Re: [ATM] Posible variation on the Cassegrain secondary

["Bob May" <bobmay@nethere.com>]

Actually, the figuring for a typical mirror will have the
difference between a center dig vs. an edge dig parabola well
within a percent of the ROC of each other.  You're looking at a
difference in ROC of about a tenth of an inch.  Generally the ROC
control needs to be done as the grinding happens.  Once you get
to start polishing, generally a change of a half inch is a big
change in ROC and takes a while to do.  Persistant chasing of the
turned edge by incorrect polishing is the biggest causer of a
shorter ROC as the polisher proceeds down the wrong path of
correction.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

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