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The maximum resolving power of a satellite with a 2.4m (8 foot) lens, at 650 km (400 miles) orbit, is 10 cm (4 inches). The Hubble is in a circular orbit so I don't see how it can do better than that. http://everything2.com/title/Spy+satellites+can%2527t+read+y... Spy satellites often use highly-elliptical orbits to swoop closer, say 320 km (200 miles) for part of their orbit.

edit OK I might have found an answer actually. Using multiple exposures from different angles, you can resolve an object as if you had a lens that spans the entire angle. https://en.wikipedia.org/wiki/Aperture_synthesis I'm sure the movable secondary lens helps with this :) I'd heard of this technique used by ground-based radio telescopes before, and according to Wikipedia, the ability to do this within the visible spectrum has become possible only recently.




Every time I read about this, I instantly wonder whether this means that I can turn my crappy consumer camera into a spy device.

We have windows that span about fifty feet in the office, and a hotel across the street; if someone left the complimentary bible in the window open to a random page, could I combine multiple exposures into an image detailed enough to read the text?

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Not using that technique, since it requires that you measure the phase of the incoming light. But there are some super-resolution techniques that might double a noisy digital sensor's performance. https://en.wikipedia.org/wiki/Super-resolution Try the ClearCam iPhone app.

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Kind of a bummer that ClearCam is apparently abandon-ware now, yet still up in the store for $2.

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Oh, maybe HD Camera? http://itunes.apple.com/us/app/hd-camera-13mega/id455960193?... I don't have an iPhone so I can't try it :(

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