Re: Optical comparators to find the null in Couder mask zones
- That's the hard way!
Use a simple video camera to display the Focault test on a monitor if you want but...
ALSO - hook the video signal to an O'Scope.
Then mask the mirror so that there is a narrow, horizontal band of the mirror exposed all the way across the center of the mirror, the O'Scope can then be used to very accurately MATCH the heights of the left and right side of the mirror (at the same time). You can actually watch the "Crest of the do-nut" travel across the mirror surface as you move the KE forward and back on the optical axis.
This is basically what the ROBO-Focault tester did years ago except the values were converted into numbers and software matched. A lot more fun to do it yourself...
> However, if you capture the image with a camera lens and project that
> image onto an old cathode ray tube, you now have a screen on which you
> can position two spot meters or two averaging meters. I'm not sure which
> would be better.