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Hubble Accuracy Surpassed By Earthbound Telescope

Posted by Soulskill on from the and-we-can-get-to-this-one dept.

randuev writes "A high-speed adaptive optics system helped the Large Binocular Telescope (on Earth) to beat the accuracy of the Hubble Space Telescope's observations. 'A special sensor detects atmospheric distortions in real time and controls the mirror to adjust its position to compensate, effectively canceling out the blurring. The mirror can make adjustments every one-thousandth of a second, with accuracy to better than ten nanometers.' Now, that's what I call real-time. This nifty trick multiplied the Strehl ratio (optical quality) of the LBT by about 80 times. The new system was tested in May and June, so hopefully we'll soon see more space around us in higher resolution on Google Sky."

24 of 87 comments (clear)

  1. Sounds good by Anonymous Coward · · Score: 2, Interesting

    This doesn't mean we'll see better Deep Field images does it?

    I know they used super new adaptive optics but it wont increase the amount
    of light collected.

    1. Re:Sounds good by simcop2387 · · Score: 5, Informative

      While this does mean that it could possibly make some Deep Field images. There is still another problem that makes this possibly intractable. The atmospheric absorption of some wavelengths means that it might still not be able to see certain areas in the spectrum effectively; this could prevent it from being able to produce nice deep field images like the hubble. However this ability to resolve objects that much better means that it could most certainly be effective at searching for planets.

    2. Re:Sounds good by Artifakt · · Score: 3, Interesting

      Probably not. It's not that the binary telescope isn't capable of doing Deep Field work, but the deepest of the deep imaging shots took Hubble keeping its optics focused on a single, apparently dark area of the sky for literally months. Deepest sky search took up most of the Hubble's lifespan during the last few years, and many other projects had to be put on the back burner. Administering big science involves trying to share time fairly for many projects, and I'd bet that many of the first time slots scheduled on the new version of the binary array are promised to the people who were bumped from the Hubble when it became apparent it was a good tool to investigate the very early universe. Other time is doubtless already reserved for those non-cosmologists who want to do other important astronomical things, such as exoplanet searches and resolving what's possible in visible wavelengths of our own galactic core. There's also a need sometimes to do visual backup observation when the orbiting infra-red or x-ray scopes find something unexpected in their wavelengths, and how much time could be borrowed or traded around for this depends on just how weird the other observations are.

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    3. Re:Sounds good by NixieBunny · · Score: 3, Informative

      The amount of light collected is proportional to the area of the mirrors times the transmissivity of the atmosphere.The LST has about 20 times the light gathering area, so it can outperform the Hubble when using its adaptive optics. The mitigating factor in the LST's usefulness is that the atmosphere absorbs certain spectral components.

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    4. Re:Sounds good by mrsquid0 · · Score: 2, Informative

      The big difference between ground-based telescopes using active optics or adaptive optics to obtain diffraction-limited images, and the Hubble taking advantage of the lack of an atmosphere to obtain diffraction-limited images is that Hubble can do this over a large field of view whereas ground-based telescopes can only do this for extremely small fields. This is because the coherence length of the turbulence cells in the atmosphere that are responsible for atmospheric blurring (called seeing) are very small, and the active optics (or adaptive optics) can only correct over areas that are about the same size as the coherence length. So, ground-based telescopes are not going to be replacing space-based telescopes for research that requires fields of view larger than about 10 arcsecond square.

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  2. Re:Impressive! by Denihil · · Score: 2, Insightful

    thats more accurate than you might think. http://hardware.slashdot.org/story/10/07/31/2040226/Microsoft-Tech-Can-Deblur-Images-Automatically?art_pos=13

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  3. Re:More please!!! by Cyberax · · Score: 4, Informative

    Alas, there's no way around the Rayleigh criterion: http://en.wikipedia.org/wiki/Angular_resolution

    We're not going to construct one-hundred-kilometer size telescopes any time soon.

  4. Better than the Hubble, but... by volkerdi · · Score: 4, Interesting

    It's great that atmospheric distortion can be largely eliminated, but just wait until we get some improved optics into space. Hubble has produced wonderful images, but the James Webb Space Telescope is going to be a phenomenal upgrade.

