many mirrors one focal point

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many mirrors one focal point

Postby lachlan » Fri Jun 13, 2008 12:00 pm

My question, since im planning on making my own telescope but don’t want to buy and expensive large mirror, or spend ages grinding my own and sending it away to get silvered is...
Can I use many small mirrors all with the same focal length to focus incoming light to one focal point? Will this be as effective (or close to) the light gathering capability’s of a single mirror with the same surface area?
lachlan
 
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RE: many mirrors one focal point

Postby brianb » Fri Jun 13, 2008 12:33 pm

[quote]Can I use many small mirrors all with the same focal length to focus incoming light to one focal point?[/quote]
Sort of, but the figure of the mirrors will all have to be different as the surface has to fit a paraboloid. I think it would be very difficult to make and mount such a mirror.

Of course, if you have plans to make a large aperture adaptive optics scope and have large amounts of computing and servo power available, such a design may be the only one which works effectively.

[quote]Will this be as effective (or close to) the light gathering capability’s of a single mirror with the same surface area? [/quote]
Yes, but there will be diffraction effects from the gaps between the mirror segments. This may not matter if your interest is DSOs.

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RE: many mirrors one focal point

Postby sftonkin » Fri Jun 13, 2008 3:03 pm

It's technologically feasible (it's done for big professional scopes) but, for anything under several metres in aperture (i.e. amateur scopes), the cost of preparing the smaller mirrors and their mountings will far outweigh the cost of a single large mirror and its mountings.
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RE: many mirrors one focal point

Postby lachlan » Mon Jun 16, 2008 1:20 pm

ok, thanks guys that helps me make a desision.
lachlan
 
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