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F/15 Vs. F/9 Focal Ratios

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Posted by Robert May on April 6, 2001 18:13:39 UTC

The curvature for the F15 will be less than the F9 that I have and as a result, should be a lot smoother. Mine has a very zoney appearance (it's still better than 1/4 wave but a Ronchi test shows the zones quite well) on the Ronchi test on a star and thus, it's not as good as it could be.

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