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Posted by Robert May on November 17, 2001 22:18:57 UTC

When the shadow follows the KE then you have a longer ROC than the distance from the KE to the mirror. This means that you have a small hole in the middle of the mirror.
Since you're on pads, change the stroke length and width of the W and that hole will change and may even go away. You might want to measure the difference in ROC of the center area just to play with the tester and familiarize yourself with the usage of the thing.
Pads can leave the surface with a lot of different zones but they are all short in width so the actual surface really isn't that far off from where it should be.

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