Textbook in PDF format

Astrophysics is often –with some justification – regarded as incomprehensible without the use of higher mathematics. Consequently, many amateur astronomers miss out on some of the most fascinating aspects of the subject. Astrophysics Is Easy! cuts through the difficult mathematics and explains the basics of astrophysics in accessible terms. Using nothing more than plain arithmetic and simple examples, the workings of the universe are outlined in a straightforward yet detailed and easy-to-grasp manner.
Following on the success of the first and second editions, this fully updated third edition covers the significant changes in astrophysics theories and research that have occurred in the last five years, including new material on: exomoons, exocomets and exoasteroids; Special and General Relativity; gravitational waves, their origins and detection; telescope optics; black hole astrophysics; and more.
For each topic under discussion, an observing list is included so that observers can actually see for themselves the concepts presented – stars of the spectral sequence, nebulae, galaxies, even black holes. The book also features in-text, nonmathematical questions and end-of-chapter problems – all with their accompanying solutions – to help readers discuss and digest the material