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Space Technology

World's Largest Telescope Up and Running 120

Posted by ScuttleMonkey from the ncc-2893 dept.
apdyck writes "ITWire is reporting that the world's largest telescope is now up and running, conducting one-year series of tests. The Great Canary Telescope, located in the Canary Islands, is the largest telescope in the world at 10.4 m (34') in diameter. Not for your average stargazer! 'The reflective telescope, sometimes also called GranTeCan, uses technology called adaptive optics, in which the mirror changes its shape in order to correct distortions of light caused by the Earth's atmosphere. The telescope is part of the Observatorio del Roque de los Muchachos, located on the island of La Palma, Spain, within the Atlantic Ocean.'"
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World's Largest Telescope Up and Running More

World's Largest Telescope Up and Running

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  • Worlds Largest Telescope Up and Running (Score:4, Funny)

    by ajenteks ( 943860 ) on Monday July 16, 2007 @04:59PM (#19880905)

    Nothing for you to see here. Please move along.
    Damn :(

  • Who you gonna call? (Score:4, Funny)

    by imstanny ( 722685 ) on Monday July 16, 2007 @05:04PM (#19880959)
    The telescope is located on top of a volcanic peak that is 2,400 meters (about 1.5 miles) above sea level.

    Someone call Pierce Brosnan. Tell him to bring NASA's experimental locator beacon.

  • Hey (Score:4, Funny)

    by Anonymous Coward on Monday July 16, 2007 @05:04PM (#19880961)
    It's not the size that matters. It's how you use it.

    • Re: (Score:1)

      by Poorcku ( 831174 )
      This is how pop psychology, urban myths mix together. However, some of us may know differently: size matters and more importantly the width. While a Danish sample, it gives an insight. Thanks.

      http://www.springerlink.com/content/wqw46755050017 61/?p=78e25fed12e247b2865ad85a359ecb45&pi=1 [springerlink.com]

      /if it doesn't work, sorry .....but at least the reference is there :)

    • Re: (Score:3, Funny)

      by tgrigsby ( 164308 )
      It's not the size that matters. It's how you use it.

      That's not what your girlfriend told me last night...

      (sorry, couldn't resist...)

      • Re: (Score:1)

        by vraa ( 1086475 )
        I'm going to be honest, I am new here -- but I have to point this out I thought we weren't allowed to have girlfriends on Slashdot?
    • Especially when it comes to telescopes. Larger aperature means more light is collected for imaging, and the more light you collect the shorter your exposure times need to be. And with the limited number of telescopes in the world, multiplied by the limited number of hours actually available for observing at each one (you need a clear sky, on a night near the new moon so that the glare doesn't wash out your images), cutting your exposure times is paramount.

      Larger aperature also means higher resolution images

  • iTWire Strikes Again (Score:2, Insightful)

    by Anonymous Coward
    I don't think it's the largest, at least larger are being constructed. Most lists of large telescopes [wikipedia.org] are measured by aperture (making the GCT third) and while the article notes the problem that other large telescopes can't use their full mirror potential, it neglects to mention that it will be destroyed by the two mirrors on the LBT [wikipedia.org]. According to a BBC article [bbc.co.uk],

    The twins can also be made to work in tandem - as a so-called interferometer - which allows them to mimic a larger telescope that is 85m (279ft) wide.

    It's funny how I can submit a story [slashdot.org] only to have it rejected then have it accepted as two different stories the next week.

  • Only yesterday I was looking longingly at the Meade site and wondering if I could possibly justify a whole eight inch LX200 [meade.com] rather than one of those little ETX series things - I can't help thinking they're the equivalent of desktop routers vs a Cisco 6500. In theory the recent drop in the dollar should make them effectively half price (as I'm in the UK and £1 == $2.03 or so today). Sadly it doesn't seem to work that way :(
    • Amen to that. I thought the price of Software in the UK was bad compared to the US until I looked at 'scopes which manage to run it close. My Celestron 6inch SCT cost £699 over here and Celestron have it on their site with a $150 rebate bringing it down to $936 or about £470. As I recall the LX range is even worse :(
      • Hmmm, you may know the answer to this then -- is there any particular reason I couldn't pay dollars and have it shipped over the Atlantic?
        • Have you got a friend in the States? I'd gladly offer to take it and ship it to you, but I don't actually know you so you might not want to trust me with it.

