Re: Serious over correction (was ATM)

["Bill T." <twentiethwave@hotmail.com>]

pbal wrote:

>I am attempting to parabolize an 8" f 6.5 mirror.  I went way to far- the
Focalt test shows a .500" change from center to edge.  >The calculated
change should be about .125".  What is the appropriate stroke to get back to
a sphere?

Just start using the same broad "W" stroke you used to polish the mirror.
Occassionally swap mirror and lap positions.  This will take you back
towards a sphere, removing the over correction.

I recommend running a Foucault test after perhaps 20 or 30 minutes of
heading back towards a sphere.  More than once I have accidentally hit a
pretty good figure on the way back from over correction.

Bill T.