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World's Largest Telescope Up and Running

Posted by ScuttleMonkey on Mon Jul 16, 2007 03:57 PM
from the ncc-2893 dept.
Space Technology
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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  • Worlds Largest Telescope Up and Running (Score:4, Funny)

    by ajenteks (943860) on Monday July 16 2007, @03:59PM (#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, @04:04PM (#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, @04:04PM (#19880961)
    It's not the size that matters. It's how you use it.
    • 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...)

  • 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 :(

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

      by amstrad (60839) on Monday July 16 2007, @04:27PM (#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.
      • 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.)
      • 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

        • 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
            • 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.
    • 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.

      • 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.
        • 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.

      • Re: (Score:3, Interesting)

        by node 3 (115640)
        That's just about the absolute *worst* advice you could give. Someone is interested enough in astronomy to consider a telescope costing a few hundred dollars, but is having trouble justifying the cost, and you tell them to buy a $15k[*] scope?

        Your condescending "Meades are toys" translates to "stay away from astronomy". If someone is interested in the sky, there's nothing better than for them to buy an inexpensive telescope or a nice pair of binoculars. That's an investment even the most casual of intereste

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

    by CanSpice (300894) on Monday July 16 2007, @04:14PM (#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, @05:04PM (#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.

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

      by Ambitwistor (1041236) on Monday July 16 2007, @04:21PM (#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.
  • 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, @04:31PM (#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.
        • 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.

  • Well done! (Score:3, Interesting)

    by Shag (3737) <dan@bircSLACKWAREhalls.net minus distro> on Monday July 16 2007, @04:30PM (#19881233) Homepage
    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.

  • 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.
  • 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, @04:44PM (#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

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

    by Carnivore (103106) on Monday July 16 2007, @08:18PM (#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.
  • 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...

        • 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.
    • OK.

      I was going to moderate as 'flamebait' but then figured I would ask.

      Did you intentionally chnage the word hexagonal from the original article or was it a strange aouto-correct error?

      If so, you need to ad the word hexagonal to your dictionary.

      Otherwise, you have a very strange sense of humor.

      • Re:hexagonal? (Score:4, Funny)

        by Experiment 626 (698257) on Monday July 16 2007, @05:26PM (#19881827)

        Did you intentionally chnage the word hexagonal from the original article or was it a strange aouto-correct error?

        I had a telescope with "12 homosexual segments of the primary mirror for testing and observations" once. Unfortunately, all it was good for is observing Uranus.

    • I wonder if they'll be able to use this to find William Shatner's career?

      They already found that, but it required that they use the Big Ear [wikipedia.org], and listen for the source of a faint but recognizable "Khaaaaan!" [khaaan.com] that's been reverberating about the galaxy for awhile now.

      /P

    • The reason we look for things in the heavens is because it gives us a larger-scale observation than the close up images we get of the way things work from down here. Just imagine how difficult it would be to study a nuclear submarine from the inside, whereas a picture taken from the outside would tell you what you were inside of. Otherwise, you would see passages, pipes, wires and apparatus but it would take a while to figure out what that all did if you'd never seen a submarine before (and were new to the
      • I disagree. The reason we "look for things in the heavens", is the same reason we look for things just about anywhere else. It doesn't matter if it's significant or not, or if anything useful will come out of it. What's important is that by looking, we satisfy our own curiosity.

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