    • Advice from a (sort of) newbie astronomer (Score:5, Informative)

      by amstrad ( 60839 ) on Monday July 16, 2007 @05:27PM (#19881199)
      My opinion: Keep the cheaper telescope and have more money to spend on accessories such as

      1. Zero power viewfinder, since the Meade 6x30 is worthless. I use a Telerad. They are great and cheap.
      2. A good 8x50 viewfinder. I use an Antares 8X50 Right Angle Erect Image finder.
      3. A good set of quality eyepieces (you can never have enough)
      4. Some filters (light polution, moon, solar, planetary)
      5. decent, but not expensive, pair of field binoculars
      6. etc. I could go on for ever...

      You might be disappointed if you wait a year, buy the more expensive telescope and have no money left over to buy upgrades.

      Some other points:

      • The best telescope you can buy is the one that you will actually use. My first telescope was an 8" equatorially mounted newtonian. I regret buying such a big and bulky scope. It was so akward to actually get to a field. A pair of tripod mount binoculars might have been better for me as a beginner.
      • I suggest not getting all the fancy computer driven stuff. A good star chart and viewfinder can be much more satisfying. If I can convince you of that then you could get more aperture for the same price with a Dobsonian style telescope.
      • Don't fixate on magnifying power. More important is optical clarity and aperture. If you really want magnifying power, you will need more aperture since they are linearly related (google Dawes Limit). Remember this rule of thumb: 50x per inch of aperture.
      • Plan your star gazing nights. Have a list of objectives for each night you go out. Know what's in the sky that night and what you want to look at. Don't simply set up the scope and "surf the sky".
      • Log your observations in a notebook. This will help you become a better observer.
      • Keep the cheaper telescope and have more money to spend on accessories such as...

        No argument with most of what you said but I disagree on cheaper scopes if it means a smaller aperture.

        With telescopes aperture is everything, the bigger the better. A few quid saved on aperture for some accessories will soon be regretted when you find you should have gone for the light gathering power of an 8'' as opposed to a 6'' or 6'' as opposed to 4''.

        • Re: (Score:3, Informative)

          by amstrad ( 60839 )
          Of course you should always buy as much aperture as you can afford, but your aperture budget shouldn't cut into your accessories budget. What I was really saying was: if you are torn between two scopes of the same aperture, buy the cheaper one (i.e. buy a Dobsonian over a Mak)

          However, if you look at planets or the moon, a small aperture high focal length scope is better than the opposite. I moved to urban sprawl, so I can't view deep sky stuff. My 8" Newt is mostly useless. If I could, I'd trade it i
          • Of course you should always buy as much aperture as you can afford, but your aperture budget shouldn't cut into your accessories budget. What I was really saying was: if you are torn between two scopes of the same aperture, buy the cheaper one (i.e. buy a Dobsonian over a Mak)

            I can go with that.

            However, if you look at planets or the moon, a small aperture high focal length scope is better than the opposite. I moved to urban sprawl, so I can't view deep sky stuff. My 8" Newt is mostly useless. If I coul
            • I've always thought that one simpson's episode had it right, but they went too far. Just pick 10 or 15 "light-holidays" a year and turn everything off. Make sure everyone knows about it, and try to make it convenient. Allow low-intensity "glow" style outdoor lighting where safety requires it.
      • great advice! though, as I have a three foot high pile of Sky & Telescope & "Astronomy" here, & speaking as a ten-year veteran armchair astronomer - I have more advice for the beginner observer than I know what to do with ;) (actually the tip about planning what to look at and logging stuff is new to me & sounds good.)

      • Re: (Score:2)

        by syousef ( 465911 )
        Good advice there.

        Department store telescopes are the pits. A good spotting scope is more use, particularly if you're going to be interested in bird watching (the flying kind, not the arrested if ).

        Particularly good advice to buy a Dob. 8" to 12". In my opinion 10" is just right, particularly if you have a large car and don't have medical issues that prevent you carrying some weight (but get a trolley anyway!) Much larger than 10-12" and you need a trailer or Van, or you need to get to you need to align you
      • Or... have a listen to episode 33 [astronomycast.com] of AstronomyCast. All about buying and using a telescope.
    • Buy used. In my experience, you can get an instrument that is as good as new for half the price. Just be sure you examine it before you buy.

      You might not want to spend the money on a computerized drive, but you do want some sort of motorized drive so that you don't have to continually reposition the scope. If you're going to do astrophotography, you definitely want a drive.

      If you're up for a real challenge, grind your own mirror.

      • Re: (Score:2)

        by Rei ( 128717 )
        I recently got a "fixer-upper" scope, and I've been pretty happy with it so far. I've started with a Meade DS 2130-ATS. Since it was an unpopular scope, it's dropped from the original retail price of nearly 400$ down to ~$165 including shipping. That is a newt, 130mm (5 1/8th) aperture, a quality 127mm primary, with a motorized equatorial mount and Autostar guide system.

