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Sharpest Images With "Lucky" Telescope
igny writes "Astronomers from the University of Cambridge and Caltech have developed a new camera that gives much more detailed pictures of stars and nebulae than even the Hubble Space Telescope, and does it from the ground. A new technique called 'Lucky imaging' has been used to diminish atmospheric noise in the visible range, creating the most detailed pictures of the sky in history."
First post, huh.
This technique is often used by amateur astrophotographers using newer CCD cameras and even webcams. Astronomy Picture Of the Day http://antwrp.gsfc.nasa.gov/apod/astropix.html is a great site to see this stuff. I haven't checked Googles pictures, but I am sure that there would be a number of them there, too.
The quality of some of these photos is amazing.
davel
dot-sig.
...can the same be applied in space telescopes to get rid of the interference of the gas clouds they're looking at?
I'm just blowing smoke here, but it seems to me that a technique designed to compensate for atmospheric distortion might not be all that useful when there's no atmospheric.
The higher the technology, the sharper that two-edged sword.
TFA states that the camera takes 20 frames per second. Aren't most exposures of deep space objects on the order of seconds or minutes (or longer). Seems like 1/20th of a sec wouldn't cut it for all but the brightest objects.
One of the main limitations to ground-based optical telescopes (and one of the reasons that Hubble gets such amazing images) is that the atmosphere generates considerable distortion. Random fluctuations in the atmosphere cause images to be blurry (and cause stars to twinkle, of course). The technique they present appears to be taking images at very high-speed. They developed an algorithm that looks through the images, and identifies the ones that happen to not-blurry (hence "lucky"). By combining all the least blurry images (taken when the atmosphere just happened to be not introducing distortion), they can obtain clear images using ground-based telescopes (which are bigger than Hubble, obviously). I imagine the algorithm they've implemented tries to use sub-sections of images that are clear, to get as much data as possible.
Overall, a fairly clever technique. I wonder how this compares to adaptive optics, which is another solution to this problem. In adaptive optics, a guide laser beam is used to illuminate the atmosphere above the telescope. The measured distortion of the laser beam is used to distort the imaging mirror in the telescope (usually the mirror is segmented into a bunch of small independent sub-mirrors). The end result is that adaptive optics can essentially counter-act the atmospheric distortion, delivering crisp images from ground telescopes.
I would guess that adaptive optics produces better images (partly because it "keeps" all incident light, by refocusing it properly, rather than letting a large percentage of image acquisitions be "blurry" and eventually thrown away), but adaptive optics are no doubt expensive. The technique presented in TFA seems simple enough that it would be added to just about any telescope, increasing image quality at a sacrifice in acquisition time.
DIY.
DMCA, Hollings, Palladium. What might have sounded like paranoia is now common sense.
That is really quite amazing, and reminds me a bit of the jumping spiders whose retinas vibrate to increase their optic resolution.
N4st0r, trixx0r h0bb1tz0rz! Th3y st0l3 0ur pr3c10uzz!
Terrorists can't threaten a country's freedom and democracy. Only lawmakers and voters can do that.
"Every vision is a joke until the first man accomplishes it; once realized, it becomes commonplace." -Robert H. Goddard
As the previous poster noted, there isn't any atmosphere and thus the technique isn't useful for HST.
Additionally, while they don't mention details in the article, I presume they have a specially designed camera. This is an old technique, but it's generally limited to very bright objects due to something called readout noise. Basically all CCD's produce an additional signal due to the process of reading out the data. This limits the effectiveness of repeated short observations to sources which are much brigher than this noise, since the noise also grows linearly with the number of images taken.
To image distant galaxies you typically have to take exposures of one to several hours, and thus this technique isn't useful.
Doug
Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
THere's several pieces of software which do som parts of this - Registax is what I use, but amateurs usually only have enough aperture to make this work for bright objects like planets. You can take a good quality webcam (the top of the line Phillips webcams are the best bang for yout buck), record some video of a planet through a telescope and then pick out the least distorted images before adding them together to create the final image. Now, the trick is getting the best measurement of which images are undistorted, and getting enough light in each frame while keeping the esposure time short enough to beat the atmosphere.
Look at the planetary images here for my attempts at this technique.
