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Reviewer: William Houston MacIntosh

Astronomy has always required mathematical calculations. Calculations determine when an eclipse will take place or when the first day of spring will occur. These and many other astronomical calculations have been known for centuries, but they are often time-consuming and tedious. Computers are ready-made to handle just such calculations, and the availability of low-cost personal computers now gives most amateur astronomers the ability to quickly and easily perform complex astronomical calculations. Duffett-Smith's book is a collection of 33 subroutines written in BASIC. The subroutines start out simple (converting between decimal hours or degrees and minutes or seconds) and become more complex (finding the position of a comet from parabolic elements). The book is an example of how wonderful a tool a computer and a few programs can be. With the subroutines in this book, the amateur astronomer can have more time to concentrate on the heavens and leave the earthly work of astronomical computations to the computer. Each of the subroutines appears in a separate chapter. The chapters start with a boldface sentence describing the purpose of the subroutine, which is followed by an in-depth discussion on why the calculations the subroutine performs are useful. The formulae that the subroutine uses are clearly shown, and a description of the subroutine itself follows the background discussion. The listing of the subroutine, a program calling the subroutine (called a handler by the author), and an example output complete a chapter. The program listings are clearly written and well commented. The author has done a good job of explaining the subroutines as well as why the calculations are needed. The subroutines and programs are well written and documented. They are also designed so that they are easily combined with each other, which they are in the more complex subroutines. The author worked at keeping the BASIC he used as generic as possible to be useful to as many people as possible. This volume is a good sourcebook for those amateur astronomers who are not afraid of some simple programming or for getting someonewho is familiar with programming interested in astronomy. It could also be useful to those who want more accuracy in their space games.