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Hubble Accuracy Surpassed By Earthbound Telescope
randuev writes "A high-speed adaptive optics system helped the Large Binocular Telescope (on Earth) to beat the accuracy of the Hubble Space Telescope's observations. 'A special sensor detects atmospheric distortions in real time and controls the mirror to adjust its position to compensate, effectively canceling out the blurring. The mirror can make adjustments every one-thousandth of a second, with accuracy to better than ten nanometers.' Now, that's what I call real-time. This nifty trick multiplied the Strehl ratio (optical quality) of the LBT by about 80 times. The new system was tested in May and June, so hopefully we'll soon see more space around us in higher resolution on Google Sky."
While this does mean that it could possibly make some Deep Field images. There is still another problem that makes this possibly intractable. The atmospheric absorption of some wavelengths means that it might still not be able to see certain areas in the spectrum effectively; this could prevent it from being able to produce nice deep field images like the hubble. However this ability to resolve objects that much better means that it could most certainly be effective at searching for planets.
Alas, there's no way around the Rayleigh criterion: http://en.wikipedia.org/wiki/Angular_resolution
We're not going to construct one-hundred-kilometer size telescopes any time soon.
It's great that atmospheric distortion can be largely eliminated, but just wait until we get some improved optics into space. Hubble has produced wonderful images, but the James Webb Space Telescope is going to be a phenomenal upgrade.
...that it was more than 20 years ahead of any Earth-bound telescope when it launched.
Probably not. It's not that the binary telescope isn't capable of doing Deep Field work, but the deepest of the deep imaging shots took Hubble keeping its optics focused on a single, apparently dark area of the sky for literally months. Deepest sky search took up most of the Hubble's lifespan during the last few years, and many other projects had to be put on the back burner. Administering big science involves trying to share time fairly for many projects, and I'd bet that many of the first time slots scheduled on the new version of the binary array are promised to the people who were bumped from the Hubble when it became apparent it was a good tool to investigate the very early universe. Other time is doubtless already reserved for those non-cosmologists who want to do other important astronomical things, such as exoplanet searches and resolving what's possible in visible wavelengths of our own galactic core. There's also a need sometimes to do visual backup observation when the orbiting infra-red or x-ray scopes find something unexpected in their wavelengths, and how much time could be borrowed or traded around for this depends on just how weird the other observations are.
Who is John Cabal?
Oh, there is a crazy way around it : http://www.spaceroutes.com/astrocon/AstroconVTalks/Maccone-AstroconV.pdf
: using the sun as a gravitational lens. Sure, it need a spacecraft to go 13x times farther than any spacecraft ever did, but we would get gorgeous pictures. Some people say this may be our only way to ever observe directly exo-planets in details. I am not sure if it enters in the "practical within my lifetime constraint" but if you have 50 more years to go, I wouldn't rule it out.
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
The amount of light collected is proportional to the area of the mirrors times the transmissivity of the atmosphere.The LST has about 20 times the light gathering area, so it can outperform the Hubble when using its adaptive optics. The mitigating factor in the LST's usefulness is that the atmosphere absorbs certain spectral components.
The determined Real Programmer can write Fortran programs in any language.
There are several limitations to adaptive optics, which are by no means a cutting edge technology for large observatories any more. Just about every telescope being built or upgraded today are having adaptive optics fitted.
One major limitation is that the adaptive optics are only good for small fields of view since you're using a single guide star to calibrate the disturbances in the atmosphere you're correcting. So they are not good for imaging multiple objects or even large single objects (like a single galaxy). Another is that since you're not in orbit like Hubble you have to wait for the planet to rotate, so a deep field would take much longer anyway.
When we lose Hubble we lose some unique capability. Even successor telescopes that don't work in optical light will not fill that void. Adaptive optics will only be useful in some circumstances whereas Hubble would have been useful in the general case. Oversimplifications like this story don't belong on a techy site like slashdot.
These posts express my own personal views, not those of my employer
Accuracy is too vague a term to use when describing a telescope.
The adaptive optics increases the resolution of the telescope by eliminating the refractive errors caused by atmospheric turbulence. And the basic resolution of the LBT is better because its 8.4m mirrors are over 3 times the diameter of the 2.4m Hubble mirror.
The ideal would be a larger mirror in space, such as the James Webb telescope is to be if it works.
[Disclaimer: I eat lunch with LBT engineers, so I know way too much about the gory details of getting 600 magnetic actuators to work together without breaking glass.]
The determined Real Programmer can write Fortran programs in any language.
http://torcache.com/torrent/DA4B118239E5BC4DF4ACF591D1077AAEC1C4D61B.torrent National Geographic documentary that came out recently about it.
There's always complexity behind these stories, and it might be interesting for everyone to understand why this development, although a great and useful accomplishment, is not equally useful for all types of astronomy:
Much of astronomy is being pushed by the need to image deeply in the infrared. For example, to discover the most distant objects in the universe, you need to use near- and mid-infrared wavelengths (because objects that are far away are receeding rapidly, hence redshifted). And for this, mostly what you want is raw photon count, not sharpness (although that would be a "nice-to-have" someday).
Unfortunately (for astronomy), the atmosphere absorbs heavily in the infrared wavelengths (aside from a few windows, which give us our passpands), and as a result, a 1 meter telescope in space still beats an 8 meter on the ground, in almost every respect (putting cost aside for a moment...).
At least for infrared work...