Definitions for "Photometer"
An instrument for measuring the intensity of light, or, more especially, for comparing the relative intensities of different lights, or their relative illuminating power.
In astronomy, an instrument to measure the amount of light that reaches the telescope.
An instrument that measures illuminance.
A device so designed that it furnishes the ratio, or a function of theratio, of the radiant power of two electromagnetic beams. These two beams may be separated in time , space, or both.
Keywords:  aerosol, see
See: Aerosol Photometer