TMT thread

I want both. I want an array of OLT in space too.

With space telescopes you are not constrained about mass and you need no atmospheric compensation, and you get more UV.

knowing physishits, it's probably called the Totally Magnificent Telescope.

>With space telescopes you are not constrained about mass
Quite the opposite. The next generation ground based telescopes will weigh thousands of tonnes, the next generation space telescope (JWST) weighs 5 tonnes. If it doesn't fit on a rocket it isn't a space telescope.

>you need no atmospheric compensation
Which is very nice but ground based telescopes are larger because they are cheaper and so will have a higher angular resolution in cases were they can use AO. They're complimentary.

>you get more UV.
Which is excellent but only when someone builds a UV telescope. With JWST most of the visible is missing not just the UV. TMT will provide UV and visible capabilities that JWST lacks. WFIRST also won't do the UV or much of the visible. There is WSO-UV but it may never launch and even if it does it will be very similar to HST/COS in performance (assuming it performs as claimed).

>If it doesn't fit on a rocket it isn't a space telescope.
You could have origami style folding like JWST with higher complexity, or you could launch from the Moon or even base it on the Moon which means no problems with fuel and reaction wheels. With 1/6 of the gravity you could make huge telescopes.

>ground based telescopes are larger because they are cheaper
True. And what about sites? I hear Hawaii is getting rather hostile these days.

>TMT will provide UV and visible capabilities that JWST lacks.
How deep does that go? After all there is something called vacuum UV.

>You could have origami style folding like JWST with higher complexity
I was referring to the mass limitations, context.

>or you could launch from the Moon or even base it on the Moon which means no problems with fuel and reaction wheels. With 1/6 of the gravity you could make huge telescopes.
The Moon also has dust causing both mechanical problems and scattering light. The Moon also has huge temperature swings. A space telescope would be cheaper (as no requirement to land) and better. Reaction wheels an annoyance because they're mechanical and break down, a lunar telescope would also require a mechanical mount.

>True. And what about sites? I hear Hawaii is getting rather hostile these days.
Chile has better conditions anyway. The TMT site selection process ranked Cerro Armazones as the better site but it was cheaper to share infrastructure with Keck. One big difference is that Mauna Kea doesn't have particularly good weather, the fraction of clear nights on MK is 76%, on Armazones it was 89%. That's 17% more telescope time.

>How deep does that go?
You can get down to atmospheric cutoff at 300nm. It allows you to access the Lyman alpha forest at z~2 which is much more dense that lower redshift. Space UV astronomy is nice but there is going to be a massive gap after HST and COS is already running out of things to do. TMT and ELT will do extraordinary things at higher redshifts, lower redshifts will have to wait.

telescopes are a meme
>Lets look at shit we'll never get to within hundreds of years

Whats the f**king point

>what about sites?

Maybe French Polynesia or American Samoa or Kiritimati? Hell even Johnston Atoll would work I guess, but that might be a bit too close to the sea level for hurricane safety. Kiritimati is really low but is right in the sweet spot for no hurricanes. I think all of those have airports already.

You can't just put a telescope anywhere. Being an island is not important. You want a site which is high, dry, has very stable atmosphere, good weather and low light pollution. None of the places you mention will be suitable, most aren't high enough by a long way and the mountains in French Polynesia are too steep which causes turbulence.

Even Hawaii gets hurricanes.

It is more about human ingenuity than optimal location. The only thing those other sites lack is height and FP isn't all that bad.

Hurricanes aren't the problem, the weather issue is can you even open the dome for half the nights and what the seeing will be when you do.

>It is more about human ingenuity than optimal location.
No, that is complete bollocks. TMT spent years surveying sites. Putting a telescope in a third rate location throws away sensitivity you will never get back.

FP is not suitable in the slightest because of this. The peak isn't above the inversion layer. That means the clear weather fraction will be crap. The fact it is green at the top tells you the site is not dry which will destroy performance at longer wavelengths. It's also too steep which will mean poor seeing and there is no way to build a huge observatory up there.

You must be fun at parties. Control your nihilism kid.

You do recall that Hawaii is the best location right? You also recall that making anything additional there will most likely not happen right? We are amazingly lucky the vote went as well as it did for the TMT. The locals put up a good fight.

The locations listed in are all good for everything except height. Their weather is outstanding, just like Hawaii, though Christmas island (Kiritimati) has the best weather of them all.

Hell, light pollution is getting worse and worse at Hawaii and the other optimal sites around the world that have good weather and height.

>The locations listed in are all good for everything except height. Their weather is outstanding, just like Hawaii, though Christmas island (Kiritimati) has the best weather of them all.
Wouldn't the humidity be a problem?

Of course.

Imagine a 10km mirror telescope in space

Isn't that well well beyond the limit of angular resolution for an optical telescope even with adaptive optics? Pretty much everyone is sticking to 10m aperture or less even as an array for an astronomical interferometer.

it most likely is, but it would probably work if the mirror could be manufactured and placed in space along with the rest of the equipment
I wonder what the numbers on a telescope like that would look like

>imagine if FAST was optical

It'd end up being a massive array of segmented mirrors. There'd also be tons of different apertures. Something that large would be better used as a radio telescope. Though, if you are going to make a space radio telescope, you may as well make it 100,000k+ in size for full ELF range too. But, you'd need it outside the Heliosphere for it to be any good.

