A spectroscope is a device which measures the spectrum of light. Early spectroscopes were simply a prism with graduations marking wavelengths. Modern spectroscopes generally use a diffraction grating, a movable slit and some kind of photodetector, all automated and controlled by a computer. It breaks up the white light given off by stars and separates in to its chracteristic colors.
The spectroscope was invented by Gustav Robert Georg Kirchhoff and Robert Wilhelm Bunsen.
See also