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BigPapaSmurf
SFN Die Hard
3192 Posts |
 Posted - 02/28/2006 : 11:01:54
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http://news.bbc.co.uk/1/hi/sci/tech/4756346.stm
Instead of using the background stars to correct the lens shape, this new system shines a laser into the atmoshpere creating a much more reliable 'artificial star' with which to correct atmospheric blurring. Who needs Hubble anyway.
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"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 02/28/2006 : 11:15:00 [Permalink]
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Thanks, BigPapa. Big WOW! It's hard to imagine being able to correct the image in real time by reshaping a mirror constantly, but there it is. And the future interferometry of the linked telescopes will be even a more remarkable accomplishment.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 02/28/2006 : 15:26:11 [Permalink]
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| I remeber reading about laser-controlled adaptive optics a few years ago! This can't be a new article. Or, if the article itself is fresh, the technology has been around for a while. |
Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
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"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
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Collateralmurder. |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 02/28/2006 : 15:42:03 [Permalink]
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Mab said: quote:
I remeber reading about laser-controlled adaptive optics a few years ago! This can't be a new article. Or, if the article itself is fresh, the technology has been around for a while.
I know the corrective technology has existed for a while, but it still amazes me. Its application to those particular telescopes, which are still being buiilt, is new and perhaps the most advanced example of this technology.
I'm impressed that the optics can be corrected so swiftly, literally in midst of the twinkle of a star.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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Dude
SFN Die Hard
USA
6891 Posts |
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Randy
SFN Regular
USA
1990 Posts |
Posted - 02/28/2006 : 15:57:32 [Permalink]
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Here in Austin, Tx, there's a group of backyard astronomers meeting on clear weekend out at the dam. A few of them use a scaled down version of it on their own scopes.
Must be a slow news day.
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"We are all connected; to each other biologically, to the earth chemically, to the rest of the universe atomically."
"So you're made of detritus [from exploded stars]. Get over it. Or better yet, celebrate it. After all, what nobler thought can one cherish than that the universe lives within us all?"
-Neil DeGrasse Tyson |
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JohnOAS
SFN Regular
Australia
800 Posts |
Posted - 02/28/2006 : 22:53:36 [Permalink]
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quote:
Originally posted by Dr. Mabuse
I remeber reading about laser-controlled adaptive optics a few years ago! This can't be a new article. Or, if the article itself is fresh, the technology has been around for a while.
That is has. I remember back when I was working at Macquarie University (I'd only recently graduated fro the same) back in the early/mid 90's, we worked on some copper vapour lasers with some of the people from a group at Oxford Lasers in the UK. One of the guys set up some mirrors from the lab, through the safety doors(!) down the corridor and out over the building balcony and up into the sky, just to impress a bunch of people at an open-to-the-public astronomy night. Our laser was only around 20 mm diameter, unlike the big ones Oxford built for the guide star project, which were around 1.5m diameter. Needless to say, OH&S was less popular back then. 
And an example of the corrected image.
In both cases you can click on the pic for a larger version.
I actually visited Oxford labs in the UK a few years ago for another project. I personally found the high speed imaging stuff more fascinating (it's a little more "hands on"). You can take some pretty neat pics when your camera flash pulse width is only nanoSeconds wide.
Both of these pics were lifted from a presentation by Colin Web, available here. |
John's just this guy, you know. |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 02/28/2006 : 23:16:35 [Permalink]
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John, should we be looking for "guide laser" pulses from ETs calibrating their optical telescopes?
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 03/01/2006 : 08:38:58 [Permalink]
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quote:
Originally posted by HalfMooner
John, should we be looking for "guide laser" pulses from ETs calibrating their optical telescopes?
Doubtful that it will do any good. Though the light in itself have a very unique signature, the radiation energy is extremely low compared to thermal radiation as well as reflected light from the atmosphere. The albedo of Moon is 7%. The radiation energy hitting it is ~1,5kW/m2 perpendicular to the sun. 105W radiation is reflected from each square meter. This reflected radiation is spread 180° from that surface, with a maximum depending on the surface angle. But there are many square meters of reflecting surface. The Moon is said to have roughly the same "size" as Australia which would mean 7,686,850,000,000 mē (Wikipedia). Full moon would equate to 7700 billion 100W lightbulbs (one per square meter).
Earth's albedo is ~30% (four times as high as the moon) and many times the size.
How coherent is the beam of the laser?
Edit: Not coherence, I meant to say "What Beam Divergence does the laser have?" |
Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3
"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
Support American Troops in Iraq:
Send them unarmed civilians for target practice..
Collateralmurder. |
| Edited by - Dr. Mabuse on 03/01/2006 08:44:33 |
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JohnOAS
SFN Regular
Australia
800 Posts |
Posted - 03/07/2006 : 04:27:36 [Permalink]
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quote:
Originally posted by Halfmooner
John, should we be looking for "guide laser" pulses from ETs calibrating their optical telescopes?
It's an interesting idea, but detecting good old fashioned "radio waves" (what we happen to call some of the wavelengths significantly longer than "visible" light) is much easier for us, and more likely to prove successful. It's still a lot easier to build a big radio telescope than an optical telescope.
If you look at human history, by the time we evolve enough to think about what sort of message we ought to be sending out to let others know about us, it's too late. They've already received our earliest attempts at communication. If they happen to decode some bad sitcoms before anything else, they probably already have us targeted for extermination. 
quote:
Originally posted by Dr. Mabuse
How coherent is the beam of the laser?
Edit: Not coherence, I meant to say "What Beam Divergence does the laser have?"
Copper lasers can be pretty good, they have a relatively big beam width (compared to most solid state lasers) of several mm to several tens of mm. They can be pretty close to(a couple of times or thereabouts) the diffraction limit, which, for a beam diameter of 20 mm is 6.5 x 10-7 radians. This is still a spot size of around 250 metres on the moon, so it's going to be a lot bigger (and proportionally less intense) by the time ET gets it.
The ones for the guide stars are beam expanded up to around 1.5m diameter at the earth end, but convergent in order to result in a focal point at the target location in/above the atmosphere.
Disclaimer: These calcs were done pretty roughly, and late in the evening, so feel free to second guess me. |
John's just this guy, you know. |
| Edited by - JohnOAS on 03/07/2006 04:28:33 |
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ktesibios
SFN Regular
USA
505 Posts |
Posted - 03/09/2006 : 14:54:35 [Permalink]
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quote:
Originally posted by JohnOAS
If you look at human history, by the time we evolve enough to think about what sort of message we ought to be sending out to let others know about us, it's too late. They've already received our earliest attempts at communication. If they happen to decode some bad sitcoms before anything else, they probably already have us targeted for extermination.
Or the first extraterrestrial message that SETI@Home detects and decodes will read something like "Either we see some new episodes of I Love Lucy or your planet is toast" |
"The Republican agenda is to turn the United States into a third-world shithole." -P.Z.Myers |
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JohnOAS
SFN Regular
Australia
800 Posts |
Posted - 04/27/2006 : 22:28:27 [Permalink]
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quote:
Originally posted by HalfMooner
John, should we be looking for "guide laser" pulses from ETs calibrating their optical telescopes?
Someone obviously thinks the little green men will be signalling us with their laser pointers. Nice idea, but I still stand by my earlier arguments.
Check out this this article from New Scientist titled "Looking for alien lasers, not radios" |
John's just this guy, you know. |
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