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Engineering the 30-Meter Telescope
yyzmcleod writes "When completed in 2018, the Thirty Meter Telescope (TMT) will be the world's largest and most powerful, with a resolving power 100 times that of Hubble. As TMT's preliminary design review nears, this article details how its enclosure, segmented mirror and adaptive optics will work to let astronomers peer back to the beginning of the Cosmos."
I was hoping for the Thirty Meter Nano-Telescope (TMNT)
Correct link without the 501 error: http://www.canadianmanufacturing.com/designengineering/features/industryfocus/article.jsp?content=20090512_125904_8252
"World's largest and most powerful".
Yeah, except for the 42-m E-ELT, also slated for 2018-ish. And that's still excluding radio telescopes...
2018 !, I wanted to use the 30 meter telescope to fry ants in other galaxies now !, or maybe see some boobs.
R.Morton
modded quote "what's that he's talking about? Windows , Never had a problem with Windows till I tried to use it."
As the actual article notes on its first page, TMT will have roughly 100 times the collecting area of Hubble: this goes as the square of the diameter of the telescope, so with TMT = 30m and Hubble = 2.5m, that's about right.
Resolving power (if the TMT can be made diffraction-limited, which it is aiming to do, but which is hard nevertheless) gets better linearly with the diameter, so TMT will have roughly 10 times the resolving power of Hubble.
The more appropriate space-based comparison in 2018 will be JWST which has a diameter of 6.5m, although JWST and ground-based ELTs are more properly thought of as being complementary, not competitive: they do different things.
But as already noted, the more appropriate comparison is with the European E-ELT which is under Phase B study now and is baselined for 42m diameter.
More interesting is where the TMT and E-ELT will be located: same hemisphere or not? Current bets are on E-ELT being in Chile, with TMT possibly going to Mauna Kea. This would be a better outcome for us astronomers than having both in the south, IMHO.
As I said, ground- and space-based telescopes are actually highly complementary: it sounds greedy, but we really need both.
Space has the advantage of there being no atmosphere to block some of the incoming light and blur the image. Also, if you cool your telescope down (e.g. ESA's Herschel being launched tomorrow and NASA/ESA/CSA JWST in 2014), then you benefit from greatly reduced sky background at infrared wavelengths. This can result in an enormous increase in sensitivity in situations where the background matters, e.g. imaging of extremely faint sources.
Also, space-based telescopes can cover a wider wavelength range, including wavelengths that don't make it through the atmosphere, so some kinds of thing must be done from space (e.g. X-ray astronomy as in NASA's Chandra and ESA's XMM-Newton).
At the same time, space telescopes are much smaller than state-of-the-art ground-based ones, and thus the ground-based telescopes can catch many more photons over all. For some science (e.g. medium- to high-resolution spectroscopy of extremely faint objects where the background doesn't matter), it's all about the number of photons you can collect.
Also, if you can implement adaptive optics on your ground-based telescope, you can get higher resolution than in space.
As an example of true synergy, look at the many studies done jointly by HST and the ground-based 8-10m telescopes like the VLT, Keck, Gemini, and so on. In many cases, both were needed to complete the study.
Indeed, there are many of us helping develop both JWST and ground-based ELTs like E-ELT and TMT for exactly the same reason: we need both to get a more complete picture of what's going on out there.
Something gives me the feeling E-ELT will give us the ultimate answer about our universe.
One that hath name thou can not otter
1 'tube sag' only applies to telescopes which HAVE a long tube, that is, long focal-length refracting telescopes which have a lens at the front end, not reflectors, which have a mirror at the back end.
2 almost all large telescopes do not use any sort of 'tube' at all for supporting the optics, any solid tube would be too heavy to be useable, they use open-frame supports
3 'detail'....if by this you mean 'angular resolution' then no, a 6" telescope can NEVER beat a 24" one, the angular resolution [THETA] is determined by the equation sin THETA = 1.22 X [wavelength of light] / [telescope diameter], so a 24" scope will *always* have 4 times better (ie smaller) angular resolution than a 6" does.
4 even with this taken into consideration, large observatory-class telescopes are made large for their light-gathering capabilities, which allow them to see extremely faint objects, -not- for their angular resolution, which is limited not by the telescope design but by atmospheric seeing conditions, these fall far below the theoretical limit of a large telescope.
5. The 30m scope is not a Cassegrain, it's a Ritchey-Chretiene, same design as used in many other large and very successful observatories, and trust me, the people who build observatory-grade optics are very able to construct ANY shape of mirror they are asked to without mucking it up. Perhaps you're thinking of -amateur- telescope makers having a go at grinding a Schmidt-Cassegrain corrector plate in their garage/shed/back room using a grinding-rig they made out of broom-handles and a washing machine motor?
Your father may well be an optical designer and astronomer, you're not though.
Not trying to be nasty, it's just that nearly everything you wrote is either wrong, misleading, or half-right but mis-applied, and to the wrong thing.