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100 Meter OWL Telescope Project
mindpixel writes: "The European South Observatory (my employer) is getting VERY serious about building the OWL (OverWhelmingly Large) 100 meter telescope. Check out this new site dedicated to the project. You can see some cool diagrams of what the OWL telescope will look like and some simulated images here." For more about telescopes of unusual size, you might read McKinstry's interview last year.
One thing which I've been wondering about VLT is the usage of just digital imaging (FORS1, etc)...or at least I haven't noticed any VLT cameras using traditional film (correct me if I'm wrong). I know that CCDs are great for making photometric measurements because of their linearity, but their resolution is nothing compared to large photographic plates used in older cameras. For example, FORS1 is just 2048x2048.
Well, ok, camera resolution might not be so important in most research, but I would imagine that doing the Palomar sky survey (hundreds of huge plates) with CCDs would be impossible (it would probably require trillions of pictures). ...And the best space poster pictures are still the ones taken with the Palomar 5m. ;-)
So, how are surveys made now or in future, with CCDs or plates? Are surveys or other hi-res imaging still relevant?
[I'm eagerly waiting for a job decision from ESO at Garching, should come next week. It would be great to get to mess up^H^H^H^H^H^H^Hdevelop the computer systems there. ;-)]
Not quite solid, try made of hexagonal mirrors approx 2m across. It would be a huge pain in the ass to make a 100m diameter mirror, not to mention uneconomic. Thats why they plan to have it tiled. But all the tiles do make up the mirror for one large telescope. Cheers
On a more serious note, why are we still building telescopes on Earth with the limitations we face on the ground? (Atmospheric distortion comes to mind... And I do understand they'll probably build this thing in a remote area to avoid the obvious: smog, city lights, etc. Still, though, there are some inherent limitations that they give a telescope like this by building it on and designing it for Earth.)
Many ground-based telescopes are using "Adaptive Optics" systems, where an optic module tries to reverse the atmospheric distortion. They are already quite successful for very small fields-of-view, and a next generation of instruments are under development for bigger fields. The OWL would be practically useless without adaptive optics. I personally attended a talk by ESO's director, where he said that the success of the AO modules in the next years will be the deciding factor for the OWL.
More awesome pics from space... If anyone doesn't know about astronomy pic of the day over at nasa... I highly recommend you go looking through the archives. Some of the pics from hubble and others are so aweing. http://antwrp.gsfc.nasa.gov/apod/astropix.html
I've recently seen a TV program about the building of the VLT. It showed the conception and the technical implications of the telescope. At one point they spoke of a device in charge of monitoring and correcting atmospheric optical aberrations, in real time.
With this correction the telescope is providing hyper clear pictures of the sky.
I've searched the ESO site and found a reference to this device on this page (scroll down to "Active Optics").
Besides, given the limitation of the size of objects that can launched in space, a telescope based on earth, big enough and judiciously placed, and equiped with this device, will always achieve better results than a space's one.
This doesn't apply to telescopes described in the article, but there's a method for removing the light of a star in order to see dimmer companions (such as planets) which is called nulling interferometry.
An interferometer is an instrument with two telescopes, which uses the wave nature of light to combine them. When you separate 2 telescopes by say 100 meters and combine their light properly, you get the apparent resolution of a 100m telescope (minus the light gathering power and the cost).
A nulling interferometer doesn't try to combine the wavelengths at the same place (think reinforcing the wave you're getting from the object). Instead it delays one of the the waves by 1/2 wavelength, so when the two are combined, they cancel each other out (at least in the center).
So the light of the star is "nullified" while you can still measure the light coming from very close by.
The technique has been demonstrated in the lab, but I don't believe it has been used in practice. It may be used in some astronomy satellites in the future.
Doug
Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
The problem is that angular resolutions of telescopes are given for separating two objects of the same maginitude. A star is so damn bright compared to any orbiting planet (probably more than 1,000,000,000 times brighter) that, if the image is taken with an exposure time that would make the planet visible, the atmosphere will spread the star to many arc secs, even with the best adaptive and active optics. I think OWL would also have this problem.
I don't know exactly why Hubble can't see such planets. Probably its angular resolution is still not good enough. Also, CCDs don't always behave nicely when they are grossly overexposed, as the CCD would be if there's a planet in one pixel and its star two pixels away.
Btw, Alpha Centauri is a multiple star, and the close component stars probably can't have stable planets. Proxima Centauri (one of the components) is farther away from the others and might have planets (I guess).
The Sloan Digital Sky Survey is using CCDs to map one quarter of the entire sky, in five passbands. Its main camera uses a mosaic of 30 2048x2048 CCDs to cover an area about 2.5 degrees across (although there are gaps between the chips). Other mosaic cameras have even more pixels.
Future ground-based surveys will use electronic detectors, not photographic plates. The increased sensitivity and linearity of electronic detectors, plus their inherent digital output, make them far superior to plates.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
Space based and ground based telescopes compliment each other. Right now, the Hubble's primary mission is that of a scout... it finds targets for the VLT (which I operate)... the Hubble's mirror is small and exposure times are limited by cosmic rays... the ground based VLT is much better at getting science data once the Hubble finds the target.
The next space telescope will be the NGST (Next Generation Space Telescope) which will be about the size of a single VLT telescope (we have 4 here in Chile) and it again will act as a scout for the OWL.