Re: [ATM] Flexed mirrors

["Mitchell R" <funnybone101@embarqmail.com>]

But don't most flexed mirror designs place a firm base at the back edges of
the mirror (e.g., a truck tire rim, as described in Guy's message), and then
pull back on the center of the mirror?  Wouldn't that give you an oblate
ellipsoid?  (I am now geometry expert, but I am looking at figure 20.1 Conic
sections from Rutten and van Venrooij as I write this)  In order to get a
paraboloid, wouldn't you need to do the opposite - pull back at the edges
(or push up in the center)?

Confused,
Chris Todd

	You say you haven't pushed glass. I don't know if you have read any
ATM books. Some have pictures of different ways a parabola can be made. The
"standard" method of deepening the center and edge leave the ROC relatively
the same. You could also dig out the center feathering to nothing at the
edge, or reverse; flatten the edge feathering down to no change in the
center. The last two will, in theory, produce parabolas with different focal
lengths then the spheres they were made from.
	Let me also note I don't really know how you would figure a mirror
in the second two ways. Only done the "regular" method of parbolizing on my
2 mirrors.

Mitchell  



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