Powerful Optical Telescope Captures First Binocular Images

The Large Binocular Telescope consists of two 8.4-meter mirrors which function in tandem to provide resolution greater than that of the Hubble Telescope. The LBT's first "binocular" images were captured recently, marking the end to a long and laborious construction process. We previously discussed the LBT when images were captured from the first mirror to be installed. Quoting: "The LBT ... will combine light to produce the image sharpness equivalent to a single 22.8-meter (75-foot) telescope. 'To have a fully functioning binocular telescope is not only a time for celebration here at LBT, but also for the entire astronomy community,' UA Steward Observatory Director, Regents' Professor and LBT Corp. President Peter A. Strittmatter said. 'The images that this telescope will produce will be like none seen before. The power and clarity of this machine is in a class of its own. It will provide unmatched ability to peer into history, seeing the birth of the universe.'"

Comments

This might be a stupid question...

[TubeSteak]

If two telescopes are good, wouldn't three be even better?
It's not like two is some arbitrary limit... right?

Re:This might be a stupid question...

[hey!]

IANAA, but I think the advantage of the binocular telesecope is resolving power, not light gathering power.

With conventional telescopes, a bigger telescope doesn't just "see" dim objects; it sees objects that are closer to each other (that is they have a small angular separation in the sky) than smaller telescope. So generally, bigger is better. The problem is that the difficulty of making precise optical components goes up very rapidly in size. The 200 inch Pyrex blank used to make the Hale telescope at Mt. Palomar weighed 40,000 pounds, and took a year to cool after it was cast. Naturally, it had to be figured to optical perfection, a process that took many years, and involved removing 10,000 lb of glass.

The idea here, I think, is to get the resolving power of a very large disk without the engineering complexities and cost. You do that but taking two largish but not heroically large mirrors, placing them 75' apart; then you carefully combine the light from each mirror to get the resolving power of a 75' mirror. This last process is tricky, but nothing compared to casting a 75' mirror, which would be over eight times the diameter and thus 64x the weight. It would take decades to create the blank, much less grid it.

I suppose you could add more mirrors than two, and there might be some advantages, but the chief advantage of the binocular arrangement is to get more resolving power for less (net) engineering cost. Since doing this kind of thing on this kind of scale is novel, and it's always a kind of bet when you do something new. Probably the best bet was to make two mirrors as large as you can afford then connect them in the simplest possible way that does the job, which rules out more mirrors.

For years, the U of Arizona had a telescope that combined the light from six 1.5m mirrors to make the equivalent of a single 4.5m telescope, so I suppose it's possible to use even more mirrors than two. The MMT arrangement was upgraded a few years ago to a single 6.5m primary mirror constructed from a hollow honeycomb matrix rather than a single massive Pyrex blank, and they recently added an adaptive optics secondary to improve the practical resolution of the telescope, so there's still some room to improve "conventional" ground based telescopes.

It's easy to imagine that in this century we'll see astronomical instruments an order of magnitude better than any currently in existence.

Doesn't seem that large.

[wozzinator]

I go to school there and surprisingly enough the building that holds it is relatively small in comparison to other telescopes. I dono how they do it!

Re:That's quite right - And the future of astronom

[a_claudiu]

It's almost the same with microprocessors. Are the multi core better than a very quick single core (e.g. 2x2Ghz vs 4 Ghz)?

In the case of telescopes how big can you make a mirror without imperfections and tolerant to temperature changes? And then are coming the logistic problems.

For multiple telescopes you can enhance the image, compensate for defects in individual mirrors or atmospheric distortions but in absolute terms you'll obtain a better image from a single telescope with the equivalent mirror surface. There are other problems as well but these are the first coming in mind.

Is that a supernova?

[dsvilko2]

If you compare this NGC2770 image with the one taken by SDSS (Google Earth), one star is clearly missing on the SDSS image (the brightest one). That would certainly explain the choice of the target but there is no mention on the linked article. Anyway, I expected a larger difference in resolution between the image taken by a 2.5m wide-angle telescope (SDSS) and a 2x8.4m binocular telescope.

What are the advantages of a binocular telescope?

[TropicalCoder]

This was my question when I read the FA. Like another respondent, I thought that with the stars so far away there wouldn't even be any parallax. I decided to ask my friend Google what are the advantages of a binocular telescope and found this...

"So what does it feel like to actually use a large aperture binocular telescope? David gives us his account; Mind blowing is probably the phrase that springs to mind..."

"The incredible sense of total immersion in the reality of the experience is what binoculars are all about. It's astronomy at another level. Seeing the large globular cluster Omega Centauri for the first time almost made me fall backwards off the step. The depth and resolving power on this object is spellbinding. Moving just outside the field of view of this object and panning slowly towards it, you're firstly presented with a pitch black sky with a scattering of random stars. As you move onto the object your eyes and senses are completely overwhelmed. You can look deeper and deeper inside this cluster and there is always more to see. It feels as though I've arrived on the doorstep to this cluster in my spaceship."

"A definite three-dimensional feeling is present, the objects appear to float almost in front of you, even though this is obviously not possible due to the enormous distance of these objects. One explanation is an effect called chromatic stereopsis, which due to chromatic aberrations in your eyes makes the red and blue stars focus at slightly different distances. Simple things, like double stars that have never captured my imagination are suddenly transformed into objects worth gazing at. Smaller and much fainter globular clusters all benefited from the relaxing view using two eyes. The fainter globular clusters if viewed with only one eye, needed averted version to make them visible, however with both eyes open, they were blatantly obvious."

This amateur astronomer with a binocular 16" telescope concludes after 6 months of constant use: "So far I have not found any category of object to observe that does not benefit greatly from the advantages of a true binocular telescope."