What is a reflecting telescope, part of which is made to rotate eccentrically, so as to produce a ringlike image of a star, instead of a point; -- used in studying the scintillation of the stars called?

chromatoscope — A reflecting telescope, part of which is made to rotate eccentrically, so as to produce a ringlike image of a star, instead of a point; -- used in studying the scintillation of the stars. (Webster's 1913.)

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