Schwarzschild spectrometer

This is a proposal and description of a new spectrometer based on the Schwarzschild optical system. The proposed design contains two Schwarzschild optical systems. Light diverging from the spectrometer entrance slit is collimated by the first one; the collimated light beam hits a planar diffraction grating and the light dispersed from the grating is focused by the second system, which is concentric with the first. A very simple procedure obtains designs that are anastigmatic for the center of the slit and for a particular wavelength. A specific example shows the performance of this type of spectrometer.