Multi-slit spectrograph and H alpha Doppler system

Description of the design and operation of a multiple-entrance-slit spectrograph, built for time-lapse photography of the spectra of flares and other transient solar phenomena. This spectrograph employs narrow-band filters to limit the wavelength range of the spectrograph to a few angstroms centered at H-alpha or other spectral lines. A polarizing beamsplitter, prior to the slits, provides a prefiltered second solar image to a narrow band H-alpha Doppler filter for simultaneous photography in the wings of the H-alpha line. The spectrograph and the H-alpha Doppler system constitute a flexible instrument in which components may be substituted to achieve different passband widths, image scales, dispersions, and corresponding numbers and spacings of adjacent spectra at a selected wavelength.