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RA: 21h 40m 22.03s
Dec: −23° 10′ 44.6″
Ch: MSA:1381, U2:346, SA:23
Ref: SIMBAD, SEDS
Type: globular cluster
Mag: B=?, V=7.7
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In the Philosophical Transactions, 1814, William Herschel described it as "a brilliant cluster, the stars of which are gradually more compressed in the middle. It is insulated, that is, none of the stars in the neighbourhood are likely to be connected with it. Its diameter is from 2' 40 to 3' 30 arcseconds. Its figure is irregularly round. The stars about the centre are so much compressed as to appear to run together. Towards the north, are two rows of bright stars 4 or 5 in a line. In this accumulation of stars, we plainly see the exertion of a central clustering power, which may reside in a central mass, or, what is more probable, in the compound energy of the stars about the centre. The lines of the bright stars, although by a drawing made at the time of observations, one of them seems to pass though the cluster, are probably not connected with it." In the Philosophical Transactions, 1818, William Herschel wrote: "1794, 7 feet finder, it is but just visible. 1794, 7 feet telescope. it seems to be resolvable, but is too faint to bear a high power. 1810, 10 feet telescope. with 71 power, it appears like a pretty large cometic nebula, very gradually much brighter in the middle. 1783, it appears like a pretty large cometic nebula, very gradually much brighter in the middle. 1783, with 250 power it is resolved into very small stars. 1783, small 20 feet Newtonian, 12 inch diameter, power 200, it consists of very small stars; with two rows of stars 4 or 5 in a line. 1783, large 29 feet Newtonian, power 120, by a drawing of the cluster, the rows of stars probably do not belong to the cluster. 1784, 1785, 1786, 20 feet telescope, power 157. A brilliant cluster. 1810, large 10 feet telescope, with 171 and 220 the diameter is 3' 5 seconds; it is not round."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "globular, B, lE, bM, 4' long, 3' broad; all resolved into stars 16m, besides a few 12m. Two lines of rather larger stars run out N.f."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "moderately bright; beautifully contrasted with an 8th mag star beside it; comet-like with 64x; with higher powers resolvable.
'What an immensity of space is indicated! Can such an arrangement be intended, as a bungling spouter of the hour insists, for a mere appendage to the speck of a world on which we dwell, to soften the darkness of its petty midnight? This is impeaching the intelligence of Infinite Wisdom and Power, in adapting such grand means to so disproportionate an end. No imagination can fill up the picture, of which the visual organs afford the dim outline; and he who confidently probes the Eternal Design cannot be many removes from lunacy.'
Admiral Smythe called it a "fine, pale white cluster .. bright and from the straggling streams of stars on its north edge has an elliptical aspect with a central blaze; few other stars in the field."
An observer using the 72-inch f/8.8 speculum telescope at Birr Castle noted: "spiral arrangement of branches. It lies closely preceding a little north from 41 Cap, a 5th mag star."
This globular cluster is Capricorn was discovered by Messier in August 1764. His small Gregorian reflector with an equivalent modern aperture of 2-inches could not resolve it into stars, showing him only a round nebula without stars: "nebula ... seen with difficulty in an ordinary telescope of 3.5 feet .. it is round and I saw no star there, having observed it with a good Gregorian telescope of 104x."
Hinks, A. R. (1911) On the galactic distribution of gaseous nebulae and of star clusters. MNRAS, 71(8), 693-701.
List 6: "NGC numbers of clusters classed as globular, not in Bailey's catalogue"
Bailey, S.I. A catalogue of bright clusters and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part I. M.N.R.A.S., 35(5), 159.
Galactic and Extragalactic Studies, III. Photographs of thirty southern nebulae and clusters. Proc. N.A.S., 26, 31-36.
Burnham writes: "The central nucleus .. is fairly dense, about 1.5' in size." The NGC records it as "bright, large, slightly elongated, gradually pretty much birghter in the middle, stars of magnitude 12 to 16."
