The entrance slit width of a diffraction-grating spectrometer often limits the light-grasp or etendue of the instrument. The etendue may be increased by the use of a wide grating or mosaic, or one with a large blaze angle. However, those methods are not the only ones available. Further developments may use two or more gratings in arrangements other than a mosaic. These arrangements may use the different gratings in separate beams or consecutively in the same beam.