Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Sundowner on September 04, 2007, 05:10:01 AM
-
What a neat innovation in Astronomical Optics!
Regards,
Sun
http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/LI_Press_Releases_0807.htm
A team of astronomers have taken pictures of the stars that are sharper than anything produced by the Hubble telescope, at 50 thousandths of the cost.
The researchers, from the University of Cambridge and the California Institute of Technology (Caltech), used a technique called “Lucky Imaging” to take the most detailed pictures of stars and nebulae ever produced – using a camera based on the ground.
Images from ground-based telescopes are usually blurred by the Earth’s atmosphere - the same effect that makes the stars appear to twinkle when we look at them with the naked eye.
The Cambridge/Caltech team, however, surpassed the quality of images taken from space by using a high-speed camera to take numerous images of the same stars at a rate of 20 frames per second. Because of fluctuations in the atmosphere, some of these were less smeared than others. The team then used computer software to choose the best images, and these were combined to create pictures far sharper than anything that has been taken from space.
Dr Craig Mackay, from the Institute of Astronomy at the University of Cambridge, who led the research, said: “To produce images sharper than Hubble from the ground is a remarkable achievement by anyone’s standards.
“These are the sharpest images ever taken either from the ground or from space and yet we are essentially using ‘Blue Peter’ technology. Amateur Lucky Imaging is popular because the technique is so cheap and effective. The low cost means that we could apply the process to telescopes all over the world........”
-
sundowner.. what is that icon you use a picture of?
lazs
-
i was reading about this last night. terrific advance.
the article that i had read made no mention of the images being clearer than hubble though, just that they had some that came out on par...
they described the technique as being something like looking at an object through a rising heat column...that the air bends and distorts but sometimes the object is unobsructed and clear in pockets.
-
Laz its the Dark Tower.
-
What if they'd do the same with Hubble, would it create even sharper images?
-
It sounds like the software is responsible for the sharp images, not the camera itself. I wonder whether the author is referring to the software or the camera when he says "50 thousandths of the cost".
Fantastic achievement. I'd always thought the effects of the atmosphere on picture quality were immutable, so we HAD to build the Hubble to get quality shots.
-
i remember talking with a guy who used to do satellite tracking for norad.
he hinted that there were two mirrors made for the hubble.
in a later conversation he suggested that a big satellite like that would be great for analysis of the earths surface at very high resolution.
i was like. oh. ya. ...i guess it could be.
anywho...
-
Originally posted by Fishu
What if they'd do the same with Hubble, would it create even sharper images?
Space based telescopes don't have to compensate for atmospheric twitching, so this technique would be wasted on it. If the images are better after all the processing, it's probably because the imaging array/ccd is of newer technology than the one in the Hubble. Put a modern imager in it, and it'd probably do pretty good.
-
All that selection and computer finagling ... are we sure the resulting doctored images are absolutely accurate or are they merely possible approximations?
For example, I can take 20 pictures of someone and select several and construct one photo from them. But would that be a totally accurate photo of the subject? I don't think so. It would be something maybe a little more accurate than a painting is to an unretouched photograph.
On a related topic, saw an expensive book of satellite photos of various Earth scenes. None were natural color. All were filtered by this and that. Interesting, but first I'd like to see each picture as natural as possible, then any filtered effects.
-
Originally posted by JB88
i remember talking with a guy who used to do satellite tracking for norad.
he hinted that there were two mirrors made for the hubble.
in a later conversation he suggested that a big satellite like that would be great for analysis of the earths surface at very high resolution.
i was like. oh. ya. ...i guess it could be.
anywho...
i missed that question on the philosophy test.
:(
the hubble telescope is real?
-
Originally posted by lazs2
sundowner.. what is that icon you use a picture of?
lazs
It's the dark tower, a series called The Gunslinger series by Stephen King. The first four books were phenomenal. Downright amazing. The fifth book got a little weird, and not in a Stephen King sort of way. I mean you'd be sitting there thinking to yourself, "That's lame." The sixth did also even more so. The seventh book was so strange that I didn't get more then a chapter or two in before I refused to read anymore.
I'm split as to whether or not I'd recommend it to anyone. I can't tell if the first 4 books makes up for the last two's awfulness.
-
Originally posted by JB88
i remember talking with a guy who used to do satellite tracking for norad.
he hinted that there were two mirrors made for the hubble.
in a later conversation he suggested that a big satellite like that would be great for analysis of the earths surface at very high resolution.
i was like. oh. ya. ...i guess it could be.
anywho...
Since Hubble is quite probably based on technology developed for KH-11 spy satelittes, I would say your NORAD buddy is correct.
