Spectral Efficiency of the SpectraSpan III Echelle Grating Spectrometer

The efficiency of an echelle grating spectrometer incorporating prism cross-dispersion is empirically evaluated over a broad wavelength range incorporating a large number of orders. A derived parameter, the spectrometer efficiency, proportional to the spectrometer luminosity, conveniently gauges dynamic features of the echelle efficiency. Characteristics of efficiency over broad wavelengths suggested by earlier work are clearly observed. The shift of blaze wavelength with decreasing order of diffraction, predicted in a recent model of echelle grating efficiency, is experimentally documented.