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TDE/TUE

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Posted by Robert May on January 21, 2002 19:40:27 UTC

The direction of the lines depends upon the side of focus you are on. I generally prefer to do the Foucault test as you get to see the numbers of where the ROC is relative to the center of the mirror and you get quantitive results - no guessing if the curve radius of the lines are right but rather actual numbers of where the ROC is.
On a basically parabolic mirror, when the ends of the lines curve the same way as the lines, that's TDE while a hook the other way is TUE. Remember that with the parabolic mirror, the ROC is constantly increasing with the distance from the center of the mirror.

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