Astronomical Spectroscopy

Spectroscopy is one of the most important tools that an astronomer has forstudying the universe. This chapter begins by discussing the basics, including thedifferent types of optical spectrographs, with extension to the ultraviolet and thenear-infrared. Emphasis is given to the fundamentals of how spectrographs areused, and the trade-offs involved in designing an observational experiment. It thencovers observing and reduction techniques, noting that some of the standardpractices of flat-fielding often actually degrade the quality of the data rather thanimprove it. Although the focus is on point sources, spatially resolved spectroscopyof extended sources is also briefly discussed. Discussion of differential extinction,the impact of crowding, multi-object techniques, optimal extractions,flat-fielding considerations, and determining radial velocities and velocitydispersions provide the spectroscopist with the fundamentals needed to obtainthe best data. Finally the chapter combines the previous material byproviding some examples of real-life observing experiences with several typicalinstruments.