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World's largest telescope wins early funding

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Plans for the world's largest optical telescope are coming into focus, thanks to the authorisation of €57 million ($74 million) in funding to design the European Extremely Large Telescope.

A consortium of 11 countries participating in the European Southern Observatory (ESO) has approved the funding for the E-ELT, which is expected to cost between €800 million and €1 billion ($1 billion to $1.3 billion).

In July, ESO created an office to design the telescope, with initial plans for its mirror to measure between 30 and 60 metres across.

Now plans for the telescope, which will operate at optical and infrared wavelengths, are coming into sharper focus. A design approved by more than 250 ESO astronomers at a four-day meeting in Marseille, France, earlier in December calls for a 42-metre composite mirror. The mirror will be composed of 906 hexagonal segments, each 1.45 metres wide.

New era

Their light will be channelled to an "adaptive optics" system, chiefly composed of a smaller mirror whose shape can be distorted by tiny actuators. The system will help correct for image fuzziness that occurs when light passes through Earth's atmosphere.

The design phase should last three years, followed by the start of the building phase. If all goes well, the E-ELT will start operating in 2018.

It will be more than 100 times more sensitive than today's largest optical telescopes, the largest of which are the twin 10-metre Keck telescopes in Hawaii, US. The E-ELT will shed light on the planets around other stars, the first galaxies in the universe, colossal black holes and enigmatic phenomena such as dark energy and dark matter.

"This is really the beginning of a new era for optical and infrared astronomy," says ESO director general Catherine Cesarsky.

Source: New Scientist

Full article: http://tinyurl.com/y5f5s2

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European Extremely Large Telescope.

So we've had the very large array, now the EXTREMELY large telescope. What are they going to call the next one...? Stonkingly large telescope :)

A consortium of 11 countries participating in the European Southern Observatory (ESO) has

Southern Observatory? This means Southern hemisphere then... oh well that's a visit out the question!

Good find Steve

Ant

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Google the "Overwhelmingly Large Telescope" and see what you come up with. Astronomers were never good at naming things. These are the guys that looked at Jupiter, saw a strom 3x the size of Earth and called the "The Great Red Spot". Jeez. :cyclops:

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They are going to run out of adjectives soon. Maybe they'll move into expletives? The blumming Massive Telescope (just to keep it polite, I'm sure there are others)?

The FHT... :)

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Seriously I realy hope they fund it thru to completion. How good is adaptive optics at visual wavelengths anyway? I read it's quite good at infrared but not so hot at shorter wl.

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But why are they putting it on earth?!? I mean, you spent a billion on a new scope, then plonk it under a huge bank of clouds!! Surely it woudl be more worthwhile spending the money on transporting a smaller telescope to set up on the moon, or in space, where there is going to be no problem with all the usual set-backs we have here.

I don't know.

Andrew

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But why are they putting it on earth?!? I mean, you spent a billion on a new scope, then plonk it under a huge bank of clouds!! Andrew

They're not putting it in Scotland is the short answer. There are (no, really) places where the clouds are very rare things indeed on this planet of ours.

You don't have to fly a shuttle up to change the eyepiece if it's bolted down to a big mountain plus you can make it loads bigger. The Hubble is only a small instrument compared to ground based stuff and some stuff needs aperture.

Captain Chaos

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saying that..you could build it on the moon?yer would cost loads more but it wouldnt suffer from cloads being in the way.you could build it loads bigger and could still control it the same way you would control the hubble plus if theres ever a problem we know we can land on the moon safely.

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Safely and cheaply? That'd be good.

Control of stuff on the moon must be a nightmare. The signal takes a while to get here, and it's bad enough waiting for a 20 second frame to load when targeting something with K3CCD.

I think the best bang for the buck would be for me to find out how to steer the Hubble by changing the access codes and stuff. My own space telescope, now wouldn't that be cool?

Captain Chaos

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Just as CC alluded - space travel AIN'T SAFE and it SURE as h#ll AIN'T CHEAP (at least not using technology currently open to the public eye). FHT's (nice one Gaz :)) are easier at present to construct and site on earth. There are some great places to put them where the clouds tend to hang around somewhere down BELOW. If seeing ain't great then we use the image stabilising software and somesuch. Yeah, the drive to use the scope can be a bit of a foggy nightmare but we just leave that journey to Astroman. Then he can tell us how things went when he gets back to SGL 8)

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Boy, there are some good people in this forum! You guys make some great points here. Astronomers' lack of imagination will no doubt someday lead to an FHT in Chile or the Canary Islands or something. :) Mark Gaz' words!

HST is only a 2.5m mirror, but because it's in space, it doesn't need adaptive optics. (AO) AO works equally well at visible wavelengths. Not sure where you heard IR "only", Kong. ?

Speaking of Chile, it makes my 7" average ANNUAL rainfall look like a rainforest. Most of the clouds, even atop Mauna Kea occur BELOW the summit, so the seeing is simply amazing. Kitt Peak also has amazing seeing, and I myself have participated in data taken from a telescope larger than HST there.

