Re: [ATM] Ain't got no shperometer

[ArtfulBodger <artfulbodger@earthlink.net>]

David Adams wrote:

> By moving the sphereometer around you can 
> find zones with different radii of curvature 
> which would provide you some information
> on lack of sphericity....  

Yeah, that's what I had in mind: put the spherometer at one edge, 
then slide it right across the diameter of the mirror; and if you can 
do that without the needle moving, then boom! -- you're spherical. 
To the limit of the spherometer's accuracy, of course.  The one I 
borrow on Saturdays reads tenths.

I don't use it for figuring sagitta & focal length.  For that I use a 
bar-type sagittometer (is that a word?) whose dial reads .001", or if 
that's not available I just use a straight-edge and a set of feeler 
gauges.

> I have only ever done one mirror (a 16.5 inch f 5.68) which I expect to
> add the final finishing touches tomorrow night and then off to have it
> alumninized.   I AM SO JAZZED!  

Congratulations, David!  16.5" for a first mirror -- that's big.  A 
real accomplishment.  Well done.

Pete

-- 
Artful Bodger
http://www.artfulbodger.net
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