Nicolas-Louis de La Caille, James Dunlop and John Herschel: An analysis of the First Three Catalogues of Southern Star Clusters and Nebulae

Abstract

“If men like [John] Herschel are to spend the best years of their lives in recording for the benefit of a remote posterity the actual state of the heavens…what a galling discovery to find amongst their own contemporaries men [James Dunlop] who … from carelessness and culpable apathy hand down to posterity a mass of errors …[so] that four hundred objects out of six hundred could not be identified in any manner … with a telescope seven times more powerful than that stated to have been used!”4 The denigration of James Dunlop and his catalogue of 629 southern nebulae and clusters produced in 1826 originated with John Herschel and was continued by others of his day. Was this criticism justified? Was James Dunlop guilty of “carelessness and culpable apathy”? Were there “four hundred objects out of six hundred” which could not be identified, and if so, was there an explanation for this large shortfall? This question led to a search within Dunlop’s 1826 catalogue to rediscover, if possible, some of the missing objects and to reinstate Dunlop, if justified, as a bona fide astronomer. In doing this, Dunlop’s personal background, education and experience became relevant, as did a comparison with the catalogue of 42 southern nebulae and clusters produced by Nicolas-Louis de La Caille in 1751-2, and the 1834-8 catalogue of 1708 southern nebulae and clusters by John Herschel, who found the Dunlop catalogue so galling.