Astrospectroscopy

Since 1814 when Joseph von Fraunhofer discovered the appearance of dark lines in the solar spectrum, spectroscopy became more and more important in astronomy. Nowadays, not only professionals have access to this powerful technique, it is also common to have spectroscopic instruments in amateur astronomy. As conventional grating and prism spectrographs are used since many years, echelle spectroscopy is a rather new technique. The main difference in echelle spectroscopy is to use a special kind of diffraction grating of which the rulings are much further apart than usual. Echelle gratings are specially designed to operate at very high orders e.g. 25-65 and large blaze angles. This leads to spectra of very high dispersion, separated into many diffraction orders. Since higher orders tend to overlap, a cross-dispersing element (prism or grating) is necessary to separate the single orders.