Re: [ATM] Figuring advice

[Mike Lockwood <melockwo@uiuc.edu>]

Douglas,

Douglas Arion wrote:
> I'm working on a 6" f/4.5 primary, and its been hard to get
> all the zones behaving well...so, when does it make more
> sense to take it back to spherical and start again, or to
> continue futzing (sp?) with the figure to try to bring it
> around? I'm worried it may not be 'smooth' in the latter
> case. Suggestions? At the moment, the center depth is about
> right, but too flat, and the edge is high...

Are you using the Focault test?
Are you using a computer program (TEX, FigureXP, Sixtests) to analyze 
your Focault data?

If so, post your data (ROC - radius of curvature, mask radii, zonal 
readings) to the list.  You can adjust the ROC in the software, and 
then the edge will become OK, and the center will appear high.  Then 
you can work areas of the mirror inside the edge, which is much easier.

If you mirror is zony, (alternating high and low spots), then normal 
strokes may help smooth it out.  It's good practice to smooth the 
mirror with normal strokes and then apply more parabolizing strokes to 
add the correction back in.

One more question - how long does it take the channels in your pitch 
lap to close up when you are doing normal polishing?

	Mike Lockwood

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