        Why was it unpopular? A couple of reasons:

        * Poor quality 1" eyepieces that come with the scope.
        * Need an adapter for 1.
    • Check out http://orionoptics.co.uk/ [orionoptics.co.uk] - made in the UK, priced in pounds, very high quality, and you can even take the scope back to Crewe yourself if you have any major issues. Not as sexy in specification as some, but excellent optics (Sky at Night group test winners etc.) Avoids the 1$=£1 scam by definition.

  • No, it's not the world's largest telescope. (Score:5, Informative)

    by CanSpice ( 300894 ) on Monday July 16, 2007 @05:14PM (#19881045) Homepage
    It's not the world's largest telescope. There are plenty of telescopes that are larger than this. The James Clerk Maxwell Telescope [hawaii.edu] is about 5 meters in diameter larger. Arecibo [naic.edu] is about 295 meters larger.

    And then you've got the array telescopes like VLA [nrao.edu] and VLBA [nrao.edu], if you wanted to get pedantic about effective telescope size.
    • They kinda forgot about the whole optical vs. radio thing, didn't they?

      OTOH, does interferometry(?) count when you're announcing the world's largest optical telescope (as in, singular instrument, which I believe is assumed here)?

      /P

      • Re:No, it's not the world's largest telescope. (Score:4, Informative)

        by mythosaz ( 572040 ) on Monday July 16, 2007 @06:04PM (#19881595)
        Doesn't matter.

        It's still not the largest optical telescope. SALT is 11.1m and is, like GTC, made of an array of mirrors. The LBT is 2x8.4m mirrors for an effective 11.8 aperture. Also "bigger" than GTC.

        Sure, the LBT isn't fully functional, but neither is GTC.

        SALT is fully operational. SALT is bigger. Article is WRONG.

        http://en.wikipedia.org/wiki/List_of_largest_optic al_reflecting_telescopes [wikipedia.org]

        • Re: (Score:3, Informative)

          by matmota ( 238500 )
          Well, TFA does mention SALT (South African Large Telescope):

          It is interesting to note that the Hobby-Eberly Telescope, also in the United States--near Fort Davis, Texas in the southwestern part of the state--and the South African Large Telescope have larger mirrors but only a portion of each mirror is able to be used when making observations.
          You might disagree with their interpretation, but they did take the other telescopes into account.
        • If you want to count it that way, then Keck beats the LBT, with two 10m mirrors working together as an interferometer [nasa.gov].

    • Re:No, it's not the world's largest telescope. (Score:5, Informative)

      by Ambitwistor ( 1041236 ) on Monday July 16, 2007 @05:21PM (#19881129)
      TFA (as opposed to the Slashdot summary) says it's the largest visible/infrared telescope. None of the telescopes you've listed are in that category.
      • This is Slashdot. Slashdot got the story incorrect. If TFA had it incorrect I would've left a comment over there. Since they didn't, I didn't.

        Forgive me to trying to correct the writeup on the site on which it appeared.
    • I'm presuming that there should have been an optical qualification in TFA as the ones you list appear, to my untutored eye, to be radio telescopes.
    • Not entirely fair comparing radio telescopes to optical ones here. The radio telescopes are
      *much* larger because the wavelenghts are so much larger, so to match their optical cousins
      in *resolution*, they need to be bigger (either directly, or through aperture synthesis).

      Now, the radio telescopes have much larger sensitivity--they have much larger effective apertures
      than any of the optical telescopes we're talking about here. Many interesting astrophysics
  • Why do they need to change the shape of the mirror? Why can't they just correct the problem using DSP after the fact? Presumably if you know how the atmosphere distorts while taking the image, you can apply the inverse kernel later on...

    • Why do they need to change the shape of the mirror? Why can't they just correct the problem using DSP after the fact? Presumably if you know how the atmosphere distorts while taking the image, you can apply the inverse kernel later on...

      Might be for resolution reasons... from an engineering standpoint, it appears to be more feasible to make minute modifications on a big honkin' mirror, than to try and make changes based on what a much smaller CCD picks up off of it.

