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Lacaille II.6 (5,645 of 18,816)

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Lacaille II.6

Lacaille II.6, Dunlop 490, Cl Trumpler 10, Cl Collinder 203, C 0846-423, Cl VDBH 53, Ocl 747.0, COCD 210

RA: 08h 47m 45s
Dec: −42° 30′ 0″

Con: Vela
Ch: MSA:945, U2:397, SA:20

Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003), Cozens (2008)

(reference key)

Type: open cluster, 23m

Mag: B=?, V=4.6

Size: 29′
PA: ?

Historical observations

Lacaille (1755)

Lacaille recorded II.6 as a "heap of seven or eight stars, slightly compressed" and noted its position as 08h 46m 41s,–42° 15' 05" (J2000.0).

Dunlop, James (1826)

Dunlop recorded No. 490 of his catalogue as "A very large cluster of pretty bright stars, coarsely scattered, about 1° diameter, following a star 5th magnitude, 396 Agrus (Bode.)" and observed it twice.

Published comments

Trumpler, R. J. (1930)

Preliminary results on the distances, dimensions and space distribution of open star clusters [1930LicOB..14..154T]

Trumpler gives the diameter as 30' and the class as 2 3 p. He notes: "A large coarse cluster of a few bright and medium bright stars, observed by Dunlop (490) and Bailey. Both observations have been erroneously identified with the cluster NGC 2671, a small cluster of faint stars near by; it is probably for this reason that the cluster was omitted from the NGC."

Lynga, Gosta (1960)

"UBV sequences in five southern galactic clusters" [http://adsabs.harvard.edu/abs/1960ArA.....2..379L]

"Summary: Photoelectric sequences in the UBV system are determined for the galactic clusters NGC 2422, IC 2391, IC 2395, Tr 10, and NGC 3114 by means of the Rockefeller reflector of the Boyden Observatory in South Africa."

Lynga, Gosta (1962)

"On some southern galactic clusters" [http://adsabs.harvard.edu/abs/1962ArA.....3...65L]

"Summary: Magnitudes and colours are determined for stars in the galactic clusters IC 2391, IC 2395, NGC 2470 [sic], Tr 10, and NGC 3114. Proper motions are used to determine membership in IC 2391 and Tr 10. The cluster properties are discussed."

Reports on an investigation of five southern galactic clusters (IC 2391, IC 2395, NGC 2670, Tr 10 and NGC 3114) which were "observed photoelectrically and photographically by the author during a stay in 1958 at the Boyden Observatory in South Africa." The 35.5-inch ADH Baker-Schmidt telescope was used, and the observers were Lynga, H. Haffner, and Bester.

Hogg, A. R. (1965)

"Cat. of Open Cl. south of -45° Decl.", Mem. 17 Mnt Stromlo Obs.

Because of its large size and open nature, this cluster is not too well localized on the plate.

Stock, J. (1984)

An article by J. Stock (Rev. Mexicana Astron. Astrof., 9, 127-137 (1984), "Positions, proper motions and magnitudes in the area of the open cluster Tr 10") notes: "Postions for 979 stars in the area of Tr 10 are derived from fifteen plates taken recently with the CIDA refractor. For the determination of proper motions, nine plates of the Cape Astrographic Catalogue are used as first epoch. The results make it appear doubttul that the object is a single cluster."

The author also notes: "Possible members of the open cluster NGC 2671 are present on several of the CIDA plates. Unfortunately, they are beyond the limit of the Cape plates, such that no proper motions can be given for this object."

Modern observations

Brian Skiff

POSS: no f *s.

15cm - unconcen grp of brtr *s; no f members, only those on U2000 (and some sl fntr). not visually interesting. BS, 22Feb1990, LCO.

Contemporary observations

Auke Slotegraaf

1994-02-12

1994-02-12 23:00 Die Boord, 11x80s tripod-mounted. This cluster appears as a loose, poor scattering of stars. The surroundings are very rich in stars, and the cluster looks like a more concentrated area of the field. It is quite recognizable as a loose cluster, even when sweeping over the area. It is an attractive if scattered object.