>You do recall that Hawaii is the best location right?
Wrong. Read the site selection papers.

arxiv.org/abs/0904.1183
adsabs.harvard.edu/abs/2008SPIE.7012E..1XS

>The locations listed in are all good for everything except height.
Height not a small problem, that's enough to completely ignore them. Without height the seeing is terrible, the precipitable water vapor will be high and the clear fraction will be bad. All of those things just throw away performance. If it's not above the inversion layer it isn't worth considering. On tiny islands there will also be salt off the sea which will degrade performance further.

>Their weather is outstanding, just like Hawaii, though Christmas island (Kiritimati) has the best weather of them all.
What astronomers call good weather is not what other people call good weather. Mauna Kea actually has mediocre weather as I pointed out. The clear fraction is just 76% compared to some Chilean sites which are 85-90%. Christmas island is also nowhere near high enough.

Site selection is a science, you don't just guess place names.

>Hell, light pollution is getting worse and worse at Hawaii and the other optimal sites around the world that have good weather and height.
Chile has reserves for Paranal and now ELT.

Sure thing, kid.

No need to cry over the fact someone on this board knows what they're talking about.

>overwhelmingly large telescope
These names never fail to make me smile

>Isn't that well well beyond the limit of angular resolution for an optical telescope even with adaptive optics?
There is no upper limit, if you build a bigger telescope the diffraction limit is smaller.

>Pretty much everyone is sticking to 10m aperture or less even as an array for an astronomical interferometer.
That's just because the largest telescope today is 10 meters, it's not some fundamental limitation.

It's sad really. It would have been able to measure redshift drift, a direct measure of the expansion of the universe in real time over a decade. ELT might be able to but probably not and if it does it will take decades.

>direct measure of the expansion of the universe in real time over a decade

Stop user. I can only get so erect.

Is there something like Moore's Law but for telescope diameters?

Sort of but there's a lot of scatter. I can't find the original plot but this is one. It's only really plotting the next largest telescope (plus the notable VLT and Gemini).

Once it gets so large, there's no point since it doesn't aid anything.

en.wikipedia.org/wiki/Diffraction-limited_system

Nope. The diffraction limit is set by the wavelength and the telescope diameter. Build a bigger telescope and the maximum resolution increases. The diffraction limits sets a maximum angular resolution for a given telescope, not the maximum of any arbitrary large telescope.

en.wikipedia.org/wiki/Angular_resolution#Explanation

Secondly larger telescopes even when not diffraction limited improves the sensitivity.

How long until we have telescopes good enough that we get to start naming mountains on a planet orbiting a distant star?

Tuesday, 978 weeks from today

It's funny because cinnamon is complete garbage.

TINY AMERICAN TELESCOPES

Atacama desert is the best place on Earth. Other places are only valid in order to see other patches of the sky not visible from Atacama.

>Atacama desert is the best place on Earth.

Except for the anarchist bombings. A telescope would be a prime target.

but that one is going to be built on the American continent

Moon telescope when?

Never, because it's stupid

1600: 1 E-3
2000: 1 E+2

So we have very roughly 5 orders of magnitude in 400 years, or close enough to one order of magnitude per century.

Telescopes are already there and yet, nothing. Observatories have security. There have been observatories in Chile for half a century. They survived the coup, they survived the junta, they are doing just fine.

So, like what happens if every one of those massive telescopes on the same side of t he planet, decides to look at the same object in space then link themselves together for AO purposes?

Nothing special. Adaptive Optics is used to correct for the blurring of images due to turbulence, it isn't used to link telescopes together. You cannot simply combine the data from different optical telescopes and get very high resolution, it is not like radio where the phase information is recorded. Optical telescopes must be linked physically with an optical fibre or light relays to do interferometry, it is not practical beyond a few kilometres.

By Europeans. And thankfully Chile doesn't have entitled natives declaring every piece of dirt sacred.

Fucking 10/10 user, good job

AO is specifically used to link segmented mirrors together to compensate for changes in the frame that holds everything together. It does that on the nanometer scale. The only problem with doing that around the world is time lag.

>AO is specifically used to link segmented mirrors together

No it's not. Lots of non-segmented telescopes have AO.

eso.org/sci/facilities/develop/ao/sys/galacsi.html

>to compensate for changes in the frame that holds everything together.

You're thinking of Active Optics, not Adaptive Optics, the later is called AO. Active optics cannot be used to link different telescopes, all it consisted of is actuators behind the primary which push it back into shape. Note that correcting the shape of the primary mirror has nothing to do with lining different telescopes.

>The only problem with doing that around the world is time lag.
No, as I said interferometry at optical wavelengths requires physically recombining the light. Adaptive and active optics have nothing to do with linking different telescopes together.

Sure thing, kid.

t. adult

TMT stands for Thirty Meter Telescope, because it's a 30-meter telescope and who needs clever names.

I didn't love Cinnamon Toast Crunch when I was a kid because it got soggy too fast.

I eat fast as an adult and I use much less milk. It's in my top 5 favorite cereals. It's also the best to eat dry, IMO.

I tried cinnamon cereal once, the taste was so strong that I got a headache, hate cinnamon since.

Except when I eat seminola pudding or rice pudding with some sugar and cinnamon because I use very moderate amounts.