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Lacaille I.7 (11,789 of 18,816)

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Lacaille I.7

Lacaille I.7, Dunlop 273, NGC 5281, Cl Collinder 276, C 1343-626, Cl VDBH 152, COCD 336, h 3531, GC 3640

RA: 13h 46m 30s
Dec: −62° 54′ 54″

Con: Centaurus
Ch: MSA:986, U2:451, SA:25

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

(reference key)

Type: open cluster, 13m

Mag: B=6.15, V=5.9

Size: 7′
PA: ?

Image gallery

Sketches  (1)

Select a sketch and click the button to view

Historical observations

Lacaille (1755)

This open cluster was discovered by Lacaille and included in his 1755 catalogue as Class I No. 1. In his half-an-inch 8x telescope he saw it as a "small indistinct spot."

Dunlop, James (1827)

James Dunlop observed it from Paramatta, New South Wales, and included it as No . 273 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a curved line of small stars, aboutr 1.5' long, with a star of the 7th mag in the north extremity; a group of extremely minute stars on the preceding side of the crescent, and a multitude of very minute stars extended preceding and following." Dunlop sketched the cluster and observed it on 7 occasions.

John Herschel

John Herschel at the Cape of Good Hope observed it with an 18-inch f/13 speculum telescope. He recorded it as "Cluster class VII. Small, compact irregularly roundl 1 8th mag star, and 15 or 20 smaller in a knot. No. 1 in Sweep 578 [NGC 5269] is an outlier of it." His second observation was recorded as "A brilliant, compact milky way cluster. Rich, irregular figure, gradually brighter in the middle; 10'; stars 10..12th mag."

Published comments

Hogg, A.R. (1965)

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

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"

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

Melotte, P.J. (1915)

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

Trumpler, R.J. (1928)

Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 4' and the class as 1 3 m.

Burnham's Celestial Handbook

Burnham calls this open cluster bright, small and pretty compressed, 3' diameter, about 20 stars 10..12th mag.

Vogt, N. & Moffat, A.F.J. (1972/3)

Vogt. N. & Moffat, AFJ (1973), "Southern Open Star Clusters III." Astron.Astrophys.Suppl., 10, 135-193. [image, table]

d = 1.30kpc, earliest Sp = B5.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 8.0 mag open cluster.

Modern observations

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

Hartung notes that a "30cm shows it as a beautiful scattered cluster of fairly bright stars merging into a fine field and concentrated at the centre in a pattern of two crossing curved lines of brighter stars, yellow, bluish, white and orange. The central region is about 4' across and 10.5cm shows it well; on a clear dark night this is a most lovely field."

Brian Skiff

M&V III: brtst * V=6.61/0.18.

15cm - fairly br cl w/four br *s inv (brtst m7). 140x: 75 *s in 8' diam, well

concen around the four br ones. a few outliers to S. BS, 24Feb1990, LCO.

Contemporary observations

Auke Slotegraaf

1981

The cluster appears stellar in binoculars, while a two-inch refractor shows it as a small grouping of stars with one bright star and two slightly fainter ones as prominent members.

1994 January 16

1994-01-16: Very nice in 11x80's tripod mounted. Rich field, with handful of brightish stars scattered around. One of these stars, however, just cannot be focused and remains hazy. Averted vision shows, around this star, a soft glow of starlight like a halo.

1998 April 1

1998-04-1/2, 11x80 tripod, Stellenbosch Rifle Range site, polar naked eye lim mag 6.0, darkness average, transparency very good. Initially, a bright (yellow?) star that resists precise focusing, as if its the only star in the field that exhibits astigmatism. Taking a closer look, shows that this bright star has a stellar appendage to the south-southwest, which is actually two close 9th mag stars. A third half-magnitude fainter star can be made out, just west of the bright star, forming an almost equiliateral triangle of faint stars. By estimate, 90 arcsec wide. Look close north for the orange V766.

Interestingly, the first impressions I had on viewing it, had I done so casually, would probably have described it as a bright star surrounded by fuzzyness. But careful study shows that it is _not_ surrounded by light at all, merely to the south and west. See the binoc obs. of 1994-01-16.

Gary Lillis

2008 April 23

2008 April 23, 20:00

Walmer, Port Elizabeth

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

Conditions: Hardly visible cirrus, otherwise stable.

Distinguishable from stars of similar brightness by having a larger haze, a possible result of the conditions, it also possesed much fainter stars revealed with averted vision. The area around NGC 5281 is relatively barren of field stars 21arcmin northeast M7.1 and 27arcmin northeast M6.5. NGC 5281 has the appearance of a brightish star M6.3 with four faint stars M9.3-9.5 running east-west in a slightly semi-circular shape. The one prominent star has a red/orange appearance. At 28x the cluster appears quite bright, but faint stars are difficult to resolve. The four faint stars revealed at 56x are well packed together. NGC 5281 is a small cluster and reasonably hard to find. Size=5arcmin, V=5.9.

Favourite lists

Lacaille's catalogue

The Messier objects

Dunlop's catalogue

The Bennett objects

The Caldwell list

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