Re: [ATM] Fringe testing Dall Kirkham secondary

["Rod Brackenridge" <rjbr@lycos.com>]

Thanks to everyone with their explanations.  As suggested I have spent some time (about 20 mins total) working with the tool on top of the convex secondary.  There has not been any change to the bulls eye pattern.  The secondary is not quite fully polished - some faint mistiness still visible from fine grinding.  I have been using 1/3 centre over centre strokes and W strokes.  Since the surface is near spherical, I didn't want to risk a turned edge with longer strokes.  

If there continues to be no change to the bulls eye pattern I thought I would take Jarvis' advice and call it finished when the surface is fully polished.  Adjusting the space between primary and secondary is no problem.

Rod.


> 
> I only just picked up on this thread having missed the beginning.  Since
> the desired curve for the Dall-Kirkham secondary is a spherical surface
> the evenly spaced rings are good.  A small difference (Waves) in the
> secondary radius from the test plate should be insignificant in the final
> system.  If you've got a good sphere, readjust the spacing between
> primary and secondary slightly and don't worry too much.
> 
> Jarvis Krumbein
> 
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Kerrie, Rod, Sarah & David
%0

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