If the instrument is designed to measure the spectrum on an absolute scale rather than a relative one, then it is typically called a spectrophotometer.

Modern spectroscopes generally use a diffraction grating, a movable slit, and some kind of photodetector, all automated and controlled by a computer.

Recent advances have seen increasing reliance of computational algorithms in a range of miniaturised spectrometers without diffraction gratings, for example, through the use of quantum dot-based filter arrays on to a CCD chip[3] or a series of photodetectors realised on a single nanostructure.

[4] Joseph von Fraunhofer developed the first modern spectroscope by combining a prism, diffraction slit and telescope in a manner that increased the spectral resolution and was reproducible in other laboratories.

[6][7] Kirchhoff and Bunsen's analysis also enabled a chemical explanation of stellar spectra, including Fraunhofer lines.

Particular light frequencies give rise to sharply defined bands on the scale which can be thought of as fingerprints.

In recent years, the electronic circuits built around the photomultiplier tube have replaced the camera, allowing real-time spectrographic analysis with far greater accuracy.

In many cases, the spectrum is displayed with the units left implied (such as "digital counts" per spectral channel).

Gemologists frequently use spectroscopes to determine the absorption spectra of gemstones, thereby allowing them to make inferences about what kind of gem they are examining.

[9] A gemologist may compare the absorption spectrum they observe with a catalogue of spectra for various gems to help narrow down the exact identity of the gem.A spectrograph is an instrument that separates light into its wavelengths and records the data.

[11] A spectrograph typically has a multi-channel detector system or camera that detects and records the spectrum of light.

In conventional spectrographs, a slit is inserted into the beam to limit the image extent in the dispersion direction.