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RA: 10h 21m 24s
Dec: −51° 44′ 0″
Ch: MSA:978, U2:426, SA:20
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 23p
Mag: B=6.15, V=6
This cluster was discovered by Lacaille and included in his 1755 catalogue as Class II No. 7. In his half-an-inch 8x telescope he saw it as a "group of four or five faint and very close stars."
James Dunlop observed this object from Paramatta, New South Wales, and included it as No. 386 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "11 Roboris Caroli. A group of 8 or 10 pretty bright small stars, with very small stars, about 6' diameter."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "a group of 9 large, and a few scattered small stars."
Hogg, A. R. (1963) "The Galactic Cluster NGC 3228" MNRAS, 125, 4, 307-312.
"Colours and magniutdes (UBV) are given for 26 stars in the galactic cluster NGC 3228. The observations, combined with available astrometric data point to seven stars as certain members but 11 others lie close to the main sequence. The colours in the region range from B-V = -0.1 to B-V = +2.0 but there is doubt whether stars redder than B-V = +1.0 are actual members. The cluster lies at about 500 parsecs on the inner edge of the Carina-Cygnus arm."
An image, taken at the Newtonian focus of the 74-inch, is reproduced. In the catalogue, the V magnitudes range from 6.94 to 14.53.
"Cat. of Open Cl. south of -45° Decl.", Mem. 17 Mnt Stromlo Obs.
A loose cluster of brihgter stars on a faint field.
The RNGC (Sulentic and Tifft 1973) notes that this is a 6.5 mag open cluster.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 20' and the class as 1 2 p.
brtst in center V=7.90/-0.03.
15cm - lg sparse grp of 25 * m8-11.5 in 15' area centered on grp of six. no
concen of f fld *s, so evidently no others besides these. good for 50x/
1.2deg fld. BS, 23Feb1990, LCO.
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.
Obvious small bright knot of stars, compact. Near the centre is a bright, near equilateral triangle of stars (another slightly fainter star also). 11x12.5mm can barely see the individual stars as resolved.
1998-03-20/21, 11x80 tripod-mounted binoculars, Stellenbosch Rifle Range site; seeing good. A tight approx. 5 arcmin knot. Surrounded by a variety of large and small stars, out to whereever you like. Thus, no boundary. Let's say the cluster is 10 arcmin large? The knot of stars are mainly in an east-pointing V configuration. Magnification too low for certainty, *guess* there are 10 stars here. Averted vision shows a few; but cannot be held in order to count each one distinctly.
1997 April 14, 02:00 - 04:00 Jonkershoek. 11x80's tripod-mounted. Bright knot of stars, prominent even within its rich field. There are three just about equally bright stars making an equilateral triangle. With averted vision, a few more stars sparkle out. Quite surprised that Lacaille saw "four or five"
1994-02-12 23:00 Die Boord, 11x80s tripod-mounted. A very nice tight knot of three bright stars, neatly resolved. Averted vision shows what could be the glow of others. It appears considerably smaller than the extent indictaed on the Uranometria chart.
1994-01-19: 11x80's, The Boord, 02:00 SAST A bright, small compact knot of stars, visible even while sweeping, with a rich star-field of bright stars to the East.
16-inch f/10 SCT (102x, 290x)
This is the little flower cluster. Consist of 9 stars which is well outstanding against the star field. The middle star of the group is the white 7.8-magnitude HD 89915. Daisy with the stem towards the north and round flower consist of a round ring of stars to the south.
The Messier objects
The Bennett objects
The Caldwell list
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