[ATM] Edge Support was PLOP Calculations

["James Lerch" <jlerch1@tampabay.rr.com>]

----- Original Message ----- 
From: "Nils Olof Carlin" <nilsolof.carlin@telia.com>

> I get the impression you plan to eliminate friction forces in the tangential
> direction - I'm not sure but I believe those forces are pretty innocuous.
> What I am sure isn't as innocuous by far is forces in the axial (parallel to
> the optical axis, pulling part of the edge forward-backward:
> http://w1.411.telia.com/~u41105032/sling/sling.htm
> So I believe the bearings at the edge should roll in the direction
> towards/away from the mirror front.

Nills,

Excellent description of the exact problem Ron and I have with his 22" thin
plate glass optic.  Your web page exactly describes what were seeing in the star
test.

I can't add much, other than to strongly agree with the statement on your
website that reads:

"However, even very small forces that are not in the plane of the mirror will
have disastrous consequences for the performance - a fact that I feel have not
been given the deserved consideration in amateur literature"

> Perhaps a (moderately but sufficiently heavy) sling of steel wire (easier
> than a chain), strung with small ball bearings at suitable distances (with
> spacers in between) would do the trick - suspended to touch the mirror at
> the level of its COG.

Interesting thought, something like a string of pearls.   My thoughts had been
focusing on the sling support post, and how to give it 4 or 5 degrees of
frictionless freedom.  Moving some of that freedom down to the sling itself sure
seems to be a more elegant solution!

Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)

"Anything that can happen, will happen" -Stephen Pollock from:
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