(ATM) Secondary Fab/Conic Sections/Bill's Compound Scope

[btk@ix.netcom.com (Bill Marriott )]

As I start work on my secondary mirror (hyperbolic),  my original plan 
to make it oversize for convenience, and then edge it down to it's 
final 1.6" dia., getting rid of bad edge if necessary, I think will not 
work, and I thought I'd bounce this off, to see if my reasoning is 
sound. 

In a sphere, all sections of the sphere have the same shape, so that 
say a 2" dia of a given radius has the same figure as a 1" section out 
of the middle of that 2" dia piece.

In a parabola, and a hyperbola, the radius changes as you move out from 
the optic axis. 

My optic books are at work, so I'll hopefully have a chance to bang my 
head some more tomorrow, but the question is, 

 Is there a  difference in figure between a 1" f10 and the center 1" of 
 a 2" f5 for a hyperbola?

If I can figure this out mathametically, I'll let you know, 
Comments by others welcome.

Bill Marriott
btk@ix.netcom.com