, which is above the atmosphere, is not limited by seeing, but IS limited by the size of it's mirror. Because of the wave nature of light, every telescope has a limit on how sharply resolved it's images can be based on the diameter of the telescope. A ground based large telescope, like Keck or the LBT, would always have better image quality that Hubble IF you could get that pesky atmosphere out of the way.
Now, in the past few years something called adaptive optics has become popular. It consists of techniques to correct for the twinkling and make the big, ground based telescopes, see more clearly (in some sense) than HST. The problem is that this only works in the infrared -- not in the optical bands. So we can now do better in some ways from the ground than in space, but not at all wavelengths.
The claim that the LBT is x times better than Hubble is somewhat misleading. Again, this only applies to the infrared -- NOT the optical. And even in the infrared the story isn't really that simple -- with adaptive optics (at least) you tend to get a narrow core that is really, really well defined, much better than Hubble, but then there is a large skirt of less corrected light around the sharply defined core. So for some purposes adaptive optics isn't really better -- like if you need to measure all of the light. This is (naturally) being worked on.
Another problem is that for most adaptive optics systems you need to have a pretty bright star right next to what you are looking at -- which isn't true for most parts of the sky. People are bulding laser systems that create artificial bright stars wherever they want to look, but they aren't as common, don't work as well, and are difficult to use -- among other things you have to file an observing plan with the FAA to make sure you don't accidentally shine the thing at a plane flying by.
You shouldn't have this problem with the LBT, but I don't know about the previous one. And, as far as I can tell, it also only works in the infrared.
Are you for some reason under the impression that the sole purpose of the Hubble is to be a large object orbiting Earth?
Mathematics is made of 50 percent formulas, 50 percent proofs, and 50 percent imagination.
Adaptive optics is great but what about UV and IR spectrography and imaging? One of the HST's best features is the ability to image and get spectrums from UV all the way to IR. Ground based telescopes only get a fraction of the spectrographic information the HST receives. A great deal of the recent information regarding supernovae has come from UV images and spectra from the HST as have excellent H2 and dust maps of our own galaxy. For cosmological structure observations ground based telescopes with adaptive optics can be wonderful tools but at the same time there is a definite need for observatories outside of the atmosphere.
I'm a loner Dottie, a Rebel.
"theres not air in space..."
But there's an Air in Space Museum?
Unknown host pong.
The story gives the impression that the LBT will completely replace Hubble, and do a better job, while being vastly cheaper.
This is an overstatement. There is lots that Hubble can do that no other telescope can, being a unique combination of aperature (light gathering power and resolution), instruments (many wavelengths, imaging and spectroscopic) and being above the atmosphere (no 'seeing', no atmospheric absorption or emission in UV and IR.)
(This is not to downplay the LBT - doing better than HST in some aspects, and as well but much cheaper in others, is very valuable.)
Having quickly scanned the website for this telescope, I can't see how they are counteracting the bluring of 'seeing' (atmospheric turbulance). It is inconceivable that they have neglected it, but I don't see where. Adaptive optics can help, but have limitations of their own.
Another limitation of the LBT is that the high resolution reconstruction will require 3 observations at different times - so it only works well with non-time-varying targets. This is a minor limitation, however - a large majority of targets for which you want high resolution are non-variable.
(IWAA: I was an astonomer. PhD, but no further.)
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
It will permit formation of images of sufficient sharpness (diffraction-limited) that the planet could be detected against only a low surface brightness halo of residual scattered light. In this manner, a Jupiter-like planet could be detected, if present, around some fifty of the nearest stars. The interferometric mode will enhance the planet/background contrast even further, thus increasing the number of candidate stars and the sensitivity of the survey. The direct detection of such a planet would surely be counted as one of the major steps forward in determining the likelihood of life existing elsewhere in the Universe and in understanding our place in it.
So, gas giants, but no mention of anything Earth-like. Too bad. I'd definitely be psyched to someday hear about "Earth-sized planet discovered about an AU away from a Sun-sized star."
but as an astronomer,
/me ducks
so, you took up space in college eh?
"goodbye and hello, as always" ~Prince Corwin, from Zelazny's Amber series
A requirement on all observing proposals to Hubble is that the observation can't be done by any ground based telescope. This is so we don't waste the expensive telescope time on something that can be done by the chearper telescopes. So when LBT starts operation, there may be some observations that would have been done on Hubble going to LBT instead. But certainly not all of them.
In any case, the way things are going at NASA HQ, it'll be lucky if Hubble is still operating by the time LBT starts observing with both mirrors.
I have seen several stories of telescopes that promise equal-or-better than hubble images. Usually there are some drawbacks. Here are some of the drawbacks that came up:
1. Limited range of sky
2. Frequencies different than hubble, such as only infrared.
3. Only works near bright stars due to "guide-star" anti-blur technology.
Let's see if new techniques get around these.
Table-ized A.I.
it doesn't really count as a plus if the earthside telescope can beat it(quite the opposite).
Sorry, you are missing the point about the HST. It is doing things that no earth based scope can ever do. Because its above the atmosphere, there are NO artifacts of atmospheric band limiting it has to deal with. That effectively continuous broadband spectrum, extending from the near ultraviolet to the far infrared allows it to take in and process light that is 100% absorbed by the moisture and other contaminants in our atmosphere.
All things considered, that effect alone is worth, and I'm making a SWAG here, at least half an F-Stop over the whole operating bandwidth, and many F-Stops of increased sensitivity at some frequencies.
No, the HST is not doing what the Webb can do when and if it gets up, but then the Webb cannot do much of the HST's job either, each being designed for completely different objectives.
And if your congress critter doesn't understand that difference, work to elect one that does, its all valuable science.
Cheers, Gene
As another astronomer, I'll chime in that it's still apples and oranges. We couldn't build the LBT 15-20 years ago, and Hubble would be cheaper and better if we built it now. The points about the UV coverage of Hubble are especially good ones -- LBT will never work in the UV, and some science requires the UV. Furthermore, the results from the LBT will not be simply "10x" better resolution -- there is atmospheric effects to worry about and compensate for, and there is only a single baseline (to get 360 degree interferometry will require quite extended observations to get what astronomers call "coverage in the u-v plane).
Will the LBT kick astronomical ass? Almost certainly.
Will Hubble still be able to do things LBT can't? Yes, indeed.
Will the LBT be able to do things Hubble can't? Of course.
The Hubble cost-analysis is way more complex than these simple comparisons on slashdot always seem to apply. At this point, the appropriate questions are things like, is Hubble worth the cost of maintaining? Does it still provide a unique capability? What is the value of that unique capability? When can a bigger, better replacement fly? Etc.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)