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This is a Ronchigram of a 10" mirror using autocollimation. The mirror performed quite well. A slight depression near the center disturbed the shadow breakout in the star test and there is a sharp, very narrow TDE that is not visible due to the size of my test flat (9.75"). It likely would take a grating with more lines per inch to be visible in any case and the planetary images were well detailed with good contrast. Recall that in autocollimation with a test flat, the light bounces off the mirror twice and the errors are doubled compared the same test applied to a star.