SPECTROSCOPIC INSTRUMENTATION FROM THE USER'S POINT OF VIEW

Experimentation with a 5-meter vacuum Ebert Fastie spectrograph (with the basic design by W. G. Fastie and constructed by the Jarrell-Ash Co.) is reported; the experimentation was into very high resolution, particularly in the vacuum ultraviolet. Orders were separated by an order sorter with cross dispersion: above 2000 A a quartz prism was used and below, a grating with a concave mirror. Both order sorters performed adequately. A 600 000 resolving power was achieved. The spectrograph apparently will give in the vacuum UV above 1000 A a resolution and wave number accuracy obtainable only for the visible and adjacent regions. Except for very special light sources, resolution and wave number accuracy are determined by actual line width rather than by performance of the spectrograph.
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