Ronchi test
McGraw-Hill Science & Technology Dictionary:
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Ronchi test
(′raŋ·kē ′test)
(optics) An improvement on the Foucault knife-edge test for testing curved mirrors, in which the knife edge is replaced with a transmission grating with 15-80 lines per centimeter, and the pinhole source is replaced with a slit or a section of the same grating.
Wiley Book of Astronomy:
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Ronchi test
An efficient way of checking the shape of a telescope mirror. Conceived by the Italian optician Vasco Ronchi (1897–1988) in 1923, it is based on the Foucault knife-edge test but instead of a straight edge it uses a small diffraction grating with 20 to 40 lines per millimeter. The grating is put in front of the eye after removing the eyepiece and pointing at a star. Any curvature of the lines indicates deviations from a spherical mirror.
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McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.
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