    1. Re:Better than the Hubble, but... by volkerdi · · Score: 2, Funny

      Ah, the treachery of images. This is not a galaxy.

  5. What a testament to the HST... by Black.Shuck · · Score: 5, Insightful

    ...that it was more than 20 years ahead of any Earth-bound telescope when it launched.

    1. Re:What a testament to the HST... by vcgodinich · · Score: 2, Informative

      It wasn't. They have done numerous upgrades to both the optics and the hard/soft/firm ware since launch.

    2. Re:What a testament to the HST... by noidentity · · Score: 2, Insightful

      Wouldn't the same telescope put into space give better images than one on Earth already? So it's partly a testament to the advantage space-based telescopes have.

    3. Re:What a testament to the HST... by noidentity · · Score: 2, Informative

      Grandparent mentioned something to the effect that it was in Hubble's favor that it's still a benchmark for ground-based telescopes, and I was noting that one reason for the Hubble's good performance is simply that it's in space, where it doesn't have to deal with Earth's atmosphere. So the fact that it's still a benchmark is partly a testament to the clarity possible in space.

  6. Sarcasm, right? by mangu · · Score: 2, Informative

    In case my sarcasm detector is giving a false positive, the answer is you don't need adaptive optics for a mirror diameter of 30 cm or less, because at those sizes you get more blurring from diffraction than from atmospheric effects.

  7. Re:More please!!! by John+Hasler · · Score: 2, Informative

    We're not going to construct one-hundred-kilometer size telescopes any time soon.

    There's no particular barrier to the construction of interferometers of such aperature in space, especially at longer wavelengths. You don't actually need to control the separation precisely: just measure it.

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  8. Re:Impressive! by ceoyoyo · · Score: 2, Interesting

    Nope. Except for the basics, deblurring algorithms are usually highly application specific. The one you link to only handles motion blur caused by the camera moving and requires six axis motion tracking.

    Before Hubble was repaired, a different, more general deblurring algorithm was used to help correct the distortion from the bad lens.

    Although, many of the atmospheric distortion correction methods require a guide star. If no guide star is available one is created by shining a powerful laser up into the atmosphere. Such a laser might be handy to have on a cell phone.

  9. Re:More please!!! by Yvanhoe · · Score: 3, Interesting

    Oh, there is a crazy way around it : http://www.spaceroutes.com/astrocon/AstroconVTalks/Maccone-AstroconV.pdf

    : using the sun as a gravitational lens. Sure, it need a spacecraft to go 13x times farther than any spacecraft ever did, but we would get gorgeous pictures. Some people say this may be our only way to ever observe directly exo-planets in details. I am not sure if it enters in the "practical within my lifetime constraint" but if you have 50 more years to go, I wouldn't rule it out.

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  10. Several limitations to Adaptive Optics by syousef · · Score: 4, Insightful

    There are several limitations to adaptive optics, which are by no means a cutting edge technology for large observatories any more. Just about every telescope being built or upgraded today are having adaptive optics fitted.

    One major limitation is that the adaptive optics are only good for small fields of view since you're using a single guide star to calibrate the disturbances in the atmosphere you're correcting. So they are not good for imaging multiple objects or even large single objects (like a single galaxy). Another is that since you're not in orbit like Hubble you have to wait for the planet to rotate, so a deep field would take much longer anyway.

    When we lose Hubble we lose some unique capability. Even successor telescopes that don't work in optical light will not fill that void. Adaptive optics will only be useful in some circumstances whereas Hubble would have been useful in the general case. Oversimplifications like this story don't belong on a techy site like slashdot.

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    1. Re:Several limitations to Adaptive Optics by jarek · · Score: 3, Interesting

      That is why they build MCAO which means multi-conjugate adaptive optics, most often with laser guide stars. It allow for much greater isoplanatic field of view. This is done using (typically) three sensors and the adaptive mirrors projected to different heights in the atmosphere. I wouldn't say is a done deal but it's certainly quite far along and several telescopes are equipped with this stuff. I'm not sure how much real science has yet been done with this technology though but the improvements I've seen my self are very significant but I can't say right now if the Strehl ratio is above one half which I would consider really impressive.

