wrote:

Just seen some pictures of Hubble, and The "Very Large Telescope"
(original name) in Chile. It made me think.

With a reasonable space based industry, moon mining, metal working,
aluminium and glass production, precision engineering, how big an
optical telescope could be built in zero-g?

What are the limits? Could a 100m diameter optical telescope be built?
what would it see?

I don't see any reason in principle (as opposed to the actual
engineering) why you couldn't make a parabolic mirror of almost any
size.

Of course, where any planetary surface is involved, sooner or later
there will be deformity and sag issues. And a sufficently massive mirror
(with associated framework and/or tube up to the focal point) in free
fall would be difficult to steer and track. Espically if orbiting deep
in some gravity well, where there would be a tendency to line itself up
with the planet's center of mass.

But you'll likely have observed plenty of neat new stuff (including,
I would think, direct imaging of extrasolar planets) well before
reaching those limits...


As for radio telescopes, what are the limits are baseline inferometry?
what would a few telescopes, each say 3km across, in solar orbit, say 1
billion km apart be able to achieve?

Problems here are somewhat similar to those in optical, except that
minute deformations of the parabolic surface are less critical at these
wavelengths.

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