The Collaborative International Dictionary of English v.0.48:

Cyanometer \Cy`a*nom"e*ter\ (s?`?-n?m"?-t?r), n. [Gr. ky`anos a
   dark blue substance + -meter: cf. F. cyanom[`e]tre.]
   An instrument for measuring degress of blueness.
   [1913 Webster]