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Lacaille II.8 (7,053 of 18,816)

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Gem Cluster

Lacaille II.8, NGC 3293, Cl VDBH 98, Cl Melotte 100, Cl Collinder 224, Gum 30, Ocl 816.0, Raab 85, RCW 51, C 1033-579, COCD 253, Gem Cluster, h 3276, GC 2144

RA: 10h 35m 48.8s
Dec: −58° 13′ 0″

Con: Carina
Ch: MSA:992, U2:427, SA:25

Ref: SIMBAD, DAML02, Archinal&Hynes (2003)

(reference key)

Type: open cluster, 13r

Mag: B=4.84, V=4.7

Size: 6′
PA: ?

Image gallery

Sketches  (4)

Select a sketch and click the button to view

Photos  (1)

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Historical observations

John Herschel

Discovered by Sir John Herschel at the Cape of Good Hope with a 5-inch f/17 refractor. He described it as "a fine bright rich not very large cluster. (Equatorial zone review)"

[It is a great pity he did not view the cluster with his 18-inch f/13 speculum telescope, since the cluster is involved with nebulosity, not mentioned in his description with the smaller refractor.]

Published comments

Raab, S. (1922)

Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.

Discussed, based of F-A plates.

Bailey, S.I. (1908)

"! cluster, fairly condensed, Milky Way"

Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.

Remarks, p.217: "The NGC position of this object is in error."

Hoffleit, D. (1953)

1953AnHar.119...37H

A Preliminary Survey of Nebulosities and Associated B-Stars in Carina.

Area "C"

Table II, p43

Notes to the Catalogue, No. 26, p 66.

Hogg, A.R. (1965)

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

Trumpler, R.J. (1928)

Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 8' and the class as 2 3 r.

Burnham's Celestial Handbook

Burnham calls it an "open cluster, bright, rich, 8' diameter, about 50 stars 6..13th mag, with dark nebulosity to the south."

Melotte, P.J. (1915)

A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.

Van den Bergh & Herbst (1975)

In their "Catalogue of Southern Stars Embedded in Nebulosity" (Astronomical Journal, Vol 80, No 3, 1975) van den Bergh and Herbst list two reflection nebulae involved with this cluster. The first, BHe 42A, has the illuminating star embedded within it, the blue surface brightness is moderate, it is very much brighter on red plates where it has a maximum diameter of 4' (on blue plates it is only 1.6' across). The second nebula, BHe 42B, which lies just to the north and west, lies just outside the illuminating star. It's blue surface brightness is moderate, it is distinctly brighter on the blue plates on which is has a maximum diameter of 1.6'.

Gum, C.S. (1955)

Gum, C.S. (1955) A survey of southern HII regions. Mem.RAS, 67. [1955MmRAS..67..155G]

The nebula was also described by Colin S. GumA Survey of Southern H II Regions published in the RAS Memoirs, Vol. LXVII. He describes Gum 30 as "a more or less detached outer condensation of the Carina complex. There is considerably clustering of B stars apparently associated with the nebulosity. The cluster NGC 3293 whose corrected position is 10h 32.0m -57 43' (1900) is situated towards the edge of the nebula and contains [magnitudes in the second column are photographic and the number in the last column is the distance modulus]:

HD 91943 7.1 B0 9.8

HD 91968 6.9 B0

HD 91983 8.9 B

HD 92007 9.1 B

HD 92024 9.1 B

HD 92044 8.5 B0

Nearer the centre of the nebula are:

HD 91824 8.2 Oe5 12.0

HD 91850 9.1 B2

HD 303068 B

The mean of the two widely differing moduli available place the nebula at a distance of 1500 parsec, which is equal to the distance of the Carina complex with which it appears to be associated." Gum gives the maximum diameter of the nebula, which appears roughly circular, as 40'. The intensity, or "visibility in the particular section of the Milky Way in which the object occurs" is rated as "moderately bright" on a scale of vf - f - mb - b - vb. In his scheme of classifying the large-scale structural features of nebulae, the nebula is rated a "II", which corresponds to "irregular in shape with dark matter, but the concentration towards the centre is less marked and the central intensity is much less than Class I."

