Practical astronomy with your calculator has been written for those who wish to calculate the positions and visual aspects of the major heavenly bodies and important phenomena such as eclipses, either for practical purposes or simply because they enjoy making predictions. I have tried to cut a path through the complexities and difficult concepts of rigorous mathematics, taking account only of those factors which are essential to each calculation and ignoring corrections for this and that, necessary for the very precise predictions of astronomical phenomena. My simple methods are usually sufficient for all but the most exacting amateur astronomer, but they should not be used for navigational purposes. For example, the times of sunrise and sunset can be determined to within one minute and the position of the Moon to within one fifth of a degree.

The second edition included much more material in response to letters and requests from readers of the first edition. I also corrected many errors. This new third edition continues the same process. You will find four new sections on generalised coordinate transformations, nutation, aberration, and selenographic coordinates; I have improved the sunrise/set and moonrise/set Calculations so that they work properly everywhere in the world; the section on precession now contains a rigorous method of calculating precession as well as the approximate one of previous editions; I have taken account of the new J2000 astronomical system where appropriate, and have updated the material by assuming the epoch 1990 January 0.0 as the starting point for calculations; and I have corrected mistakes and clarified obscurities wherever I have been aware of them in the second edition.