The "missing" Lacaille objects

Ten of the 42 entries in Lacaille's Catalog of Nebulae in the Southern Skies are not commonly recognized as Deepsky Objects. Glen Cozens (gc) has investigated Lacaille's positions/entries for these objects, which in turn caused the present author to have a closer look on these identifications and the result.

This work is still in flow, so the preliminary material given here should be taken with the appropriate care.

Independently, Ronald Stoyan (rs) of Germany has taken a new effort to identify the missing Lacaille objects.

Please send me any comments, corrections, errata and contributions.

Lac I.13 (NGC 6777, GC 4484; double star): Two stars mag 8.0 and 8.3 [gc] - strange that Lacaille found it resembling the preceding, Lac. I.12 = M22 [hf]. Formerly, induced by this description, Owen Gingerich (1960) had proposed this object might be identified with globular cluster NGC 6752, but this globular is over 12 deg away from Lacaille's position [rs].
Lac I.11 (NGC 6634, GC 5076; 3 stars): Three stars mag 8.3, 7.8, 8.7 [gc]. Messier (probably) mis-identified his own discovery, globular cluster M69, with Lac I.11. However, M69 is probably too faint for Lacaille's modest telescope, off in position, and there are the 3 stars at Lacaille's position.
Lac II.1 (asterism): Twelve stars of mag 7.6 to 9.5 [gc].
Lac II.2 (open cluster?): Eight stars of mag 5.9 to 8.9 [gc]. May be open cluster Collinder 140, which is 2 deg N [rs].
Lac II.6 (open cluster?): Open Cluster Trumpler 10 [gc, confirmed by rs]. This cluster is situated about 12' W and 11' S of Lacaille's position. It is of 15' apparent diameter, total visual mag 4.6, with about 40 stars up to mag 6.42, so clearly within the reach of Lacaille's equipment (even visible to the naked eye under good observing conditions).
Lac II.11 (asterism): Line of 8 stars mag 6.6 to 8.5 [gc].
Lac III.1 (star): Star mag 7.2 [gc], = HD 32806 = SAO 217150 of mag 7.1 [rs].
Lac III.3 (open cluster?): Open Cluster van den Bergh-Hagen (vdB-Ha) 47. This cluster is situated very close to Lacailles position (2' W, 1' S) which is well within the cluster's diameter of 13' [hf, confirmed by gc and rs].
Lac III.9 (asterism): Three stars of mag 8.1, 7.6, 7.9 [gc].
Lac III.14 (asterism): Three stars of mag 8.4, 8.2, 9.1 [gc].

Former attempts by Owen Gingerich (1960) and Kenneth Glyn Jones (1975) of the identification of Lac II.8 (with NGC 3293) failed due to unknown strange reasons, perhaps because Arthur Auwers had once added a question mark to his cautious identification of this object. Vehrenberg has it, though.

Also, Ronald finds from its description and position that Lacaille III.5 is probably open cluster Collinder 228, situated in the southern part of the Eta Carinae Nebula NGC 3372, not a duplication of Lacaille III.6 as is proposed by Gingerich (and consequently, Vehrenberg).

References:

Cozens, Glen, private communications 1998-2000.
Gingerich, Owen, 1960. Abbe Lacaille's List of Clusters and Nebulae. Sky & Telescope 2/1960.
Glyn Jones, Kenneth, 1975. The Search for the Nebulae.
Stoyan, Ronald, 2001. Der Katalog von [The catalog of] Abbé Nicolas-Louis de Lacaille (1713-1762). interstellarum No. 18 (July 2001), p. 46-48. In German.
Vehrenberg, Hans, Atlas of Deep Sky Splendors. Vehrenberg+Sky Publishing. 1st ed 1965, 3rd ed. 1978. Chapter on "La Caille and his catalogue of southern objects."

Hartmut Frommert
Christine Kronberg
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Last Modification: September 18, 2007