Rodgers, Campbell & Whiteoak (1960)

Rodgers, Campbell and Whiteoak include it as part of the main Eta Carinae complex, which they label RCW 53. It is a member of the Carina OB1 Association.

Photo index

by Jim Lucyk: Astronomy mag. 10/86 p107, Ast.Obj.for South.Tel. (Hartung, 1984).

Sulentic & Tifft (1973)

(Sulentic and Tifft 1973) notes that this is a 7.5 mag open cluster.

Sher, D. (1965)

Sher, D. () "Structure of the Milky Way in Carina" QJRAS, v 6, p 299-320. "NGC 3293 is a rich and compact cluster of young stars overlain in parts with relatively faint nebulosity. It has occassionally been refered to as the II Carina association. ... [Michael] Feast's estiamte of the distance is in agreement with an earlier result of 2.6 kpc obtained by Miss Hoffleit and based on observations of 5 stars."

Modern observations

Hartung, E.J. (1968) Astron.Obj.South.Tel

Hartung also does not notice nebulosity, noting that "Marked concentric structure is shown by this beautiful open star group which is somewhat angularly round and about 5' across; it is bright with stars of different colours."

Harrington, Phil

Harrington calls it "a tightly packed swarm of 50 stars from 6th to 13th mag. Through binoculars, only the brightest 10 or so suns can be grasped, surrounded by the glow of unresolved starlight. Six-inch telescopes resolve just about all of the cluster members, while a 10-inch might begin to show the faint cloud of nebulosity that engulfs the group. Although vivid in photographs, the nebula requires optimum equipment, skies and eyes to be spotted visually."

Brian Skiff

Turner: * NW: V=6.73/0.07; a * nr center: V=6.52/0.00.

15cm - brilliant condensed cl @ 80x. 140x: 10'-12' diam at most, but most *s concen in 5' area, m7+. brtst * on NW. 120 *s counted. brtr members in well-def area, only f outliers. reflection neb (DS filter gives mild enhancement) stretches from NW edge due W ~15' as far as m7 *. BS, 21Feb1990, LCO.

Contemporary observations

Auke Slotegraaf

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.

Remarkable! Brilliant compact cluster. Small, very very bright but poor cluster. Three stars closeby in a row northeast-southwest. The final star in the row (at the southwest tip) is a deep orange or red. Many more faint stars make up the group, which overall is elongated 1:2 and lying northwest-southeast.

1994 May 25

1994-05-25?, Die Boord, 11x80. Wonderful night - good definition. Four cluster members clearly seen; 3 lie in a SSW-NNE chain running to the middle of the cluster, the fourth on the NW edge of the cluster. The southernmost star of the three-star-chain is definitely deep-orange, possibly also the fourth (northernwestern) star. Very attractive cluster.

1994 February 18

1994-02-18, Die Boord, 6-inch f/8.6 Newtonian. This is a glorious sight at 52x, forming a box-shaped grouping of large and small stars. I again noticed the orange star situated to the side of the cluster.

1992

A 10-inch f/5 at 30x shows this very nice group as being very tight and compact and exceptionally rich. The stars all appear blue-white expect for one on the side of the cluster which by contrast appears orange-red. At 120x this beautiful cluster appears as a small, compact, very rich group of bright stars.

1982

A 2-inch refractor shows it as a very tight concentration of bright stars, several of which sparkle out.

Carol Botha

2012 -03 - 20

Location:Betty's Bay

Time: 23:00

Telescope: 12� Dobsonian � f4,9. Eyepiece 15mm. FOV- 36�

Sky conditions: Seeing 3/5 (dew)

Actual dimensions: 20.8' x 20.8'(Cartes Du Ciel)

Object description:

Open clusterand nebula in Carina

Can be found with the naked eye.In the eyepiece this object looks almost like a globular cluster with all stars resolved. This beautiful compact open cluster is surrounded by nebulosity. The cluster contains mostly bright stars. Central and slightly to the W 3 bright stars of more or less equal mag. The most W of these appears orange (super red giant of 6.5 mag according to Cartes du Ciel) There are more stars in the E half. Towards the W the stars are more sparcely spaced.

