échelle spectrograph

An échelle spectrograph is a spectrograph that uses an échelle grating to achieve high spectral resolution and wide wavelength coverage. The overlapping spectra produced by the grating are separated by a prism or a grism before reaching the detector. The sensitivity brought to modern échelle spectrographs by CCD detectors has made them indispensable in such fields as astroseismology and extrasolar planet searches.