Editing Optical spectrometer (section)

===Echelle spectrograph===
An [[echelle grating|echelle]]-based spectrograph uses two [[diffraction grating]]s, rotated 90 degrees with respect to each other and placed close to one another. Therefore, an entrance point and not a slit is used and a CCD-chip records the spectrum. Both gratings have a wide spacing, and one is [[Blazed grating|blazed]] so that only the first order is visible and the other is blazed with many higher orders visible, so a very fine spectrum is presented to the CCD.