Somehow at first glimpse this object reminded me of the �hubbly bubbly� Hookah pipes so popular in SA bars! The strings of stars, the vapour mist and orange fitting at the end of the hose � almost unmistakable! Best most probably to stick to the description of Gem Cluster

2007 March 09

Date: 2007 03 09, 21:15

Location: Bellville

Instrument: 8-inch Dobsonian, 25mm eyepiece

Sky: Clear; light pollution

Notes: Open cluster. Elongated north-south. Looks almost like a hubbly-bubbly pipe! One bright white star near the centre.

Gary Lillis

2008 March 27

2008 March 27, 19:50

Walmer, Port Elizabeth

2.5-inch f/7.6 refractor (EP: 12.5mm 56x 30arcmin fov)

Conditions: Good and clear.

Bright, defined by a small bright concentration. Hard to determine the outlines, many prominent and coarse stars within close proximity. The main portion of the cluster is a well concentrated group M4. Towards the lower half the semi-circular structure consists of eight stars M7 to M9.5, glowing in unresolved stars fainter than mag 9.5. The semi-circular structure runs southeast to northwest for 40arcminutes featuring mag 6.8 to 8.2 stars, sporadically spaced, creating dark gaps. Isolated from the main group 10arcmin west are two prominent stars M5.9-6.0 accompanied by coarse stars M7.0-7.3. NGC 3293 is well attached to field stars. A large group south-southwest five prominent stars M4.2-7.0 engulfed by many coarse stars M7.1-8.4, 53arcminutes northwest is S Carinae M5. NGC 3293 is found in a very rich starfield.

Richard Ford

2011 February 5th, Saturday

Location:Koornlandskloof,Sutherland.

Instrument:12-inch Dobsonian Reflector Telescope.

Eyepieces:26mm Super Wide Field Eyepiece.

20mm Ultra Wide Angle Eyepiece.

Sky Conditions:Dark moon and stars magnitude 6 and fainter are barely visible with the naked eye.

Transparency of the Sky:The most clear sky possible.

Seeing:Excellent clean sky,limited star flickering and brilliant objects.

Limiting Magnitude:6.5.

Object Type:Open Cluster.

First Impression:This object looks like a compact cluster.

Location:Carina.

Time:10:15pm.

Chart Number:No.16(Extract taken out of "Atlas of the Night Sky").

Size:26mm Eyepiece:Field Of View:57'/7=8.1'.

20mm Eyepiece:Field Of View:50'/6=8.3'.

8.1'+8.3'=16.4'.

16.4'/2=8.2'.

Size in Arc Minutes:8.2'.

Ratio:1:2.

Major Axis:8.2'.

8.2'/2=4.1'.

Minor Axis:4.1'.

Open Cluster is 8.2'*4.1'.

Brightness:Magnitude 4.7.

Brightness Profile:All over this cluster the stars are evenly bright.

Challenge Rating:Very easy.

Description

-----------

By observing this open cluster the stars are well detached.I have counted 15 stars in this open cluster.However despite the fact that this cluster is a compact cluster most of the stars are nearly the same brightness as each other.All the stars in this cluster are strongly concentrated towards each other.

Pierre de Villiers

2016 February 05, Friday

Location: Bonnievale SSP (Night Sky Caravan Park)

Telescope: Skywatcher 200-mm f/5, Delos 8-mm (0.57-deg fov)

Binoculars: Canon 12x36 IS (5-deg fov)

Sky conditions: Good (8.5/10)

Quality of observation: Good

Gem open cluster; U or horshoe shape to south-east. Compact, about 6-arcmin. m = 5. A very compact and neat open cluster with a distinctive pattern; 30+ stars of 5th mag, mainly white.

Favourite lists

Lacaille's catalogue

The Messier objects

Dunlop's catalogue

The Bennett objects

The Caldwell list

Named DSOs

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