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omega Centauri

Lacaille I.5, Dunlop 440, NGC 5139, GCl 24, C 1323-472, HD 116790, Bennett 61, Caldwell 80, omega Centauri, h 3504, GC 3531

RA: 13h 26m 45.89s
Dec: −47° 28′ 36.7″

Con: Centaurus
Ch: MSA:953, U2:403, SA:21

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

(reference key)

Type: globular cluster

Mag: B=?, V=3.9

Size: 55′
PA: ?

Image gallery

Sketches  (1)

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Photos  (21)

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Remarks

It was plotted in the Almagest of Ptolemy over 1800 years ago, and in the early 17th century it was catalogued by Bayer as a star. The first telescopic observer to see it as a cluster was Halley, who observed it from St Helena in 1677.

Historical observations

Lacaille (1755)

It was observed by Lacaille and included in his 1755 catalogue as Class I No. 5, classifying it as a nebula. He wrote: "Naked eye, a 3rd mag star [10 Cen] in a fog. Telescope, [Half-an-inch aperture, 8x magnification] like a big diffuse comet."

Dunlop, James (1827)

James Dunlop observed it from Paramatta, New South Wales, and included it as No. 440 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a beautiful large bright round nebula, about 10' or 12' diameter, easily resolvable to the very centre; it is a beautiful globe of stars very gradually and moderately compressed to the centre; the stars are rather scattered preceding and following, and the greatest condensation is rather north of the centre: the stars are of slightly mixed mags, of a white colour. This is the largest bright nebula in the southern hemisphere." Dunlop observed it 8 times.

John Herschel

Sir John Herschel observed it at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He wrote of it as "the noble globular cluster w Centauri, beyond all comparison the richest and largest object of its kind in the heavens. The stars are literally innumerable, and as their total light when received by the naked eye affects it hardly more than a star of the 5th or 5..4th magnitude, the minuteness of each may be imagined: it must however be recollected that as the total area over which the stars are diffused is very considerably (not less than a quarter of a square degree), the resultant impression on the sensorium is doubtless thereby much enfeebled, and that the same quantity of light concentrated on a single point of the retina would very probably exceed in effect a star of the 3rd magnitude. On a consideration of all the sweeping descriptions, as well as from a great many occasional inspections of this superb object, I incline to attribute the appearance of two sizes of stars of which mention is made to little groups and knots of stars of the smaller size liying so nearly in the same visual line as to run together by the aberrations of the eye and telescope; and not to real inequality. This explanation of an appearance often noticed in the descriptions of such clusters, is corroborated in this instance by the distribution of these appearently larger stars in rings or mesh-like patterns, chiefly about the centre where the stars are most crowded. An attempt has been made to imitate this appearance in the drawing, but partly from the difficulty of its execution, partly from defect of engraving, the plate fails to convey a just idea of it. Two such rings on an oval crossed by a kind of bridge is especially conspicuous in the central part." In the records of his telescopic sweeps he recorded it as "Diameter full 20'. It much more than fills the field. When the centre is on the edge of the field, the outer stars extend fully half a radius beyond the middle of it. The stars are singularly equal, and distributed with the most exact equality, the condensation being that of a sphere equally filled. - Looking attentively, I retract what is said about the equal scattering and equal sizes of the stars. There are two sizes 12th mag and 13th mag, without greater or less, and the larger stars form rings like lace-work on it. One of these rings, 1.5' in diameter, is so marked as to give the appearance of a comparative darkness like a hole in the centre. There must be thousands of stars. To the naked eye it appears as a star of 5th mag or 5..4th mag, rather hazy. There is a 9th mag star on the S.p. border of it, about 4' or 5' south of centre, and several 8th mag are scattered far away. My attendant (J.S.) called up, who saw the hole and darkness, and described it as I have done above. On further attention the hole is double, or an oval space crossed by a bridge of stars. Position of axis = 150 ." His second observation recorded it as "very very bright, very very large, very very gradually much brighter in the middle; all clearly resolved into stars of two mags, viz. 13 and 15; the larger lying in lines and ridges over the smaller. Near the centre are two distinct darkish spaces formed by a deficiency of the larger stars 13 mag within, and an excess without. This most glorious object fills the whole field with its most condensed part, and its stragglers extend three-quarters of a field beyond it either way. It is very conspicuous to the naked eye as a dim cometic looking star, 4th mag or 5th mag."

Swift, Lewis (1896)

"That grandest of all visible clusters, Omega Centauri, given by Bayer, is plainly visible at a good elevation. In comparison with this, 13 Messier in Herculis, is a tame affair. It was also discovered by Halley at St. Helent in 1677, and is one of the six discovered by him. It is visible to the naked eye as a faint circular object. As I see it is about 20' in diamter, and as round as the Sun. In that small space there are many thousand stars from the 13th to the 15th magnitude, suns every one, no doubt doing the same service as our Sun, warming, lighting, guiding and fertilizing a system of planets where people no doubt are dwelling the same as here."

Ref: [1896PA......3..465S] The Lowe Observatory

Published comments

Doig, P. (1925)

Journal BAA, 36(3), Dec, p91

magnificent globular cluster, 31' diam. over denser parts; ... a considerable number of giant stars is visible in this cluster, however, with a moderate aperture.

Shapley, H. & Paraskevopoulos, J.S. (1940)

Galactic and Extragalactic Studies, III. Photographs of thirty southern nebulae and clusters. Proc. N.A.S., 26, 31-36.

