From: "Vladimir Galogaza" 
To: "ATM shore" 
Reply-To: "Vladimir Galogaza" 


When KE cuts the focus of particular zone,  left and right part of this
zone change intensity in synchrony. This is sometimes called "blinking
method". If the KE is on the optical axis  it can never be at the true
focus for any zone except mirror center. true focus is at the caustic which
is not at the optical axis. With KE on the optical axis determination of
the zone is less precise than if KE looks for zone at caustic. If this is
so in actual practice of amateur mirror makers remains to be documented.
But robotic determination, I presume,  will be inherently more precise if
performed on caustic. I do not know how much more complicated that will be
than present method, e. g. RoboFoucault from James Lerch. It would be
interesting to have James opinion on this.

Vladimir.

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