Book Review: Herschel's Nebulae: The Complete Guide to the Herschel Objects: Sir William Herschel's Star Clusters, Nebulae and Galaxies

Abstract

HERSCHEL'S NEBULAE The Complete Guide to the Herschel Objects: Sir William Herschel's Star Clusters, Nebulae and Galaxies. Mark Bratton (Cambridge University Press, Cambridge, 2011). Pp. viii + 584. £45/$70. ISBN 978-0-521-76892-4.Mark Bratton is a Canadian amateur observer with a mission, now triumphantly accomplished: to observe every one of the two-and-a-half thousand nebulae and clusters Usted by William Herschel in his catalogues of 1786, 1789 and 1802. Fittingly, the task has taken him two decades, the same time that Herschel needed to assemble his catalogues in the first place.The bulk of this remarkable book consists of data on these objects, assembled by constellation, and laid out on pages with three columns, with numerous illustrations. For each object we are given the basic facts, along with the appearance of the object in photographs, and its appearance visually where this is significantly different. The book will become the reference work for any amateur observers minded to follow in Bratton's footsteps.For a review in this journal is appropriate to focus - if somewhat unfairly - on the first thirty pages of historical introduction. Unfortunately, as the Bibliography shows, Bratton is unfamiliar with most of the recent historical work on Herschel, and so depends too much on a book the reviewer wrote half-a-century ago, when the Herschel archive was still in a wooden box. It was not then known that Herschel believed that in his early years as an observer he had himself observed frequent changes in the Orion Nebula, which therefore could not be a distant star system but must be formed of 'true nebulosity'. The question of whether or not true nebulosity existed then became central to Herschel 's programme of sweeping for nebulae, and to his construction of a monster 40-ft reflector with huge 'light-gathering power' ; and his answer was in turn, yes, no, and yes. Once the affirmative answer was established beyond question, the programme of sweeps (and the 40-ft reflector) lost their purpose, and so was by no means curiously (p. 29) that the sweeps thereafter became rare.Bratton remarks that it is unfortunate that Herschel 's contemporaries did not try to verify his discoveries independently while he was still alive (p. vii), but the answer was given by his son John seven years after William's death: nobody else can see them.On pp. 25-6 Bratton gives a correct account of Herschel's method of sweeping, whereby the 20-ft was used as a transit instrument and so kept facing exactly south, but constantly raised and lowered by a workman through an angle of 2° or more, so that a horizontal strip of sky of this width could be examined as passed across the meridian. Yet Bratton opens his book with an imagined scenario (p. …