SpectrographA spectrograph is an instrument that separates incoming light according to its wavelength (like a spectrometer) and records the resulting spectrum in some detector.
In astronomy, spectrographs are located in a focus of a telescope. The first spectrographs used photographic paper as the detector. The star spectral classification and discovery of the main sequence, Hubble's law and the Hubble sequence were all made with spectrographs that used photographic paper.
Currently, spectrographs use detector adequate for the wavelegth range in which it operates, e.g. CCDs for optical and UV.