High-dispersion astronomical spectroscopy with holographic and ruled diffraction gratings.
Holographic gratings cause much less stray light and spectral degradation than classically ruled gratings. Their high groove densities enable high dispersion in first diffraction order and a high spectrograph through-put comparable to the best echelles. Their lower reflective efficiency is compensated by the avoidance of cross dispersers, enabling efficient high-fidelity spectroscopy with single-pass spectrographs. Instrumental profiles of the ESO coudé spectrograph with large holographic and ruled gratings have been studied in detail, and their effects on astronomical spectra are discussed and compared to those of other instruments.
Dravins
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