TFA mentions that they can achieve images better than Hubble. The sample image they show, of the Cat's Eye Nebula, isn't as sharp as the Hubble image of the same object.
Probably they can push their technique harder than this initial image suggests (it was mainly comparing the "lucky" image with a conventional, blurry, ground-based image)... But I just thought it would be good to show Hubble's pictures alongside.
Additionally, while they don't mention details in the article, I presume they have a specially designed camera.
I _Why%20Now.htm
n dex.htm
They are using a new kind of CCD that somehow lowers the noise floor. Details are at:
http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/L
In fact this site (same basic place) is much more informative than the press release and answers a lot of questions:
http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/i
Just went and looked up the Cat's Eye Nebula as taken by the Hubble. Lot more detail. What gives? Someone able to explain that, please?
I would think that before the scientists claim victory over Hubble, let's see their camera best some of Hubble's best work:
http://hubblesite.org/
There's a number of excellent Hubble images of just about everything in our solar system to the most distant galaxies.
I would put my money on Hubble, for two reasons.
First, the averaging algorithm is not without its flaws. They make the assumption that by averaging out a bunch of images, you eliminate distortion. For this to work, you have to assume that the probability of a particular pixel being in the right spot is higher as the distortion would essentially be random, and that could theoretically not be the case. If the distortion is completely random, then, averaging a set of images would essentially lose the pixel that is being pushed around its "real" spot by the atmosphere, and you can actually see that, as the corrected images still look muddy compared to their HST or even adaptive optic counterparts.
Secondly, the atmosphere doesn't just distort light, it also filters it. You can use averaging to remove distortion "noise", but, there's really no way to ascertain what information was removed by the atmosphere.
The bottom line is, yes, you can get some pretty good results with averaging software, but, if you have money to spend, the best images are going to be space based, and its still going to cost a billion dollars. Given the promise the heavens hold for the advance of human understanding, let alone essentially infinite resources, one only hopes that policy makers will not be mislead by the outrageous claim that one can get the best images from the ground. You can't. HST should not be thought of as an aberration made obsolete by adaptative optics or the low budget averaging. Low budget averaging and adaptive optics really need to be thought of as getting by until we can put larger, and better visible wavelength telescopes into space.
Imagine what a space based Mt. Palomar sized mirror could do, if in space!
This is my sig.
using 'Blue Peter' technology
Blue Peter is a BBC childrens show. Blue Peter Technology is effectively something so simple a child could do it.
A feeling of having made the same mistake before: Deja Foobar
The technique they're using, while interesting, needs more justification.
I'm wary when I see people doing any selection on random data because there's the problem of selection bias; throwing away the hundred results that don't match what they want and keeping the one that does. Just getting an image that seems plausible is not good enough.
Their quality measure isn't one I'd use. They should be comparing the technique-plus-low-resolution-optics against high-resolution-optics directly. That is, doing image differencing of images taken at the same time and seeing what differences there are. They may well have good reason for assuming it's all okay but until somebody does that test they cannot assume they've removed all the variability that the atmosphere provides; there could be all sorts of hidden biases due to various atmospheric, molecular and statistical effects.
---
"Intellectual Property" is unspeak. All inventions are the result of intellect. A better name is ECI - easy copy items.
Actually, near infrared is not blocked by water vapor, in fact water vapor is extremely transparent to near infrared light even moreso than visible light. That's why satellites can use infrared to see through clouds, and also why adaptive optics work so well in the near infrared range.
Far infrared is a different story, and you're absolutely correct there.
Random and weird software I've written.
I'm curious though about how they deal with some of the "features" you get to see with this technique. It's *very* easy to stack a few hundred images, run Registax's sharpening filter and get some interesting pictures of stuff that doesn't really exist. I'm not sure I really trust the fine detail in my photos- unless I see it in another taken a few hours later it may well not be real.
"Seven Deadly Sins? I thought it was a to-do list!"
See here, for example, for more information.
There are wavelength ranges in the NIR where the atmosphere is indeed transparent (J,H and K bands, for example); but the atmosphere is opaque at most NIR wavelengths (and, even at those IR wavelengths where the atmosphere is transparent, the transmittance is lower than at visible or radio wavelengths). See here for more info.