RA 21 40 22.0 (2000) Dec -23 10 45 Integrated V magnitude 7.19 Central surface brightness, V magnitudes per square arcsecond 15.28 Integrated spectral type F3- Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 2.50c: Core radius in arcmin .06. ["Catalog Of Parameters For Milky Way Globular Clusters", compiled by William E. Harris, McMaster University. (Revised: May 15, 1997; from http://www.physics.mcmaster.ca/Globular.html; Harris, W.E. 1996, AJ, 112, 1487) ]
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.5 mag globular cluster.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
"! globular cluster, fairly condensed, unsymmetrical"
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Remarks, p.218: "this globular cluster contains 3 known variable stars."
Hartung notes that it "lies in a fine contrasting field. The well-resolved centre is compressed and two short straight rays of stars emerge N.p. while from the north edge irregular streams of stars come out almost spirally. With outliers the cluster is nearly 4' across. Resolution is just apparent with a 3-inch and clear with a 4-inch."
The catalogued size is 11', but Walter Scott Houston found the stars concentrated into a core about 2' across, "which is surrounded by a halo perhaps twice as large." It is about 8th magnitude and a bit over 10' in diameter. Its bright centre and easily resolved edges make it an interesting object for small telescopes. The cluster makes a long isoceles triangle to the southeast with 34 & 36 Capricorni.
William P. Clarke (San Diego, California, USA) writes in the The Webb Society Nebulae and Clusters Section Report No. 10, July 1992: "Large, bright and well-resolved. Irregular outline with 3 chains of stars extending NW, N and NE. (21-inch f/20, x140)."
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8M; 6' diameter; small and soft-edged with much brighter middle and 12M stellar core; little larger and brighter than N7006; not quite round with brighter stars concentrated in NW quadrant; 10M star 8' to W; two stellar strings extend 1' from core-one radial due N; the other, tangent to outer edge, heads N and a little W; bright star 20' E and a little S is 5.5M 41 CAP."
:"The only object of note in this constellation, this globular cluster is about 8-10' in diameter, and is fairly well concentrated to the center."
1991 15cm obs: m12 * S V=11.43/0.91, 4'.7 radius. m13.5 * S V=13.32/0.94,
6cm - 3'.5 diam, well and sharply [strong sharp?] concen. just E of m9 *. CBL, Roof.
8cm - easy @ 20x. mod concen. br * on W. BS, 15Sep1982, Anderson Mesa.
15cm - 3'-4' diam w/broad center, evenly concen. no res, but edges dented w/dk spaces like deep grooves in circular form. almost as br as M75. BS,
- arms (as per 1982 25cm obs) not consp, but one or two *s in each are vis. BS, 14Oct1982, Anderson Mesa.
- br sharply concen cl partially res @ 80x. m9 * W well outside cl. 195x: outliers reach nrly to m12 * S that is Smost of triangle. another m13.5 * btwn it and center (3/4 way to brtr *) is good edge radius. three strings of *s out N side of core, which is 2'.5 across, versus ~7' for halo. brtst is string of three m13 *s extending out in pa350. mod sharp concen to br hisfcbr core and sub*ar nuc. seems to have many consp giants, then vfew fntr *s. * images show clear diffrac pattern @ 195x despite low Dec. BS, 8Sep1991, Anderson Mesa.
- fairly br cl part res @ 80x. outliers reach 60% way to m8 * W. strings NNW & NW are res here. string on W isn't radial, but starts nr SW side of core and goes NW, tangent to core due W. 195x: strong-eve to mod- sharp concen to vsm 10" clumpy nuc. wk Moonlight. BS, 17Nov1993, LCO.
20cm - 4' diam w/broad core and halo. partially res @ 250x w/pair of *-chains extending out from core on S & W sides. HM/JM/BS, 26Jun1971, FtL.
25cm - well res @ 245x, elong E-W. *-chains extending N, NW, and f one E. 4' diam. nice. FtL.
- a little brtr/lgr than M72, 3'.5 diam, more concen and better res @ 190x. two consp strings of *s: one from center N incl four *s (from innermost, V=13.2,12.1,12.1,13.2); other extending from W edge of core containing three more widely spaced *s (from W side to NW, V=12.4,12.6,12.6). BS, 14Oct1982, Anderson Mesa.
