Magellan II's Adaptive Optics Top Hubble's Resolution

muon-catalyzed writes "The incredible 'first light' images captured by the new adaptive optics system called Magellan|AO for "Magellan Adaptive Optics" in the Magellan II 6.5-meter telescope are at least twice as sharp in the visible light spectrum as those from the NASA's Hubble Space Telescope. 'We can, for the first time, make long-exposure images that resolve objects just 0.02 arcseconds across — the equivalent of a dime viewed from more than a hundred miles away,' said Laird Close (University of Arizona), the project's principal scientist. The 6.5-meter Magellan telescopes in the high desert of Chile were widely considered to be the best natural imaging telescopes in the world and this new technology upgraded them to the whole new level. With its 21-foot diameter mirror, the Magellan telescope is much larger than Hubble with its 8-foot mirror. Until now, Hubble always produced the best visible light images, since even large ground-based telescope with complex adaptive optics imaging cameras could only make blurry images in visible light. The core of the new optics system, the so-called Adaptive Secondary Mirror (ASM) that can change its shape at 585 points on its surface 1,000 times each second, counteracts the blurring effects of the atmosphere."

Comments

Still can't handle proper units?

[Russ1642]

Right in the summary we have a comparison between the 6.5 m Magellan telescope and the 8 ft Hubble.

Re:Still can't handle proper units?

[Anonymous Coward]

Well, the sentence where they compare the two is already converted to similar units, so it doesn't hurt my brain. YMMV

Re:Still can't handle proper units?

[hedwards]

The whole point of using Imperial units is that we don't want to throw out trillions of dollars worth of infrastructure to make the Europeans happy. Seriously, spend a year in the US with our measures and spend a year somewhere that uses metric measures; metric isn't any easier for any thing you're likely to be doing on a day to day basis. Unless of course you're a scientist or engineer.

Re:Still can't handle proper units?

[JWW]

Yes, the units for analogies are human hair, grain of sand, breadbox, car, football field, and internet.

Re:Still can't handle proper units?

[hedwards]

I love how the pro-Metric people mod me down, rather than posing a substantive reason for doing it.

I know the metric system, I've used the metric system and it contributes absolutely nothing in daily living. None of the conversions that it's optimized for occur in daily living with any regularity, whereas I regularly need half of something or 2x as much of it.

Re:Still can't handle proper units?

[krlynch]

Why? We switch units all the time, even when doing this "science" thing that so many seem to think only uses SI: eV, barn, torr, atm, etc. Suck it up, and learn to do conversions....

Re:Still can't handle proper units?

[Thud457]

actually, you're using the old, pre-normalization units. I has been scientifically proven that all units are convertible to Libraries of Congress.

1 Library of Congress = 25 Petabytes (data)
1 Library of Congress = 65,000,000 kilograms (mass)
1 Library of Congress = 30,000,000 m^3 (volume)
1 Library of Congress = 9,000,000 m of shelves (length)
1 Library of Congress = 53,700,000,000 BTU when burnt (energy)
1 Library of Congress = 11e10 seconds to read (time)
1 Library of Congress = 1,137 employees.
...

Re:Still can't handle proper units?

[jeremyp]

The whole point of using Imperial units is that we don't want to throw out trillions of dollars worth of infrastructure to make the Europeans happy. Seriously, spend a year in the US with our measures and spend a year somewhere that uses metric measures; metric isn't any easier for any thing you're likely to be doing on a day to day basis. Unless of course you're a scientist or engineer.

(my bold)

This is a story about science and engineering.

Re:Nice Summary

[Cryacin]

I suspect it will take a bit more than coffee.

Oh, wow. What you learn when you RTFA...

[philovivero]

As to the above drama about mixing measuring units, the article says:

These images are also at least twice as sharp as what the Hubble Space Telescope (HST) can make because the 6.5m Magellan telescope is much larger than the 2.4m HST.

So there you go. Both measurements in Imperial European Units.

But then I read on, and was pretty stoked to see them discovering things like this.

MagAO was then used to map out all the positions of the brightest nearby Orion Trapezium cluster stars and was able to detect very small motions compared to older LBT data, a result of the stars slowly revolving around each other. Indeed, a small group of stars called Theta 1 Ori B1-B4 was proved to be likely a bound “mini-cluster” of stars that will likely eject the lowest mass star in the near future (see figure 4). This result has just been published in the Astrophysical Journal.

Nice! I'd love to see a time-lapse video over the course of the next million years watching this black sheep star get flung out of its little flock.

Not entirely fair comparison

[girlintraining]

Hubble was sent into space with a major glitch in its primary mirror. While yes, we were able to give it, achem, corrective lenses for its near-sightedness, it was never able to perform to original specifications. This project, by comparison... doesn't have a defect in one of its most important components. So I don't know if this is an entirely fair comparison to make...

The fact is, they solve problems in two separate ways -- Hubble is a direct observation. There's no distortion, the light is the original and it's not smeared by atmospheric effect. Adaptive optics are amazing, but they're still additive in nature; You can photoshop, cut, and paste, but it'll never be quite as accurate as direct observation can be. That said, quite a lot can be done with it, and its a welcome addition especially in the age of limited scientific budgets for astronomy! I guess all I'm trying to say is... it's supplimentary, it is not a replacement for the kind of work Hubble did. We still need a replacement Hubble (obviously... with updated tech) for some observations.

