An echelle grating with 316 grooves/mm and a 63° blaze angle is compared with a 3600-groove/mm holographic grating. The scattered light and resolution of the 10- × 20-cm gratings are photoelectrically evaluated in a 3-m spectrometer optimized to eliminate coma and baffled to minimize instrumental scattered light. Both gratings are ghost-free, but the holographic grating has substantially lower scattered light for test lines near 4000 Å and yields improved stray light rejection within absorption lines. It also exhibits slightly higher resolution. The throughput of the spectrometer with the holographic grating is about 5 times higher than the equivalent combination of spectrometer, echelle grating, and predisperser.
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