30cm - nice @ 220x. 3'.8 diam w/outliers. core 1' across, rel sm. pretty well res w/gran in core. core abruptly brtr. w 7' is m7.5 *. on N is radial string of three m8.5-9 *s in pa0. also skew string of *s NE (NW?). CBL.
Coe, using a 13" f/5.6, notes: "M30 Bright, large, much brighter in the middle. I counted 45 stars at 220X. This nice globular is easy in the 11X80 finder. It is elongated 2x1 E-W and there are several nice chains of stars on the south side. There are many faint stars that form a backround glow. Sentinel 13" 7/10--easy in 11X80, 100X--bright, pretty large, resolved, elongated 2X1 in PA 90, bright middle. 330X--22 stars resolved, much brighter middle, several chains of stars curve out from core, mostly on north side."
Location: Campsite (South 23 16 East 29 26).
Sky conditions: Clear, steadiness good.
Instrument: Meade 8 inch, Super wide-angle, 18mm eyepiece; 36.2' fov
DSO Report N
Pretty large, irregular bright globular with a well compressed core gradually becomes brighter. Pinpoint startrails in the fringes, and a nice asterim circle of faint stars to the north and a star to the west. About 9 arc minutes in size.
Location: Campsite (23 16 South - 29 26 East).
Telescope: Meade 8" 18mm eyepiece, 36 arcmin f.o.v.
Date: August 1998.
Sky conditions: Not very good.
Description: This globular cluster (resembles a sort of elongated honeycomb covered in bees. Busy globular, well resolved more so to the north and slowly growing brighter to a strong bright core. Smaller than M92, about 6 arc minutes in size, with the beautiful 41 Capricorni to the west just outside this globular cluster.
16-inch f/10 SCT (EP: 2-inch 32mm SW 127x 32' fov; 2-inch 14mm UW 290x 17' fov)
This globular cluster resembles a honeycomb covered with bees. Well resolved more so to the north and slowly growing brighter to a strong small bright core. Stars on the edges curls out in strings into the star-field with a nice asterism circle of faint stars curling out north. Stars appear to flash out significantly to the north. Just set off to the west, 4' arc minutes away the nice bright 8th magnitude 41 Capricorni can be seen in the busy star-field.
1997 October 28, Tue/Wed: Jonkershoek, seeing 3, transparency 3, sky darkness 4, lim.mag. at south pole 6.0 (naked eye), 10.7 (binoculars). 11x80 tripod-mounted. "A pretty small, bright, round glow. Has a small star to the west-southwest of the cluster; this appears brighter than it is shown on the Uranometria chart; more 8th than 9th."
Sky Conditions:The fainter parts of the Milky Way are barely visible.Haziness only visible on the horizon.Atmosphere stable with little interference.
In this globular cluster the stars are partially resolved and that most of the stars in this cluster are moderately condensed.In overall the stars in this globular cluster are strongly concentrated towards each other as a condensed golf ball. This globular cluster measures 4'x 3'.Chart No:331,NSOG Vol.2.
Instrument:12-inch Dobsonian Reflector Telescope.
Sky Conditions:The fainter parts of the Milky Way are barely visible on the horizon.
Transparency of the Sky:Haziness only visible on the horizon.
Seeing:Atmosphere stable with little interference.
Object Type:Globular Cluster.
First Impression:This object looks like a globular cluster.
Chart Number:No.19(Extract taken out of "Atlas of the Night Sky").
Size:26mm Eyepiece:Field Of View:57'/13= 4.3'.
20mm Eyepiece:Field Of View:50'/11.5= 4.3'.
4.3'+ 4.3'= 8.6'.
Size in Arc Minutes:4.3'(Nucleus).
Globular Cluster is 4.3'* 1.4'.
Brightness Profile:The nucleus of this cluster is brighter compared to the far outskirts of this globular.
Challenge Rating:Moderately Easy.
This is a moderately small globular cluster where individual stars are seen and that this cluster is partially resolved.The stars are however concentrated towards like a semi-tight swarm.
The Messier objects
The Bennett objects
The Caldwell list
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