Re:Not entirely fair comparison

[timeOday]

it was never able to perform to original specifications.

I thought the 2008 upgrade made it better than originally designed?

With its new instruments, Hubble will be 90 times as powerful as it was supposed to be when first launched - it will be like having 90 of the original Hubble Space Telescopes, astronomers say. The improvement comes from a combination of increased sensitivity and wider fields of view, allowing Hubble to see 900 galaxies where its original instruments would have revealed only 10. HST will be about 60% more powerful than it was right after the third servicing mission, before ACS and STIS failed.

Hubble resolution, at a price

[simonbp]

What they rarely mention in these sorts of press releases (everyone with AO system has a "better than Hubble" press release) is that the cost of getting to that resolution is losing most of the light along the way. It's not hard to beat HST with perfect atmospheric correction, as Hubble is only a 2.4 m aperture, and nearly every AO system is on a larger telescope. It's just that the correction is achieved by sufficient optical contortions that only a small fraction of the original light actually makes it to the detector.

My personal experience is that even the largest and most sensitive AO system in the world (NIRC II on Keck II with laser guide star) still really struggles make an observation in 20 minutes that Hubble can do in 5 minutes. If anyone were to launch a >3 m aperture visual-band space telescope (NOT JWST, that's IR), it would blow all these AO systems out of the water.

Re:Hubble resolution, at a price

[wonkey_monkey]

It's just that the correction is achieved by sufficient optical contortions that only a small fraction of the original light actually makes it to the detector.

Got any numbers on that "small fraction"? Is most of it lost through the atmosphere, or inside the optics?

Re:Hubble resolution, at a price

[Arkh89]

Surface times Integration time...
Keck : 10m^2 and 30 minutes (yes, no need to count the pi/4 ratio as we will make a ratio out of it)
Hubble : 2.4m^2 and 5 minutes.
Ratio : approx. 1%

What about the spectral range between the two?

Re:Hubble resolution, at a price

[Kjella]

My personal experience is that even the largest and most sensitive AO system in the world (NIRC II on Keck II with laser guide star) still really struggles make an observation in 20 minutes that Hubble can do in 5 minutes. If anyone were to launch a >3 m aperture visual-band space telescope (NOT JWST, that's IR), it would blow all these AO systems out of the water.

Yes, but "Hubble resolution, at a price" makes it sound like Hubble was the expensive one.

From its original total cost estimate of about US$400 million, the telescope had by now cost over $2.5 billion to construct. Hubble's cumulative costs up to this day are estimated to be several times higher still, roughly US$10 billion as of 2010.

Compared to that, the Magellan telescopes

Total annual costs $10,437,639

That figure is including amortization of the $73 million dollar ($3,665,250*20) investment so $200 million total over 20 years. This means you can get 50 AOs for the cost of one Hubble, now which one comes "at a price" again?

Re:Hubble resolution, at a price

[simonbp]

Inside the optics. For optical/near-IR astronomy (i.e. roughly in the wavelengths that your eyes can see), atmospheric opacity only comes into play if there are clouds. You always want to look at objects higher in the sky (meaning through less atmosphere), but that's more because they have less distortion.

Inside the telescope, you lose some light every time you have a reflective surface. A simple telescope might have three reflective surfaces at 0.9 reflectivity, and so no more 3/4 of the original light reaches the detector. A complex AO system typically has closer to ten mirrors, so no more than a third of the original light will reach the detector. And that's before you account for all the other losses, like scattered light and the parts of the distortion that deformable mirror in the AO system can't correct for. So at worst case, it might be only 10% of the original light making it to the detector.

AO systems are great, especially for bright targets, but it always makes me cringe when people claim they are "better than Hubble". Space telescopes exist for reason...

Re:Hubble resolution, at a price

[dywolf]

pretty sure the "price" he's referring to isn't monetary.

Re:Hubble resolution, at a price

[Shag]

Reflectivity is also going to be affected by what wavelength they're observing at. Typically, AO is used for near-IR observations. Although I forget the exact figures, I know Gemini North uses silver to coat its primary now because it only absorbs something like 1/4 as much NIR as aluminum did. /Former aircraft spotter for the AO lasers at GN and Keck

Re:Awesome

[AlecC]

It wouldn't need adaptive optics. Those correct for atmospheric aberration, and the moon doesn't have any atmosphere.

However, I don't see the point of lunar rather than orbiting. Lunar has gravity, which must be compensated for in pointing the telescope, and half the sky is invisible at any instant. Orbiting has full access to the whole sky, and no pesky stray forces on the mirror.

Re:Awesome

[SecurityTheatre]

All of these things are why the James Webb is going to go to the Lagrange point, rather than orbit.

Orbit is a dumb place to be for a telescope. :-)

Finally!

[GeekZilla]

We can finally quiet the "moon landing was a hoax" nutjobs. With the ability to make long-exposure images that resolve objects just 0.02 arcseconds across — the equivalent of a dime viewed from more than a hundred miles away", we can actually take pictures of all the junk we left behind as proof that we were actually there.