Geometrical optic techniques are used to analyze and compare the symmetrical spherical mirror to the unsymmetrical spherical-mirror Czerny–Turner spectrometer. The aberration problems due to diffraction from the grating are analyzed and methods of partial correction of the aberrations are derived. The flux and resolution advantage of gratings with high blaze angles used in the unsymmetrical spherical-mirror Czerny–Turner is shown. A design and ray tracing routine employing a digital computer is utilized to illustrate the geometric effects of the diffraction grating and the partial corrective measures. Slit curvature is analyzed numerically and some general results are abstracted from the numerical data. It may be inferred from the results of theory and numerical calculations that the unsymmetrical Czerny–Turner spectrometer using two spherical mirrors can be made superior to a similar symmetrical Czerny–Turner spectrometer. A comparison of luminosity is made between the Czerny–Turner spectrometer, utilizing a high blaze grating, and various interf erometric and modulating spectrometers and it is shown that the luminosity of the Czerny–Turner spectrometer is comparable or superior.
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