      That and I suspect that it would allow them to use non-digital gear (okay, film) to record with the exact same result of data intake, or to swap out visible CCD's with infrared (w/o the additional expense and duplication, or in calibrating between the two different sensors,

    • Re:DSP? (Score:5, Informative)

      by ChaoticLimbs ( 597275 ) on Monday July 16, 2007 @05:31PM (#19881235) Journal
      The reason you can't do this is because the purpose of the telescope is light amplification and magnification. The magnification could maybe work without adaptive optics, but if the light from the object does not get intensified by the large amount of reflector area applied, then you end up with dim images. It's also difficult to get sharp images with DSP as the light coming in contains more information than the sensor can send to the DSP. If the DSP instead applies corrective measures to the optics, you capture the image on the CCD better than if you applied it to only the data. It's a matter of losing the data which is NOT gathered by the CCD as a result of atmospheric distortion which prevents such an approach.
    • The distortions that adaptive optics corrects for result in the light from two places in the sky ending up on the same pixel of the detector array. That's rather hard to correct for with DSP, since you don't know which sky pixel to put that CCD pixel's photons into.

      There are plenty of problems with adaptive optics, however. The folks I work with who work on the LBT say that they've managed to crack four secondaries in a row, with zero intact ones in existence. This is not surprising, given the secondary mir

    • "Presumably if you know how the atmosphere distorts while taking the image"

      The light that forms the image may take hours or even days to accumulate. The distortion is dynamic and will randomly wander about the place during the exposure period, meaning that many pixels will be erroneously "overwritten".

      In other words the photons collected by the CCD cannot be used after the fact to "know how the atmosphere distorts while taking the image" because the distortion is also a function of time.
      • Of all the reasons given in this thread the parent's seems to be the only really accurate one. Adaptive optics works by, for example, looking at a target star (or other object I suppose) and seeing how the image changes due to atmospheric effects, and using that data to predict how the image of the larger field will change. If you are looking for an effectively instantaneous sample then there i s no reason you couldn't achieve the same effect through post-processing of the image. It's when, as the parent sa
        • Thanks for the vote of confidence :)

          "(or other object I suppose)"

          As I understand it the wobble mirror can use a reference star outside the field of view, it's not bound by the target. Theoretically you could use post-processing to build an image but the reason I like wobble mirrors is their engineering "elegance" makes all that complexity redundant.
  • I always wondered how astronomors calculate for distortions, or even realize if there are distortions to their calculator. Like the light data they receive from other galaxies far far away. How do they know if the light went through some medium that cause it to slow down, then went fast again, or if what they are looking at is actually a mirror galaxy that's reflecting something else, mirages, weird anomalies and physics that we sitll dont understand, or any other spacial distortions between here and ther

  • Well done! (Score:3, Interesting)

    by Shag ( 3737 ) on Monday July 16, 2007 @05:30PM (#19881233) Journal
    I've been waiting for this to be completed, since I sometimes work at the W.M. Keck Observatory on Mauna Kea, and the GTC is based on (and only slightly larger than) Keck I and II.

    Keck held the "world's largest" title (among optical scopes) for the last 15 years; it'll be interesting to see whether anything steals the crown from the GTC in the near future.
    • The Giant Magellan Telescope, which is being sponsored by a number of universities, is slated to be 24.5m diameter, with a pretty good fill factor (I think around 80%) is significantly larger and seems to be steady enough politically to survive.
      http://en.wikipedia.org/wiki/Giant_Magellan_Telesc ope [wikipedia.org] [wikipedia.org]

      • Re: (Score:2)

        by Shag ( 3737 )
        Indeed. But since the mirrors aren't segmented a la Keck, it's kind of hard to decide whether it has 1 mirror or 7. :)

        Bring on the (segmented) Thirty-Meter Telescope, I say.

  • During the daytime ... (Score:1, Funny)

    by Anonymous Coward
    During the daytime the telescope is used as a webcam for a local beach.

  • Fresh wallpapers for our desktops!

    Seriously though, it's both incredibly funny and somewhat sad that that seems to be the Hubble's greatest legacy. Still, I'll happily drink to continued scientific progress funded by people's desire for cool pictures.

    • Apparently Big Bird [wikipedia.org] isn't identical in all the Sesame Street franchises - the version from Spain [wikipedia.org] had "a tall, pinkish female bird called Gallina Caponata". But if you're looking for a Grand Canary, and you've got a big telescope, he's probably what you needed...
    • Seriously though, it's both incredibly funny and somewhat sad that that seems to be the Hubble's greatest legacy.

      To a science amateur or geek, sure, but not to an actual space scientist, thank god.

