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 his
Catalog 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 M70
close 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:
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).
- 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
- 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
Thanks to Glen Cozens for contributing his identification!
NGC Online data for NGC 6634
The "missing" Lacaille objects
Last Modification: July 20, 2011