A. E. L. Davis’s (deceased) doctoral thesis (Imperial College, University of London, 1981) was about the mathematics of Kepler’s New Astronomy (Astronomia nova, 1609). This research led on to about fifty years of publishing papers on various aspects of Kepler’s mathematical astronomy, in particular on his derivation of his laws of planetary motion and specifically on the intricate iterative procedures that led him to decide the orbit of Mars was elliptical, as well as some more general papers on aspects of the history of mathematics and the study of conic sections. J. V. Field became interested in Kepler in the early 1970s while helping Arthur Beer with work on the Kepler volume of Vistas in Astronomy (1975), eventually writing a doctoral thesis on Kepler’s cosmology (Imperial College, University of London, 1981), collaborating with Eric Aiton and Alistair Duncan in the translation of Kepler’s Harmony of the World (Harmonice mundi, 1619, translation published 1997) and writing extensively on various parts of Kepler’s work—though firmly leaving his mathematical astronomy in the expert hands of A. E. L. Davis. T. J. Mahoney is a scientific editor at the Instituto de Astrofísica de Canarias, where he researches on the structure of the Inner Galaxy, and the life and work of Johannes Kepler. He has edited volumes on a number of astrophysical topics. He chaired the former Johannes Kepler Working Group of the International Astronomical Union and the Johannes Kepler Task Group of the 2009 International Year of Astronomy.