Re: [ATM] 6-point cell?

[Mike Lockwood <melockwo@uiuc.edu>]

Hi,

me wrote:
> I've got a 10" f/6 1.6" thick mirror which I am making a cell for.
> I am planning a 6-point cell, using RTV. I am thinking of one of
> two paths:
> 
> 1. attach mirror directly to support plate with 6 blobs of RTV.
> 2. have 3 pivoting bars, each with 2 pads.  RTV the mirror to these
> pads. The bars would attach to the plate with swivel joints.
> 
> In either case, I would use edge supports .... either RTV or
> multiple points.  The pivoting bar aproach would be more work.
> Does it have any advantage?

I'd recommend a 3- or at most 4-point cell with Teflon (or some hard 
slick plastic) contact points.  They are very simple to make.  Leave a 
few thousandths of an inch for the mirror to move slightly, and you 
will have no problems with collimation or warping due to flexing or 
expanding/contracting substrates.

I have a 10" F/6.8 mirror 1.25" thick in a 4-pt cell built like this 
and it works very well and is easy to remove for cleaning/coating.

I have no glued-in mirrors (including secondaries) in any of my scopes.

	Mike Lockwood

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