A wideband spectrograph apparatus includes a first spectrograph assembly and one or more subsequent spectrograph assemblies. Each subsequent spectrograph assembly is optically coupled to a previous spectrograph assembly and is configured to receive a cascading beam from one or more dispersion elements of the previous spectrograph assembly. The first spectrograph assembly is configured for detecting illumination in a first wavelength range and the one or more subsequent spectrograph assemblies are configured for detecting illumination in wavelength ranges different from the first or any previous wavelength ranges to provide simultaneous sampling of different spectral portions of an input beam.