Re: ATM Turned edge on Diagonals?

[Bill Marriott <btk@pacbell.net>]

Jim Miller wrote:
> 
> I've seen several statements that something like 1/4 in > on a diagonal mirror is lost to edge issues.  Is this > always the case? 

Jim:
 
No, if properly made, they should be smooth to the edge. Like with a
turned edge, you can always blacken it out, but one shouldn't have to. 

> Can a blank be generated  oversize, made flat then the > offending edge be ground away?  I assume this costs >money but is it done?
> 

Yes, we do that on occasion, and while it is not recommended to grind
the back of a flat optic, due to stress relief and the accompanying
change in figure, it  is possible to change the OD, without a change in
figure.

Go figure 8+)

Bill
--
Bill Marriott
http://www.starlightoptical.com
telescope/optical stuff