-------------

1994-03-09

1994-03-09 22:30 Die Boord. Observing with a 6-inch f/8.6 Newtonian at 52x (50' field approx) this cluster is so spread out that it merges with the background stars to form a 50' field full of large and small stars. The field is sprinkled richly, but remains coarse with many large dark areas. The cluster is not at all detached and the extent is difficult to establish as it has no clear border. Amongst the scattered bright stars in the cluster and some fainter ones, especially the two small triangles of 8-9th mag stars on the southern edge.

-------------

1995-05-30

1995-05-30: 11x80.Technopark. 21:30 SAST. Hazy sky. A poor scattered cluster of large and small stars, covers more than the U200 indicates. Quite prominent.

-------------

1996

A 10-inch f/5 at 30x shows this as a large, very coarse, scattered grouping, just under a third of a degree across. The cluster members are very bright (7th mag and fainter) and are well spread out, but it does stand out quite well from the background. Many geometric shapes (equilateral triangles, a nice trapezium) can be seen. The cluster contrasts nicely with the nearby NGC 2671.

-------------

2002 June 20

Searching for Lacaille II.6

2002 June 20, 20:00. 11x80 tripod-mounted. Stellenbosch Rifle Range site. First-quarter moon. Slight easterly breeze. Working on U 397.

(= Tr 10?)

This grouping - shown on U397 at Trumpler 10 - was noticed while sweeping across the area as a "visual hot-spot". From the bright, pale-yellow d Vel, look due east for an oblong sprinkling of stars. The 11x12mm shows four stars with some cloudiness between them. 11x80 shows a crudely rectangular area, five brighter stars and a similar number of much fainter ones.

Lacaille describes II.6 as "seven or eight loosely grouped stars"; perhaps the brighter stars in this group, and a few similar ones immediately east, are his "7 or 8 stars"?

d Vel is CD-42°4569 (BSC5: 3477, V=4.07, B-V=+0.87); Hoffleit & Warren, in "Preliminary Version of the Bright Star Catalogue, 5th Revised Edition" notes "Possibly member open cluster Trumpler 10."

The only star within Tr10 that is included in the Bright Star Catalogue (5th Revised Edition) is CD-41°4516 (BSC5: 3501, V = 6.43).

-------------

2002 July 01

Stellenbosch (Paradyskloof Rifle Range)

11x80 tripod-mounted binoculars (12.5-mm aperture mask)

Conditions: Dark moon. Slight easterly breeze. NELM approx 5.5 at the pole. Dew.

An obvious gathering of stars while sweeping. Roughly seven stars here, moderately bright, coarse and scattered, not well detached and not rich. Lacaille's description: OK

-----------------

2002 June 20

2002 June 20, 20:00 SAST

Stellenbosch (Paradyskloof Rifle Range)

11x80 tripod-mounted binoculars.

Conditions: First-quarter moon. Slight easterly breeze.

Working on Uranometria chart 397. This grouping was noticed while sweeping across the area as a "visual hot-spot". From the bright, pale-yellow d Vel, look due east for an oblong sprinkling of stars. The 11x12mm shows four stars with some cloudiness between them. 11x80 shows a crudely rectangular area, five brighter stars and a similar number of much fainter ones. Lacaille describes II.6 as "seven or eight loosely grouped stars"; perhaps the brighter stars in this group, and a few similar ones immediately east, are his "7 or 8 stars"? d Vel is CD–42°4569 (BSC5: 3477, V=4.07, B-V=+0.87).

2009 February 27/28

Sutherland (Huis Lana)

"Bertha" 12-inch f/4.8 Dobsonian (EP: 32mm, 25mm, 10mm, 6.3mm Plossls, 2x Barlow, 32mm Erfle)

Conditions: Clear, dark.

With the sweeper eyepiece (47x, 60' fov) its hard to know where to look for this cluster. I see a very large area of bright stars, spanning the one-degree field, loosely scattered. Not impressive. Its far more obvious in the 9x50 finder. (MSA 944)

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