Cambridge University Press first published Deep-Sky Companions: The Messier Objects 15 or so years ago. It was the first in what is now a series of five Deep-Sky Companions volumes. The other books in the series are subtitled The Caldwell Objects, Hidden Treasures, The Secret Deep, and Southern Gems. Not only was The Messier Objects the first book in this series, but it was also the first deep-sky book I had ever written. As such it stands apart from the other volumes for several reasons.

First, many observers already had in their possession one or more books on the Messier objects, most notably The Messier Album by the late John H. Mallas and Evered Kreimer (Sky Publishing, Cambridge, MA, 1978), segments of which first appeared in Sky & Telescope magazine in the late 1960s, and Messier’s Nebulae and Star Clusters, 2nd edition, by the late Kenneth Glyn Jones (Cambridge University Press, 1991). Thus, I realized, my book would need a fresh approach.

For instance, to me, the most outstanding aspects of Glyn Jones’s book are the rich histories he presents on Messier and his contemporaries, as well as his summaries of historical observations of the “M” objects. Not wanting to duplicate this ef ort, I decided to minimize those aspects in my own book. I saw the Mallas and Kreimer book as having three strengths: (1) Kreimer’s beautiful photographs of the Messier objects taken through his 12 1/2-inch Cave rel ector from Prescott, Arizona; (2) Mallas’s pencil drawings of each M object as seen through a 4-inch f/15 Unitron refractor from his backyard in Covina, California; and (3) Harvard historian Owen Gingerich’s scholarly biography of Messier and his contemporary Pierre Méchain.