Compact, solar spectrometer with sub-half angstrom resolution, faint-light compensation, and infrared and ultraviolet suppression

摘要

A compact, grating spectrometer (1A) particularly adapted for visual observation of the sun's spectrum, from the Calcium K line to the Fraunhofer B line, at very high dispersion. The numerical aperture of the spectrometer's collimating mirror is intentionally mismatched to the numerical aperture of the spectrometer's light-input device in order to exploit, by means of the exceedingly narrow width of the spectrometer's entrance slit (110), the high degree of coherence of the central region of the Airy disk formed by the light-input device. The resulting Fraunhofer diffraction illuminates totally, or nearly totally, the collimating mirror throughout the K-B interval. The human eye's dynamic range is compensated to maintain resolution at the lowest, light levels of the K-B interval. UV spill is suppressed. Both input-optics and slit are shielded against differential heating.