The problems with operating a scope on the Moon are numerous. Expense and practicality are the biggest. Cost aside, some roadblocks you may not have thought of. 1) Batteries die, even after being solar charged. I know, I know, Spirit and Opportunity have lasted years instead of months, but that's partially due to wind blowing the dust off the solar panels. But the Moon rotates once every ~28 days, so 2 weeks in Sun, 2 weeks in dark makes for tough battery life. Plus, the current demands on a telescope are much higher than a robot. 2) The Moon is extremely bright when the Sun is on it. Infrared may be good, but visual, read "pretty Pictures" will be limited, and so will public interest, sad to say. 3) Even in the "dark", you've still got the pesky Earthshine lighting things up. 4) Aiming software would have to be radically altered. Not particularly difficult, but it just popped in there. :insects1: 5) The time for signals to travel to the Moon are only about 1 second, so that wouldn't really be a problem on a 3 hr exposure.

And those are just what measly little me can come up with. Micrometeorites, hard radiation and so on, I'll leave to the engineers.

Myself, I vote for an Earth based observatory as close to me as possible. MAybe I could get a job there? 8)

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Actually AM I read it in the astronomy now 2007 yearbook. There's an interview with Dr Matt Mountain, granted he's now the director of the Hubble science institute but he used to work in Hawaii on the Gemini scope and he said he ran an adaptive optics group there. He said just that, and also that AO wouldn't work for wide® field shots as the further the subject is from the reference star the worse the correction - you'd need multiple guidestars and fantastic computers. As an aside, I went back and bought the yearbook and i highly recommend it to others, there's also some other nice articles including one on mars.

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The problems with operating a scope on the Moon are numerous.

not to mention the possibility of a meteor hitting the mirror! :shock:

Andrew

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Actually, I did mention micrometeorites. :)

Well, I believe you, Kong. Apparently, my understanding of AO is incomplete, so I've sent an email to a friend of mine at the University of Arizona Mirror Labs for a clarification. As you know, they make giant mirrors there, as well as the flexible secondaries for AO systems, including the Large Binocular Telescope, (what an original concept name :lol:), nearing completion in Safford, AZ.

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Thanks AM! You indeed have friends in high places :), I'll be interested to know what he says. I the mean time a little googling came up with this http://cfao.ucolick.org/ao/limitations.php dated 2003, which just says the same but not really adding any details I can understand. This link http://www.eso.org/projects/aot/what_AO/ talks about needing many more deforming elements providing finer control of the bendy secondary, and much brighter reference stars; at visual wavelengths. Shorter wl's apparently jiggle a lot more in the atmosphere. Apparantly full visual AO IS in use by the US military for peeking at satellites. There's a lot of other stuff but it's way too much heavy maths for me.

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I heard back from my friend at U of A. He writes;

Steve!

I'm fine, hope you and Rosie are too.

I'm no expert, but I believe that the limitations in going to visible wavelengths is that you can't make a mirror that is infinitely deformable. It goes back to the "seeing cell" size - typically 10-30cm diameter (patch of air over which diffraction limit is obtained). When you image the primary onto the deformable mirror mirror, each actuator needs to similarly map down to the seeing cell. So with a 400cm mirror and 10cm seeing cells, you need a minimum of 40 actuators across the diameter and something like 1200 total for the deformable mirror. At least to this point, that hasn't been done (limitation is electronics and computer power). I think the LBT mirrors will have about 700 total for the 8.4 meter mirrors, only about 15 across the diameter corresponding to a seeing cell of 56cm - pretty good seeing would be needed. Since the seeing cell size is a function of wavelength (linear, I think) it is easier to get better seeing at 2 microns because seeing is naturally better and fewer actuators are needed. I don't know if this is the only reason, but is my understanding. If you google adaptive optics, you will find lots of explanations.

One of the most impressive displays I saw was a movie of Saturn's moon Titan occulting a pair of stars - the DISK of Titan filled half the screen, and as the star hit the atmosphere, it was refracted around the disk by different shells of the atmosphere - it never disappeared, just moved around the disk - was quite amazing!

Anyway, hope all is well - see you 'round!

Dean

What he means is, you can reduce bad seeing at visible wavelengths, but not by as much as infrared because the distortion is less, due to the longer wavelength.

I told him afterward, I may have been confused by a demonstration video I saw at Gemini North. It was computer generated, simulating the corrections sent to the deformable mirror, but didn't specify if it was visual or IR.

As always, of course, if you don't understand what he said, I'd be glad to clarify, if I can when I have time.

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Thanks AM. So visual is limited as the size of the 'seeing cell' gets smaller as wl shortens, so you'd need lots of actuators. In any case sounds like its a technical problem that'll gradually be solved (or already has been according to that ESO link). Cheers.

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