Re: [ATM] 9pt cell for 16.5 1"-thin quartz mirror?

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

William,





> Please help me figure out how to mount my 16.5" f/4.5, 1"-thin
> quartz mirror.  I don't know how good the mirror is.

Plop, assuming fused silica, says 5 nm RMS for 6 points at 0.6 of the
radius - this is in general better than a 9 point cell, and ought to be
adequate if without much safety margin.

But why not start by using the cell as is, try some star-testing and see if
a fix is really needed?

good luck,

Nils Olof
>
> I have a second-hand Starsplitter mirror box with a so-so 9pt
> cell for a 16" normal-thickness mirror.  I can put pads (or
> glue my mirror) at the corners of a 7"-radius/per-side hexagon,
> geometrically speaking.  The inner three points will then be
> at a radius of about 2.5", with the three (pre-existing) pivot
> points at a radius of 4 13/16".  The pivot "points" are simply
> loose bolts and somewhat sloppy (one of them especially so).
>
> Would this configuration "suffice" or must I look for an
> alternative?
>
> (I have very little time and no metal-working tools other than
> a Dremel.  I do have a simple and somewhat novel design in mind
> for a 6pt cell if someone could make it for me :-)
>
> Your recommendations are very much appreciated,
>
> -- William (Saratoga, CA)
>
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>


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