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Old 13-01-2015, 08:26 AM
cfranks (Charles)
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Join Date: Feb 2008
Location: Tungkillo, South Australia
Posts: 599
If the sagitta reduced then you are grinding the edge away. In my day I only used the W stroke to parabolize the mirror after polishing. Grinding was mostly centre over centre with the odd, random, variation to avoid zones. Grinding and polishing a spherical surface first is very easy and can be tested very accurately. Then I used the W stroke.

Charles
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