An optical instrument that produces a spectrum for visual observation. The first such instrument was made by Robert Bunsen; in its simplest form it consists of a hollow tube with a slit at one end by which the light enters and a collimating lens at the other end to produce a parallel beam, a prism to disperse the light, and a telescope for viewing the spectrum. In the spectrograph, the spectroscope is provided with a camera to record the spectrum.
For a broad range of spectroscopic work, from the ultraviolet to the infrared, a diffraction grating is used instead of a prism. See also spectrometer.