Revised list of Sir William Herschel's Fields of Diffuse Nebulosity

A. Latusseck

William Herschel's catalogue of more than 2500 nonstellar celestial objects is without doubt one of the great astronomical achievements of this exceptional astronomer. Largely unknown, however, is a list containing fifty-two fields of extensive nebulosity, which Herschel published in 1811 as a supporting argument to his nebular hypothesis (Herschel, 1811: 275-276), all of which were observed as a by-product of his sweeps between 1783 and 1802. For the purpose of a final revision of Herschel's objects, his sister Caroline's copies of the eight observing books containing the results of his decade-long sweeps (Herschel, Herschel and Herschel, 2004) were analyzed. As a result, a number of errors and inaccuracies were found and corrected. Furthermore, the terminology used to describe the observed nebulosities--which differed widely from that used by Herschel to describe non-stellar objects in his better-known catalogues of nebulae--was investigated in order to obtain a clearer impression of the appearance of Herschel's objects. The resulting revised list, being one principal result of the review of Herschel's list of fifty-two nebulosities, contains corrected physical information on each of the nebulosities. It further gives estimates on the reliability of Herschel's observations and finally summarizes all of the noticed peculiarities in a separate column.