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Posted by Henry Spencer on June 2, 2007, 5:39 pm
Please log in for more thread options > Then could this mean that rather than needing a single large mirror
>you could combine the light from small, widely separated mirrors to
>create a single high resolution image, as has been done for radio
>astronomy for several years?
Yes. Various groups have been working on this for the last 10-20 years;
the idea is not new, although it's difficult and practical use of it is
still quite experimental. Interferometry is why the European Southern
Observatory, for example, was built with four huge telescopes rather than
just one.
Huge telescopes? Yes, even with interferometry! It tends to require a
fair amount of light -- you need a substantial number of photons per
second to form detectable interference fringes -- so it does work better
with lots of mirror area.
> This would be especially useful for space telescopes where you don't
>have to worry about using adaptive optics (which works better in the
>infrared rather than the optical.)
Yes and no. The problem in doing it with space telescopes is that the
spacing between the mirrors has to be controlled very tightly indeed, to
a fraction of the wavelength of light, so there are real advantages to
having them firmly anchored to something heavy and solid. People are
working on doing it in space, but the challenges are even greater.
Most "optical" interferometry is likewise done in the near infrared rather
than the visible, for the same reason as for adaptive optics: the longer
wavelength makes all sorts of optical things easier.
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