Re: [ATM] polish time for 13 inch

["Mel Bartels" <mbartels@bbastrodesigns.com>]

> I take it when you press the lap into contact with the
> mirror in motion, you have the mirror on top. Is that
> correct?  


Yes


> How much pressure do you apply (with a 12
> inch mirror, for example)?  


During lap contact phase?  A few pounds from my hands pressed into the
mirror's back.


> What kind of stroke do you
> use when you are pressing (not figuring)?


Just move it to a new spot every few seconds.

> 
> When you are figuring with an oversized lap, how do you
> avoid changing the figure too much while you press the
> mirror with it moving?


Don't move it a lot - just enough to get perfect lap contact back.

 
> Is it possible to use the traditional wide-W parabolization
> strokes with an oversized lap, or do you have to
> preferentially microfacet the surface like you describe?


For large fast mirrors, a little bit of parabolization in the lap with cut
away pitch towards the edge is helpful in maintaining correction.  Then it's
not quite such an uphill battle to push more parabolization into the mirror.
For most amateur mirror sizes and focal ratios, it's not important to alter
the pitch lap.

Mel Bartels


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