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RA: 08h 11m 54s
Dec: −37° 37′ 0″
Ch: MSA:926, U2:362, SA:20
Ref: SIMBAD, Collinder (1931), DAML02
Type: open cluster
Mag: B=6.46, V=6.3
This cluster was discovered by Lacaille and included in his 1755 catalogue as Class II No. 4. With the naked eye, he called it "two confused groups"; in his half-an-inch 8x telescope he saw it as "many close faint stars."
James Dunlop observed this object twice from Paramatta, New South Wales, and included it as No. 563 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a large cluster of stars of mixt magnitude, rather extended figure, not rich in very small stars."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "a cluster 8th class of about 20 bright stars in an oblong, 8' long, 3' broad." On a second occassion he called it "chief triangle of stars 9, 10, 11th mag of an oblong irregular cluster." His third observation was recorded as "a bright group in full part of a bright, not rich, irregular oblong cluster, 6' long, 3 or 4' broad."
"cluster, coarse, irregular."
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Fernie, J.D. (1963) Observations of four southern galactic clusters. Observatory, 83, 33.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Table, p.177: "Clusters" noted by Bailey but not included in the Catalogue:
NGC 2546: Falls in rich region. Not considered a cluster.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 45' and the class as 3 2 p.
(Sulentic and Tifft 1973) notes that this is a 5.0 mag open cluster.
Harrington writes that "rich-field telescopes reveal an isosceles triangle of 7th- and 8th-magnitude stars framing about 20 stars of 9th magnitude and fainter."
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "7M; 25' diameter; large, round and sparse; 50-plus 9M and dimmer members; binocular object."
Steve Coe, observing with a 13" f/5.6, notes: "Very bright, very large, scattered, not rich, not compressed. 62 stars counted at 60X, one is a lovely dark yellow star on the south side of the cluster. This large cluster is easy in the 11X80 finder."
In binoculars the cluster looks like a brighter patch of the Milky Way. An 11x80 shows a large area, about a degree, sprinkled with very many faint small stars, but not too faint to be resolved. It shows as a faint and rich starfield making an irregular form defying classification. About a degree away lie a pair of double stars, one bright and close, the other pair slightly fainter and more distant.
This is a very striking open cluster when viewed with a 10-inch f/5 at 30x. It appears quite suddenly out of the rich milky way background as an approx. one degree patch of even-brighter milky way background. The cluster seems to lie in a rectangular grouping, elongated roughly north-south. It is very large, and the stars are irregularly scattered across a wide field, forming a loose swathe of stars. On the western edge, just to the south of a pretty bright star, is a tight, elongated knot of stars. Looking at the cluster in the field of view, it looks just like a bright milky way starfield, but when you move the 'scope a bit off and compare it with the real background starfield, it is seen as being something more than just a busy field.
2002 June 20, 20:00. 11x80 tripod-mounted. Stellenbosch Rifle Range site. First-quarter moon. Slight easterly breeze. Working on U 362.
Sweeping with binoculars through this area, centred roughly at 08h16, -36°, shows a very busy starfield, about two degrees square, scattered with stars 4th to 7th magnitude. Between two of these field stars (CD-36 4291 and CD-37 4394, Vmag 6.4) lies a large (about 45') subtle glow, peppered with a buckshot of 9-10th magnitude stars (at the limit of the binoculars tonight). This mottled, large starfield is scatted with tiny stars, and although dim, it is nevertheless plainly seen with attention.
In some ways, similar to NGC 2477 (though the latter is utterly starless).
Through the 12mm Lacaille-mask, nothing of this field is seen.
Stellenbosch (Paradyskloof Rifle Range)
11x80 tripod-mounted binoculars (12.5-mm aperture mask)
Conditions: Dark moon. NELM approx 5.0 at the pole. Immensely heavy dew.
Lac II.4. Beautiful large scattering of very small stars set in a rich field of 7 and 8th magnitude stars. The cluster contrasts beautifully with the bright star-sprinkled field. The star-field, generally north and east of the cluster, is a hazy area to the naked eye, covering 2x2 degrees of sky, bound by Dec. –35° and –37°, RA 08:12 and 08:22. I am unsure what the "two neighbouring .. groups of stars" are; one of them certainly is not NGC 2546. However, his telescopic description of NGC 2545 is spot-on.
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 361. Sweeping with binoculars through this area, centred roughly at 08h16, –36°, shows a very busy starfield, about two degrees square, scattered with stars 4th to 7th magnitude. Between two of these field stars (CD-36 4291 and CD-37 4394, Vmag 6.4) lies a large (about 45') subtle glow, peppered with a buckshot of 9-10th magnitude stars (at the limit of the binoculars tonight). This mottled, large starfield is scatted with tiny stars, and although dim, it is nevertheless plainly seen with attention. In some ways, similar to NGC 2477 (though the latter is utterly starless). Through the 12mm Lacaille-mask, nothing of this field is seen.
Sky Conditions:The fainter parts of the Milky Way are barely visible.Haziness only visible on the horizon.Atmosphere stable with little interference.
This open clusters bright stars are well detached and most of the stars are nearly as bright as each other.All the stars in this cluster are not at all concentrated and that this open cluster is an irregular cluster.This open cluster measures 31'*10.3'.The stars in the center of this open cluster grows slightly brighter compared to the stars on the far outskirts of this cluster.
The Messier objects
The Bennett objects
The Caldwell list
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