Neptune images from VLT better than Hubble

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  • #2
berkeman
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Nice, thanks Tom.
Adaptive optics is a technique to compensate for the blurring effect of the Earth’s atmosphere, also known as astronomical seeing, which is a big problem faced by all ground-based telescopes. The same turbulence in the atmosphere that causes stars to twinkle to the naked eye results in blurred images of the Universe for large telescopes. Light from stars and galaxies becomes distorted as it passes through our atmosphere, and astronomers must use clever technology to improve image quality artificially.

To achieve this four brilliant lasers are fixed to UT4 that project columns of intense orange light 30 centimetres in diameter into the sky, stimulating sodium atoms high in the atmosphere and creating artificial Laser Guide Stars. Adaptive optics systems use the light from these “stars” to determine the turbulence in the atmosphere and calculate corrections one thousand times per second, commanding the thin, deformable secondary mirror of UT4 to constantly alter its shape, correcting for the distorted light.
 
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  • #4
sophiecentaur
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New adaptive optics does an amazing job.
I was at a presentation by E2V, the sensor designer and manufacturer where it was pointed out that the adaptive optic system uses an 'artificial star, which is projected by a Sodium Yellow laser on the upper atmosphere. The 'point source' that's produced up there is not distorted significantly as there is just one path from the laser through the atmosphere. The images from the various elements in the multiple reflector are registered together to reduce the effects of the different paths.

Actually, a single, smaller reflector can produce a better image than the uncorrected large reflector will produce so the 'before and after' images should be viewed with that in mind. I found it hard to find examples of images taken from Earth but there are a couple of images, taken by an amateur, near the bottom of this link. They are obtained with a 350mm scope.

The professionals seem not interested in images that. a few decades ago, would have been 'stunning'.
Perhaps someone else could supply better examples of good amateur images or early professional ones???
 

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