-
Originally posted by lazs2
sundowner.. what is that icon you use a picture of?
lazs
Yep, Lazs..like the other guys said, it's SK's Dark Tower series.
It's book art from the seventh in the series in which Roland, the main character, finally reaches his goal. (The Dark Tower)
Regards,
Sun
-
Neat. a super CCD camera.
Hubble's pics are super good because of the exposure time. That thing stared into a spot in space for like 3 days straight. No earth based scope can do that.
OTH, the CCD camera taking an ungodly amount of pictures per second in a decent time frame (4 hours?) should achieve similar results but as the name has it, its 'luck based'.
The CCD images would not be a like a photoshopped picture because they are all images of the same spot in the sky. The only difference is that the software in the CCD imager 'pieces' together the image, pixel by pixel, after sorting out each pixel from the 100+ pictures taken of the same spot.
Kinda like an amateur photographer and a proffessional photographer both taking pictures of an object using the same camera (set fixed on a tripod). The camera's settings and focus are reset before each person takes the picture. You process the pictures in the CCD software and the image will come out even better than the proffessional photographer's version.. because the amateur may have focused on something the pro did not and the software replaced the out-of-focus pixels from the pro's pix with the amateur's pixels.
-
Originally posted by Engine
It sounds like the software is responsible for the sharp images, not the camera itself. I wonder whether the author is referring to the software or the camera when he says "50 thousandths of the cost".
Fantastic achievement. I'd always thought the effects of the atmosphere on picture quality were immutable, so we HAD to build the Hubble to get quality shots.
Engine, I kicked around a bit at the "Lucky Imaging" website and found this explanation:
Why Has Lucky Imaging Not Been Possible before?
The principal difficulty with this method is the performance of the CCD cameras that are used at telescopes. CCD detectors are now very close to being theoretically perfect. They have nearly 100% quantum efficiency, superb imaging and cosmetic quality, are available in large areas (the biggest manufactured and sold commercially so far has 110 million pixels) and a very robust electrically and mechanically. Astronomers generally read out their cameras slowly (typically 30-500 kilohertz pixel rate) in order to minimise the readout noise, the noise that is added to every pixel, irrespective of the light level within it, because of the amplifier on the CCD output. If the CCD is read out quickly enough to be useful for Lucky Imaging (5-35MHz pixel rate) the readout noise is very much higher, typically 100 electrons per pixel per frame read. As an example, with Lucky Imaging we may select 4,000 images out of a total run of 40,000. If the readout noise was as high as 100 electrons per pixel per frame we would find that our summed image has a noise floor that is 64 times higher (square root of 4,000) than the single frame read noise. This would be 6400 electrons per pixel in background noise alone. This will have a dramatic effect on our overall sensitivity. A star image is detected over perhaps 10 pixels and therefore it would need to have something of the order of 300,000 electrons (detected photons) to get significantly above this background noise level.
What has happened recently is that an entirely new output structure (known as low light level CCDs or L3CCDs) has been developed for CCDs by E2V Technologies (Chelmsford, UK). Similar technology electron-multiplying CCDs (EMCCDs) have been developed by Texas Instruments (Japan). Both work by extending the output register with an additional section that is clocked with much higher voltages than usual so as to give a noiseless electron multiplication stage before the output amplifier. This signal amplification stage effectively reduces the readout noise of the on-chip amplifier by the gain factor of this multiplication register which may be set as high as many thousands. A single frame read out at high speed has essentially no readout noise with this technology. It is possible to build cameras that can see each and every individual photon detected by the CCD chip. The effect of this is that our limiting sensitivity is dramatically increased to perhaps only 30-100 detected photons from the reference star per frame, a factor of over 3000 on the above example. Lucky Imaging is therefore only possible because of this new technology which we have used in our experiments and observations. For more details of how EMCCDs work in click here.
Some of the photos at the site showing before and after comparisons are quite impressive.
http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/index.htm
Regards,
Sun
-
Originally posted by lasersailor184
It's the dark tower, a series called The Gunslinger series by Stephen King. The first four books were phenomenal. Downright amazing. The fifth book got a little weird, and not in a Stephen King sort of way. I mean you'd be sitting there thinking to yourself, "That's lame." The sixth did also even more so. The seventh book was so strange that I didn't get more then a chapter or two in before I refused to read anymore.
I'm split as to whether or not I'd recommend it to anyone. I can't tell if the first 4 books makes up for the last two's awfulness.
I made it almost all the way through the last book but just couldn't finish it. What a disappointment it was.
-
I don't understand a word about Lucky Imaging, but I've never heard it said better. :huh