According to my reading of the above paragraph he sees:
outside-ring center --------------------------------------------------------------------- inside of focus: dark bright (rings less distinct) outside of focus: bright dark
Where as the pictures in Dick Suiter's book, Star Testing Astronomical Telescopes, clearly show:
undercorrected: outside-ring center --------------------------------------------------------------------- inside of focus: bright dark outside of focus: dark bright (rings less distinct)
overcorrected: outside-ring center --------------------------------------------------------------------- inside of focus: dark bright (rings less distinct) outside of focus: bright dark
So unless all the pictures in Suiter's book are backwards, or the description in the above paragraph is misleading, this mirror is OVERcorrected.
Section 10.6 of the book tells how to perform a test by measuring how far out of focus (on each side) the shadow of the secondary (or an artifical objstruction) appears. This test tells you if your under/over correction is more or less than 1/4 wave.
a 2:1 ratio of out-of-focus distances with a 33% obstruction is 1/4 wave correction error. Is this quanitative enough for the average user? I think so. I think this is particular test is the main new contribution of this book to the area. The rest of the book is good reference material.
Chuck