Re: ATM Be very careful

["Vladimir Galogaza" <vladimir.galogaza@zg.tel.hr>]

Re Frank's experience,

Some facts should be mentioned repeatedly from time to time. One of those
facts
is that we should treat the mirror as it is made of rubber. At orders of
magnitude we are working ( parts of wavelengths)
and at forces applied, flexures are inevitable and considerable.
There was very instructive mail from our friend Ulhas ( I think, or was it
Stathis?),
with central hill on his mirror, and rather stubborn one. He put a circular
 thin sheet of paper underneath the center  and soon hill disappeared.
This "Princess on pea" effect is basically the same as one Frank  described
as  consequence of the unsupported edge. Ulhas cleverly took advantage
of it. and Frank found out it soon enough to avoid  trouble.

Frank's well described experience will certainly have positive impact in
stressing importance of proper mirror support.

One remark in addition.
It will be helpful for archives search if subject title will reflect the
contents as
descriptive as possible. In this case "unsupported edge effect on polishing"
 will perhaps be more appropriate ( in the long run)  than " Be very
careful".

Vladimir.