ESO's Very Large Telescope Now Delivers Images Sharper Than Hubble (eso.org)

ffkom shares an excerpt from a press release via the European Southern Observatory: ESO's Very Large Telescope (VLT) has achieved first light with a new adaptive optics mode called laser tomography -- and has captured remarkably sharp test images of the planet Neptune, star clusters and other objects. The pioneering MUSE instrument in Narrow-Field Mode, working with the GALACSI adaptive optics module, can now use this new technique to correct for turbulence at different altitudes in the atmosphere. It is now possible to capture images from the ground at visible wavelengths that are sharper than those from the NASA/ESA Hubble Space Telescope. The combination of exquisite image sharpness and the spectroscopic capabilities of MUSE will enable astronomers to study the properties of astronomical objects in much greater detail than was possible before.

Comments

Re:Aim it at the moon...

[Anonymous Coward]

[1] MUSE and GALACSI in Wide-Field Mode already provides a correction over a 1.0-arcminute-wide field of view, with pixels 0.2 by 0.2 arcseconds in size. This new Narrow-Field Mode from GALACSI covers a much smaller 7.5-arcsecond field of view, but with much smaller pixels just 0.025 by 0.025 arcseconds to fully exploit the exquisite resolution.

tan( 0.025 arcseconds ) = 1.2120342e-7
distance to the moon is 384.4 million meters

1.2120342e-7 * 384.4e6 = 46.59 meters

tl;dr: Still about 2 orders of magnitude away from being able to take a blurry ass 15x20 pixel image of the lander. Try again in a few decades.

Re:Slashdot, please help clean up Slashdot

[Joce640k]

Please Slashdot, can you stop all these trolls from polluting the Slashdot space. In the past the comments by users were of an interesting nature related to the subject story, but now on 5% maybe is about the story as trolls post rubbish about Politics, Defamation, Racist and such other crap....yada yada

You see that sliding bar thing at the top of the screen? Yeah, that one...

Hubble optical flaw origin

[sjbe]

IIRC the mirror was ground with gravity present. Then under zero G conditions it sprung back to an unanticipated shape.

Your recollection is incorrect. It was ground very precisely to the wrong shape due to some incorrectly assembled testing equipment. The problem was actually noted prior to launch but the test results were ignored. Gravity or the lack thereof had no relationship to the problem with the shape of the mirror. It was simply made to the wrong specifications and then final testing failed to catch the problem.

Re:Hubble optical flaw origin

[crunchygranola]

Also, you could test for the effects of gravity by turning it upside-down. If the mirror was still the right shape, then gravity is not an issue.

Ah, grasshopper. You fall for the very reasonable assumption that the Hubble was flown with an incorrectly figured mirror because no one on the ground could test it properly and find out that this was the case.

That isn't what happened.

When the mis-figuring was discovered by NASA, in orbit, I too was stunned. How could the engineers have relied on just one test to verify it?

They didn't.

The mirror was over-budget, and behind schedule, and management at Perkin-Elmer wanted to ship it. The mis-assembled instrument was the contractually agreed method of mirror acceptance, and the one used in the figuring process. When engineers found after the figuring that simple tests showed that it was incorrect, P-E management didn't care, and didn't tell NASA.

There were people at P-E who knew perfectly well that the mirror would not work. But hey, the managers probably got bonuses when the mirror left the facility.

Re:Don't over minimize

[ceoyoyo]

The diffraction limit is not due to atmospheric effects. It is a fundamental limit imposed by the aperture of your telescope, which is more or less the size of the primary mirror.

It's currently easier to make a large aperture telescope on the ground, but with the bigger ones it's hard to achieve the diffraction limit because of atmospheric effects. The very best adaptive optics only get you to Hubble territory. JWST is bigger than Hubble.

Interferometry, particularly image-forming interferometry, is probably easier in space. You've got all the space you could possibly want, you can use free space lasers instead of fibre optics, and you can arrange for your telescopes to move easily to produce the image; on the surface you need to put them on train tracks.

Technically, big mirrors are easier in space too, since they don't have to support themselves against gravity. The current problem is you have to get them up there.

Re:One quibble

[Raenex]

But seriously - if you are going to claim that your earth based adaptive optics system will deliver sharper images than Hubble - show us a comparison.

Try reading the article:

https://www.eso.org/public/uni...

Re:Aim it at the moon...

[Solandri]

A 15x20 pixel image of the Apollo lander (about 9 meters wide) would require an image resolution of 0.5 meters.

• arctan( 0.5 meters / 384.4 million meters ) = 0.00000000013 radians, or 0.00027 arc-seconds

The Rayleigh criterion then tells us that to resolve something that small using blue light (shortest wavelength) would require telescope optics that are:

• 1.22 * (450 nm) / ( 0.00000000013 radians) = 4.22 kilometers wide.

You might be able to do it with an interferometer. This is done all the time with radio telescopes - each dish acts as a single point on a very large mirror aimed at the same spot in the sky. But an interferometer needs to be aligned within a quarter wavelength of the light you're using. Relatively easy with radio waves, not so much with visible light.

Anyhow, this is all a moot point. The Apollo missions left retroreflectors on the landing sites. These are mirror arrays which will reflect light back exactly 180 degrees. Scientists use them all the time to precisely measure the distance to the moon, thus proving that we've actually been there.