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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.
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!
Add up 1000 of those frames, and you have a 50 second exposure.
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?
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.
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