'The first two editions of this textbook have received well-deserved high acclaims, and this - the third edition - deserves no less. Its explanations of the whole gamut of atomic and molecular spectroscopy provide a solid grasp of the theory as well as how to understand such spectra in practice. It thus makes an ideal companion to books that start from the observational aspect of spectroscopy, whether in the lab or at the telescope ... This new edition of TennysonaEURO (TM)s book ought to be in the library of every astronomical department.'The Observatory Magazine'It closely follows the course given to third year UCL undergraduates, and the worked examples have surely been tested on students ... The last two chapters serve as an effective appendix on more specialised topics in atomic and molecular theory.'Contemporary PhysicsThe third edition of Astronomical Spectroscopy examines the physics necessary to understand and interpret astronomical spectra. It offers a step-by-step guide to the atomic and molecular physics involved in providing astronomical spectra starting from the relatively simple hydrogen atom and working its way to the spectroscopy of small molecules.Based on UCL course material, this book uses actual astronomical spectra to illustrate the theoretical aspects of the book to give the reader a feel for such spectra as well as an awareness of what information can be retrieved from them. It also provides comprehensive exercises, with answers given, to aid understanding.