Lacaille I.11 (original) (raw)

Lacaille I.11 (NGC 6634)

During his journey to the Cape of Good Hope in 1751-52, Nicholas Louis de Lacaille observed this "nebulous" object in his 0.5-inch telescope, and included it in hisCatalog of Nebulae in the Southern Sky.

When Charles Messier looked for this object on July 27, 1764, he didn't find it. But when he observed again in 1780, he found both M69 and M70close to Lacaille's position. He thought that with M69, he had rediscovered Lac I.11. Many authors and historians of the Lacaille Catalog have since followed Messier with this identification.
However, as Glen Cozens of Australia has pointed out, this is probably not the case, for the following reasons:

M69 is much fainter than any other Lacaille object, and it is doubtful if that faint globular could have been seen with Lacaille's 1/2-inch aperture telescope.
Lacaille's position deviates from that of M69 by about 1.2 degrees. This is an untypically large error, and cannot be easily assigned to a copy or grid error.
There is a grouping of three stars of mag 8.3, 7.8, 8.7 at Lacaille's position, which in his modest instrument, could well have looked like a nebula. In his GC, John Herschel did not follow Messier's identification but assigned an own GC number to Lac I.11, GC 5076, which consequently found its way into the NGC (NGC 6634).

Thanks to Glen Cozens for contributing his identification!

Hartmut Frommert
Christine Kronberg
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Last Modification: July 20, 2011