ATM Re: PUSHING instead of pulling?

["Bill Kelley" <flex@commspeed.net>]

Dear list,
Thomas Simmons wants to flex a slightly(?) hyperbolic mirror by reverse
flexing it. He has been e-mailing me off list. The problem and subject may
be of interest to list members and I am posting this reply to the list. FWIW
if a mirror is a bit undercorrected or overcorrected a simple flex cell with
only a center bolt for push or pull may be an easier fix than re-figuring
the mirror.
Regards to all,
Bill Kelley

Thomas,
Quite so, it won't hurt to experiment. Some notes:
1. Plywood is not a good choice to make a flex cell, it bends along the
grain.
2. I don't believe you intend to use a 3-blob support in your flex cell.
3. The edge of the mirror will have to be glued to the pusher ring since you
are not pulling down on the mirror.
4. You need not bother making a pusher plate. A bolt head attached to the
center of the mirror and pushed will give you good correction if the mirror
is only slightly parabolic. Adjust the push while star testing.

Regards- Bill Kelley


Subject: Re: PUSHING instead of pulling?


>
> Thanks, Bill, and Roger on the crux of the issue "is it TRULY hyperbolic
> or just a turned up edge". BTW, it's an F10, and just breathing on this
> mirror...
> Currently on a "trendy" plywood disk with 3 silicone globs.
>
> Hmmmm, never hurts to experiment, as long as I don't drop the mirror, eh?