From: kragen@pobox.com
Date: Fri May 11 2001 - 23:48:55 PDT
Eirikur Hallgrimsson <eh@mad.scientist.com> writes:
> I think a space telescope could be seriously cost-reduced. The mirror, after
> all, could be a foil or membrane of some kind, probably in an array rather
> than as single big piece. This lends itself to focusing at different
> frequencies, which I've not heard about anyone doing except by playing with
> where the focus falls.
I don't think mirrors focus different wavelengths of light in different places.
It's probably possible to build a mirror the way you're describing,
but it isn't easy. The surface of the mirror needs to approximate a
parabola to within a fraction of a wavelength of the light you're
interested in focusing. (Shorter wavelengths can be focused into
sharper images, given the same mirror.) Positioning all the elements
of an array of large mirrors relative to one another to a precision of
50-100nm will not be easy.
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