The advent of modern techniques of observation in the world ofamateur astronomers increases their potential to participate efficentlyto scientific programs. In particular, spectrography is a new, quicklydeveloping tool for amateur astronomers. Moreover, amateur astronomershave more and more possibilities to access telescopes with diametersabove 50 cm, either in professional observatories or belonging toassociations.These improvements allow professional and amateurs to undertakefruitful collaborations and common meetings. This book collects thelectures given by professional for amateur astronomers during a CNRSschool. It focuses on spectroscopy, a budding domain for amateursalready extensively used by professionals.Basic principles of spectroscopy are described in a clear and preciseway and applications to the Sun, Be stars, nebulae, and comets aresuccessively exposed. A chapter is dedicated to the analysis ofspectral data, to put practical spectroscopy within reach of amateurastronomers.