A spectral analytical unit for acting on a parallel light bundle having different wavelengths. The spectral analytical unit includes a diffraction grating on which the light bundle falls, the diffraction grating splitting the different wavelengths through diffraction in first spectral directions defining a light bundle diffraction order 1 without recycle, and the diffraction grating bending the light bundle in second directions defining a light bundle diffraction order 0 without recycle, a detector line made up of a plurality of elements, optics for focusing the split light bundle diffraction order 1 without recycle on the detector line, evaluation electronics connected to the detector line for obtaining data related to a created spectrum, and a deflecting device wherein the diffraction order 0 light bundle without recycle meets on the deflecting device which is so directed and positioned that this light bundle falls on the diffraction grating thereby creating a reflected diffraction order 1 light bundle with first recycle and a reflected diffraction order 0 light bundle with first recycle whereby the diffraction order 1 without recycle and the reflected diffraction order 1 light bundle with first recycle each of a part wavelength range are impressed through the optics on a single element of the detector line.