Do you have your own computer? And do you wish to use it for predicting astronomical phenomena such as the time of moonrise or the circumstances of the next eclipse? If so, this book may help you. It provides a kit of parts, a set of building blocks, to write complex programs in astronomy tailored to your own needs. Each building block is in the form of a subroutine, written in BASIC, which performs a well-defined function. There are 33 such routines in all which can link together in any combination. They cover most of the problems likely to be tackled by the amateur astronomer, ranging from very simple tasks like converting between decimal hours and hours, minutes, and seconds, to complex procedures for deducing the set of orbital elements which is consistent with the observed movement of a minor planet or comet through the heavens. It is possible that your particular requirement may be covered directly by a subroutine as it stands, for example, the calculation of the position of the Moon. You can then enter it from the keyboard or copy it from disk+ and run it with its supplied handling program. Or it may be that you have a much more demanding task, needing the results of several routines together to get the answer. Suppose, for instance, that you wished to predict the time of rising of a newly-discovered comet in Hawaii on the 27th August this year.