Even if this technique can eventually produce better pictures at lower cost it is still limited to wavelengths that can penetrate the atmosphere. Some of the most exciting recent discoveries are in infrared (Spitzer) and X-ray (Chandra). The next big telescipe (James Webb Space Telescope) is also for infrared.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
Interstellar gas clouds are pretty static. You would have to take one image every, say, year or maybe 100 years to really get any difference in the image quality. Whereas the earth's atmosphere produces an effect almost exactly the same as if you were to look at the bottom of a swimming pool, and in about the same timeframe.
No, the images we get right now from space telescopes are the best we can get at any given epoch, and that's just the way it is.
"No problem. I have the capacity to do infinite work so long as you don't mind that my quality approaches zero."-Dilbert
I invented this process in 1995.
here is my original post on
the sci.image.processing newsgroup
my old email address is no longer active.
new one is geopiloot at mindspring.com 9 reduce the numbers of ooo's in pilot to one
it was ironic that many people jumped out to say it wouldn't work at the time.
it does work and it works well. In fact most of the additive image processing now done by amateur astronomers everywhere using pc's software is based on my invention which I did not patent.
George Watson
From: George Watson (71360.2455@CompuServe.com)
Subject: virtual variable geometry telescope
This is the only article in this thread
View: Original Format
Newsgroups: sci.image.processing
Date: 1995/12/11
Has anyone implemented a virtual variable geometry telescope using
only a CCD attached to a normal non variable telescope?
It would work like this:
Take extremely short duration images from the CCD at a frequency
faster than the frequency of atmospheric distortion (1/60 sec I have
read is the minimal needed timeslice for physically corecting
atmospheric distortion in real time so maybe an exposure of 1/120 sec
would be short enough).
Choose via computer a high contrast image as a reference image.
Continue to take rapid short duration images and keep only the high
contrast ones with that have minimal displacement/offset from the
reference image.
Sum each of those acceptable images to a storage that will become the
final image.
What you should end up with is a final image that has minimal
atmosperic based distortion because all the low contrast and non
matching images will have been discarded.
Obviously you build an image over a longer period of time than with
real time optical correction but at perhaps lower cost.
Anyone know whether this has been proposed/done or researched?
--
George Watson
The opinions expressed here are those of the fingers
of George Watson only; not those of George Watson himself.
Please reply via this newsgroup. No Email unless requested,
Thanks.
View this article only
Newsgroups: sci.space.policy
Date: 1995/12/30
To sum up, the problem is readout noise. The faster you read out the CCD, the more noise you get. When you image a faint object the readout noise exceeds the signal level. The reason amature astronomers can use this technique anyway is because they are imaging bright objects (like planets), so the signal is easily discernable from the readout noise.
Now there is a new type of CCD with a built in digital signal multiplier that precedes the readout step in each individual pixel. You can simply select an appropriate multiplier that gives pixel values that fall nicely in the middle of the register width and when you read out the value, any noise can simply be subtracted away because you know that it will be much less than the signal value you are looking at.
I emailed the principle researcher on this project, asking him what was novel about his approach, since amateurs have been "stacking" images for years. Below is his response: From: Craig Mackay [mailto:cdm@ast.cam.ac.uk] Sent: Tuesday, September 04, 2007 5:20 AM Subject: Re: What's new with Lucky? Dear Tom Thank you for your message. What is new about this (and gets rather lost with the media coverage) is being able to use lucky imaging on a much larger telescope. With a 2.5 meter telescope we are able to use typically 10% of the images. With a five meter telescope and four times the area we would be able to use only 0.01% of the images, a completely useless fraction! For the first time however we have managed to do it by using an adaptive optic system in front of our lucky imaging camera. That is what is new and that is what has made all the difference. The AO system gets rid of the larger scale low order turbulent distortions leaving lucky imaging to work on the higher frequency ones which it does rather well. Hence the new image quality which is twice as good in terms of resolution as Hubble, something that has never been achieved before either from space or from ground. If you look on the lucky website you will find a lot of information about amateur lucky imaging for which I have a very high regard. Best wishes Craig Mackay.
http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/in dex.htm/ refers to a 1978 reference (Freid). It seems that some ideas keep popping up, only the technology actually available to do it has progressed from imaginary to real.
Donte Alistair Anderson Roberts - hi son!
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