The spectrometer comprises at least a first optical path for a beam of electromagnetic radiation, along which the following are set: a beam-entry slit (1) for an incoming beam; a collimator (5) comprising a convergent spherical mirror for collimation of the incoming beam; a first dispersor (9) for dispersion of the beam into its chromatic components; a first focusing system (19); and a first detector (21) which receives the beam dispersed and focused by said first focusing system. Set along the first optical path there is set at least one first aspherical corrector element (7; 17) comprising an aspherical mirror for correction of spherical aberration.