Dȳ-năm'e-ter, n.

n. [Fr. dynamètre, for dynamomètre, fr. Gr. δύναμις, power, and μέτρον, measure. Cf. DYNAMOMETER.] (Opt.) An instrument for determining the magnifying power of telescopes, consisting usually of a double-image micrometer applied to the eye-end of a telescope for measuring accurately the diameter of the image of the object-glass there formed; which measurement, compared with the actual diameter of the glass, gives the magnifying power.