Optical emission spectrometer easy to adjust

The invention relates to an easy-to-tune optical emission spectrometer (1) and a method (100) for establishing and operating such a spectrometer (1), the spectrometer (1) comprising a plasma holder (2) for establishing a luminescent plasma from a sample material, and an optical system (3) for measuring a spectrum of light (L) emitted by the plasma, the spectrum being a characteristic of the sample material, wherein the optical system (3) comprises at least one light entry aperture (31), at least one diffraction grating (32) for separating light (L) from the plasma (A) and one or more detectors (33) for measuring the spectrum of the light (L), wherein the plasma holder (2) and the optical system (3) are mounted directly and fixedly on a plasma holder flange (2B) and an optical system flange (3B), respectively, which are directly and fixedly connected to each other, and wherein the optical emission spectrometer (1) further comprises an analysis unit (34) adapted to analyze the measured spectrum, and compensatin