A test conceived by the Italian Vasco Ronchi in 1923. It uses a grating of fine parallel lines to test the deviation of a mirror from its correct figure. The grating is put in front of the eye after removing the eyepiece and pointing at a star. The lines should appear straight for a spherical mirror.
Foucault Test, Hartmann Test, Mirror Tests, Rayleigh Water Test, Terebizh Null Test
