Re: Question about telescope design.

On 26 Jan, 21:11, "Greg Neill" <gneill...@xxxxxxxxxxxxxxx> wrote:
<markz...@xxxxxxxxxxxxx> wrote in message

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On 26 Jan, 17:57, Chris L Peterson <c...@xxxxxxxxxxxxxxxxxx> wrote:

However, I've never seen it done with a strip mirror like you describe.
That's probably because making such a mirror (at least in the optical
wavelengths) would be very difficult. Grinding a large circular blank
into a spherical shape, which is then tuned to a paraboloid, is actually
easier than trying to make an accurate parabolic strip.

I don't think it would be, since it's only a 2D item, no compound
curves involved. It's just a matter of bending a nice reflective strip
into shape. It would be relatively easy to do on a frame, and to tune
with evenly spaced adjustment bolts. In fact the parabola could be
adjusted to focus onto a straight sensor like from a scanner.
It would actually be easier to adjust if it were quite big, say 2-3
metres.
If it's really big, a flat strip of thin glass could be bent to such a
parabola.

The 2D actually makes it more difficult. A 3D lens or mirror is
a shape that is self supporting and rigid for grinding and polishing.
A 2D strip would flex.

Obviously it's on a rigid frame.


How do you bend a strip to a parabolic curve that's uniformly
within 1/4 wave or less of the perfect shape?

By having regular spaced adjustments on the frame. (How big is a 1/4
wave?)
.

Relevant Pages

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