  • First shot! (Score:2, Funny)

    by sl70 ( 9796 )
    There's a great image of the first shot taking with the telescope here [gizmodo.com]

  • Satellite Image of the observatory (Score:3, Interesting)

    by Pigeon451 ( 958201 ) on Monday July 16, 2007 @05:44PM (#19881375)
    http://maps.google.ca/maps?f=q&hl=en&geocode=&q=La s+Palmas,+Spain&ie=UTF8&ll=28.756363,-17.891933&sp n=0.001712,0.002942&t=h&z=19&om=1 [google.ca]

    Pretty cool, you can zoom right in. Guess we'll have to wait for Google to scan the Earth at night so we can see it exposed ;).

  • I thought they were starting to need so much power that the atmosphere was too much of a hurdle, and that's why telescopes like Hubble was built.

    So why are they building this one now and not e.g. helping fund the James Webb Telescope or perhaps some other upcoming plan?

    Is there still much left to discover from the surface of Earth?

    • Re: (Score:2, Interesting)

      by Sperbels ( 1008585 )
      Adaptive optics are overcoming the problems with imaging through the atmosphere. And since you brought up Hubble... all you Hubble-repair-mission fanboys out there might take into consideration that sending up the space shuttle costs somewhere between $500 million and $1.5 billion (depending on who you ask). Now consider that this telescope cost $180 million to build. Can you imagine what kind of ground based optical telescope you could make for $1.5 billion? It would outperform Hubble by leaps and boun
      • Yup, you're correct. There are still things that you can't do on the ground (wavelengths that our atmosphere absorbs) but for the price, ground-based AO observing is very, very good.

        Also, remember that the JWST is not serviceable. If its mirror doesn't unfold, well, that's it. The GTC has 6 spare segments so that a rolling re-aluminising can be done.
    • Why build ground based telescopes?

      (1) They are MUCH cheaper then space telescopes. Maybe 20X cheaper. There ground based scopes only cost as much as a few Hollywood blockbuster movies. We can't afford more then about one space telescope per decade so this means there is more demand for time then a space telescope can supply

      (2) ground based scopes can be very much larger and collect more light

      (3) Adaptive optics combined with the large size means the images are about as sharp from the ground as from spac

  • I work for an astronomy department... (Score:3, Interesting)

    by Carnivore ( 103106 ) on Monday July 16, 2007 @09:18PM (#19883029)
    And I'm getting a kick out of these replies...

    No, really! I work for the University of Floriday Astronomy department. The department has a 5% share of the GTC, and we're looking into another 5%. That may not seem like much, but if you consider one night of 10 meter time can be enough data for a graduate thesis, it's a massive amount of time.

    The IR instrumentation group in my building is building a _giant_ instrument for the GTC. It's called FLAMINGOS-II. IR is where it's at in astronomy right now, so it's neat to be in an up-and-coming department.

    If you guys have any questions about the telescope, I'll do my best to answer them or find out for you.
  • Isn't the world's largest operational telescope always up and running? There may be a new largest, but the old one was the largest back then as well, as were all the ones before it.
  • Wonder why they used Gran Canaria over Tenerife right next door, which has a peak almost twice the height as the highest on Gran Canaria, with Pico Teide being comparable to Mauna Kea... I mean I guess logistically building it might have been easier as it wasn't as steep, but I thought part of the point was to avoid as much atmosphere as possible...
    • It's not on Gran Canaria, it's on La Palma.

      • Re: (Score:1)

        by iainl ( 136759 )
        True, but the GP has a point - Tenerife's highest point is 3717m, compared to about 2400m for La Palma. Also, anyone who has read about the megatsunami predicted from there knows Cumbre Vieja is still active, so I'm still curious about the decision. If I had to guess, it's just due to the fact that there are so many other parts of the Roque de los Muchachos Observatory already up there, combined with the fact that Tenerife is more populated, and so you'd probably get more light pollution.

        • Re: (Score:3, Informative)

          by gsliepen ( 303583 )
          Sure, Tenerife's highest point is higher, but you're not allowed to build anything on the top of the Teide. The current observatories on Tenerife are approximately at the same height as those on La Palma. Yes, the vulcanoes on La Palma are still "active", but it's very benign activity, a little flow of lava once in a few decades. Those vulcanoes are also to the south of the island, while the observatories are closer to the north. The seeing quality at both sites is comparable I think.

          • Re: (Score:2)

            by XNormal ( 8617 )
            > Yes, the vulcanoes on La Palma are still "active", but it's very benign activity

            For an astronomer, there's nothing "benign" about hot air. It causes optical distortions.
  • Strictly speaking the "largest telescopes" will always be the radio telescopes, spanning several square kilometers in some cases. I know a professor at CMU who is currently designing what he hopes will be the largest radio telescope in the world. If they intended to call it the largest *optical* telescope, they really should have said that. "Largest telescope" is quite the claim.

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