ATM Secondary Fab/Bill's Compound Scope

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

Hi Folks:

When we ended last time, Primary has been laid to rest. Outside testing 
confirms (ronchi test, better than 1/8th wave according to Paul 
Zurakowski over at Chabot College) my multiple tests with TEX giving 
multiple results at Better than 1/10 wave. Rouge has given me a very 
smooth mirror, the very faint center zoning remaining from my local 
retouching experiment 8+) will be covered by secondary and baffeling, 
so ....

So, secondary is being rough ground, sag almost where it's supposed to 
be, so a couple of timely questions:

1)As I'm making the secondary oversize (2.5"), for ease in polishing 
and figuring, and plan to edge down on the diamond wheeled edger I have 
at work, to it's final 1.6" dia, I'm concerned about relieving stress 
as I do this, tweeking the final figure. 
I guess its not that big of a deal, I can always refigure it, and I may 
have to do more figuring on it anyway as I autocollimate the system,
so, ?? Comments?

Also, somewhere in my archives of S&T and TM I remember seeing an 
article on figuring a Cass. secondary, that concerned itself with 
the changing focal length as the mirror was figured to its 
hyperbolic shape from a sphere. However, tried to find it today and 
couldn't (I'm pretty sure it was in TM).

If any one knows the specific location of this article, or info on the 
calculations, or info on whether or not this is a real concern, the ROC 
of the secondary is supposed to be 19.412" when done, If I knew more 
about raytracing (I'm working on it!) I should be able to tell how much 
error is allowed, I assume, but I'm not at that point yet. I'd 
appreciate any comments relating to such. 

Thanks, as usuall....8+)

Bill Marriott
Forest Knolls, Ca. USA
btk@ix.netcom.com