    2. Re:Several limitations to Adaptive Optics by ThunderThor53 · · Score: 2, Interesting

      When we lose Hubble we lose some unique capability. Even successor telescopes that don't work in optical light will not fill that void. Adaptive optics will only be useful in some circumstances whereas Hubble would have been useful in the general case. Oversimplifications like this story don't belong on a techy site like slashdot.

      What I don't understand is why we don't have a direct successor to Hubble. James Webb will be an infrared satellite, not visible light, so I don't see how it's a direct successor (IANAA I Am Not An Astrophysicist). I know of no other satellites that overlap but improve Hubble's coverage. Yes, I understand that today, adaptive optics beat Hubble, but Hubble was launched in 1990. Twenty years later the ground-based coverage bested space-based, but what could we conceivably learn from a visible-wavelength orbital observatory in the next 20 years before the ground-based ones catch up?

      Beyond that, visible-light satellites have the capacity to excite the public like no others. Humans see the visible spectrum directly, and are just more impressed by visual wavelength images than false-color imagines of, say, X-rays. Non-visible wavelengths may be more scientifically important that visible ones, but the visible wavelengths are the ones that the public will pay for.

    3. Re:Several limitations to Adaptive Optics by Genda · · Score: 3, Informative

      So the answer to the first question is, infrared and near infrared are the wavelengths most useful for meaningful astronomy, because they allow astronomers and cosmologists to see through clouds of interstellar dust and gas to the interesting stuff in the clouds, and the interesting stuff hidden behind those clouds. That's why Hubble has both visual and infrared technology on-board. As well, infrared spectroscopy will tell us which nearby planets have the kind of chemistry that indicates the possibility of life. Due to water vapor, the atmosphere is virtually opaque to these frequencies so they must be viewed either from extreme altitude (balloon or very high flying jets), or space.

      The color images that Hubble produces from visual light are in fact heavily altered and do not reflect what the human eye would perceive. Typically the colors being recorded are from the light emitted by Hydrogen, Sulfur, and Oxygen. Hydrogen and Sulfur both emit light in the Red optical spectrum, and if they were presented as the color the human eye perceives would blur together. Instead, the Hubble images view Hydrogen as Red, and Sulfur as Green with Oxygen providing the blue. This gives rich full color images rich in detail and visually stunning color. Images from infrared telescopes are used in exactly the same way, you just can't see those colors. So the representation in either case is not "real".

  11. it's resolution that's better, not accuracy by NixieBunny · · Score: 3, Informative

    Accuracy is too vague a term to use when describing a telescope.
    The adaptive optics increases the resolution of the telescope by eliminating the refractive errors caused by atmospheric turbulence. And the basic resolution of the LBT is better because its 8.4m mirrors are over 3 times the diameter of the 2.4m Hubble mirror.
    The ideal would be a larger mirror in space, such as the James Webb telescope is to be if it works.
    [Disclaimer: I eat lunch with LBT engineers, so I know way too much about the gory details of getting 600 magnetic actuators to work together without breaking glass.]

    --
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  12. Watch the documentary by w00tsauce · · Score: 3, Informative

    http://torcache.com/torrent/DA4B118239E5BC4DF4ACF591D1077AAEC1C4D61B.torrent National Geographic documentary that came out recently about it.

  13. not in the IR though by supernova87a · · Score: 3, Informative

    There's always complexity behind these stories, and it might be interesting for everyone to understand why this development, although a great and useful accomplishment, is not equally useful for all types of astronomy:

     Much of astronomy is being pushed by the need to image deeply in the infrared. For example, to discover the most distant objects in the universe, you need to use near- and mid-infrared wavelengths (because objects that are far away are receeding rapidly, hence redshifted). And for this, mostly what you want is raw photon count, not sharpness (although that would be a "nice-to-have" someday).

    Unfortunately (for astronomy), the atmosphere absorbs heavily in the infrared wavelengths (aside from a few windows, which give us our passpands), and as a result, a 1 meter telescope in space still beats an 8 meter on the ground, in almost every respect (putting cost aside for a moment...).

    At least for infrared work...