Book excerpt: This new edition of Allen's classic "Astrophysical Quantities" belongs on every astronomer's bookshelf. It has been thoroughly revised and updated by a team of internationally renowned team of astronomers and astrophysicists. Topics covered include: * General constants and units * Atoms, molecules, and spectra * Observational astronomy at all wavelengths from radio to gamma-rays, and neutrinos * Planetary astronomy: Earth, planets and satellites, and solar system small bodies * The Sun, normal stars, and stars with special characteristics * Cataclysmic and symbiotic variables, supernovae * Theoretical stellar evolution * Circumstellar and interstellar material * Star clusters, galaxies, quasars, and active galactic nuclei * Clusters and groups of galaxies * Cosmology