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Not sure if this is a Physics related or Engineering related question, but imagine that we would take 100's of small hobby telescopes and somehow managed to point them all at the same point in the sky at the same time. We would than digitally process this image.

Would we be able to combine these images and get image quality of a much larger telescope? We assume that all of them would point at a same part of sky at the very same time. Do you think we could get a significantly improved image compared to individual telescopes? And if so how much of a better image would we get?

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  • $\begingroup$ This question is better suited to Physics. Something similar to what you're asking about is already done for radio telescopes. I'm not aware of it being done for optical telescopes however. $\endgroup$ – Fred Apr 26 '18 at 3:59
  • $\begingroup$ @Fred there are a few places where a few large telescopes are paired to provide better results than any single one could provide. For example the VLT $\endgroup$ – ratchet freak Apr 26 '18 at 10:43
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There are two issues here, noise and resolution.

Combining the optical images from multiple telescopes would reduce the overall noise. This is because each image is independent of the others, so all the noise would be uncorrelated. Averaging multiple images attenuates uncorrelated noise.

You wouldn't really get any enhancement of resolution. There are techniques for combining the data from multiple telescopes to get higher resolution, but you need to capture phase information for that to work. This is essentially past our capability for separate optical telescopes. However, this is being done rather routinely at lower frequencies where capturing phase is possible. There are radio telescope arrays that were specifically built to act as one large-aperture receiver.

There have even been cases where multiple radio telescopes around the world have cooperated in imaging the same distance object. The data from each telescope is carefully recorded and time-stamped. The result requires lots of computing to decipher into a image. If done right, the effective aperture can be a good fraction of the diameter of the earth.

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coupling together a large number of small telescopes to emulate the behavior of a single very large telescope is an area of active research in the telescope field. to properly combine a large number of optical images into one requires phase-matching all of the separate signal sources, which is a difficult job when dealing with light. it is easier in radio astronomy because the wavelengths involved are much longer; for this reason, the combination trick you describe has been in use for many years in that arena, where it is capable of producing resolution equivalent to that of a radio telescope "aperture" many miles across.

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  • $\begingroup$ you can use movable mirrors to adjust the length of the path to do your phase matching. $\endgroup$ – ratchet freak Apr 26 '18 at 10:45
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    $\begingroup$ @rat: In theory, but there are severe engineering problems with this in practice. The mirrors would need to be controllable to around 10 nm resolution. Just getting a mirror flat to that level is not easy, let alone adjusting for path length changes due to temperature. Then correlating the phase between multiple independent telescopes at optical wavelength between telescopes dispersed around the world is beyond our current capability. Way beyond. $\endgroup$ – Olin Lathrop Apr 26 '18 at 14:44

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