Pressure-Scanned Echelle Grating plus Fabry-Perot Stellar Spectrophotometer.
A photoelectric stellar spectrophotometer, with 0.3-A resolution, for use near Halpha (6563 A) is described. A Fabry-Perot etalon and an echelle grating are simultaneously pressure-scanned. The Fabry-Perot can be bypassed and the grating system used alone to obtain narrow-band (4.89-A) Halpha indices, in which case the pressure system allows the necessary radial velocity corrections to be made conveniently.
Caplan
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