An optical system comprising: - an entrance aperture for entering primary light to be analyzed forming a primary light beam serving as a primary light feed, where the primary light beam contains a first, lower wavelength range and a second, higher wavelength range, - a grating for spectral dispersion of the primary light beam into a first fan of diffracted light within the first wavelength range and a primary zero order light beam, - a mirror element suitably positioned to reflect the primary zero order light beam by 180 degrees forming a secondary light beam serving as a secondary light feed to the grating where the secondary light beam is dispersed into a second fan of diffracted light within the second wavelength range and a secondary zero order light beam, - a detector arrangement comprising multiple detectors, characterized in that it further comprises - an absorber element movably mounted to be reversibly placed within the primary zero order light beam between the grating and the mirror element, and - a filter element movably mounted to be reversibly placed within the primary light beam between the entrance aperture and the grating, wherein the detector arrangement is adapted to measure the first fan of diffracted light in case of the absorber element being placed within the primary zero order light beam to absorb the primary zero order light and the filter element being positioned outside the primary light beam, and to measure the second fan of diffracted light in case of the filter element being arranged within the primary light beam to filter out the first wavelength range out of the primary light beam and the absorber element being positioned outside the primary zero order light beam. - an entrance aperture for entering primary light to be analyzed forming a primary light beam serving as a primary light feed, where the primary light beam contains a first, lower wavelength range and a second, higher wavelength range, - a grating for spectral dispersion of the primary light beam into a first fan of diffracted light within the first wavelength range and a primary zero order light beam, - a mirror element suitably positioned to reflect the primary zero order light beam by 180 degrees forming a secondary light beam serving as a secondary light feed to the grating where the secondary light beam is dispersed into a second fan of diffracted light within the second wavelength range and a secondary zero order light beam, - a detector arrangement comprising multiple detectors, - an absorber element movably mounted to be reversibly placed within the primary zero order light beam between the grating and the mirror element, and - a filter element movably mounted to be reversibly placed within the primary light beam between the entrance aperture and the grating, wherein the detector arrangement is adapted to measure the first fan of diffracted light in case of the absorber element being placed within the primary zero order light beam to absorb the primary zero order light and the filter element being positioned outside the primary light beam, and to measure the second fan of diffracted light in case of the filter element being arranged within the primary light beam to filter out the first wavelength range out of the primary light beam and the absorber element being positioned outside the primary zero order light beam. primary light beam between the entrance aperture and the grating, wherein the detector arrangement is adapted to measure the first fan of diffracted light in case of the absorber element being placed within the primary zero order light beam to absorb the primary zero order light and the filter element being positioned outside the primary light beam, and to measure the second fan of diffracted light in case of the filter element being arranged within the primary light beam to filter out the first wavelength range out of the primary light beam and the absorber element being positioned outside the primary zero order light beam.