Laustsen, S., Madsen, C. & West, R.M. (1987)

Exploring the Southern Sky: A pictorial atlas from the European Southern Observatory. Springer-Verlag.

Scanned image on disk. [1987EtSS.........0L], plate 174.

Melotte, P.J. (1915)

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

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 4.0 mag globular cluster.

Photo index

Photo Index by Jim Lucyk: Sky&Tel. 3/85 p236, Sky&Tel. 3/86 p239, Sky&Tel. 5/72 p325, Sky&Tel. 8/77 p93, Sky&Tel. 9/84 p259, Sky&Tel. 12/80 p477, Astronomy mag. 4/82 p9, Deep Sky #10 Sp85 (back cover), Burnhams V1 p34, Burnhams V1 p563, Ast.Obj.for South.Tel. (Hartung, 1984), Universe Guide to Stars & Planets (Ridpath & Tirion) p106.

Harris, W.E. (1997)

RA 13 26 45.9 (2000) Dec -47 28 37 Integrated V magnitude 3.68 Central surface brightness, V magnitudes per square arcsecond 16.77 Integrated spectral type F5 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.24 Core radius in arcmin 2.58. ["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 mean blue magnitude of the 25 brightest stars, excluding the 5 brightest, is 13.01.

FitzGerald, A.P. (1955)

FitzGerald, A.P. () "Note on the globular cluster Omega Centauri", IAJ, Vol 3, 204.

"In an earlier article (IAJ, 3, 114, 1954) reference was made to a photograph of this lcuster, takne by the writer during a visit to the Boyden Station .... Lindsay has pointed out that the presence of a slightl absorbing cloud on one side of the cluster can be detected by the deficiency of stars (IAJ, 2, 144, 146, 1953). So far as the writer is aware, the presence of dark absorbing matter in the region of a globular cluster has not been detected on photographs. Of special inetrest, therefore, are the thin dark 'lanes' which are discernible on the eastern side of the cluster in Plate XVII and the long serpentine 'lane' on the western side running from north-west to south-east. Whatever may be the true nature of these 'lanes' it seems unlikely thta they are an efect of the random distribution of stars. It may be that they are filaments of nebulosity lying between the observer and the cluster."

Bailey, S.I. (1908)

"!!! globular cluster, fairly condensed"

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

Remarks, p.217: "A magnificent globular cluster, not extremely condensed. More than 6000 stars have been counted on a photograph of this cluster, having a moderate exposure. the whole number of stars can be little less than 10,000. Of these, 128 are known to be variable."

astro-l listserv

Date: Thu, 01 Jun 1995 21:19:14 -0500 (EST)

From: "Tony Cecce, Corning, NY"(CECCE_AJ@CORNING.COM)

Subject: Omega Centauri is mine!

To: astro@mindspring.com

I finally did it last week, I got my first view of Omega Centauri. I was on vacation in Louisiana then on to Cocoa Beach and Orlando. Knowing that this globular would be visible in early evening this time of year I brought along my 10x50 binoculars. I went out to find this object while north of New Orleans. It was difficult to find skies down to the horizon, many trees with the only open areas being parking lots (and lots of lights). I finally ended up on an interstate overpass. I wasn't too hopeful since there was plenty of atmosphere (moisture laden), it was less than 15 degrees above the horizon, and the light dome from New Orleans 30 miles south extended well into the region of centaurus. I began scanning with my binoculars when all of a sudden there it was. Wow! Words escape me in being able to describe what this looked like (but you know I'll try). This was a glow almost the size of the full moon. Faint at the edges, but getting very bright at the center. I had the impression it was more extended than I could see in those skies with my binoculars. I also seemed to be on the edge of being able to resolve it. I viewed this every chance I got after that first night. I also swung over to M3 and M13 for a comparison. Those fabulous Messier globulars don't hold a candle to Omega Centauri. At home again last night I pulled out an 8" f4.5 dob with a 32mm eyepiece and M13 looked the same through that as Omega Centauri did through my binoculars. I can't wait for my next trip south to see this again, and I will set aside time to find a local astronomer who is willing to let me view through their scope.

Clear Skies, Tony

Modern observations

Brian Skiff

15cm - mod f mod rich cl. 140x: 10' diam w/60 *s m11+. wk-mod concen. BS,

26Feb1990, LCO.

gc N5139

eye - easily visible. many occasions!

7x35mm - lg vbr oval elong in pa70. extends a little past m9 * on N side, but not as far as sim-br * SW. strong broad concen, just-grainy texture. BS, 28May1995, TSP.

8x40mm - like a star through a small cloud. BS, 14Feb1970, FtL.

6cm - unimpressive although a few *s res. BS, 14Feb1970, FtL.

8cm - lg oval w/broadly brtr center @ 20x. just gran, vfine grained. consp *s on N and W edges, sev others fntr/farther away. BS, 18Apr1983, Anderson Mesa.

15cm - at lox all 23' is resolved. mod powers are best showing the outliers. HM rates it as the best. BS & HM, FtL.

- in dark sky, 65x: vbroadly concen w/o cen pip. core 8' diam, outliers to 35'. uniformly res with much haze in core. three or four *s in *ism 8' NE.

- fine obj, mod well res @ 50x & 80x. broad oval w/outliers to 35'x25'-30'. strong smooth broad concen overall. 165x: core is more nrly circ, 10' diam. wonderful fine-grained texture across 18' fld. two dimmer patches on N side of core are wkly vis. BS, 14May1988, TSP.

- just a start on this amazing object, whose appearance here tremendously exceeds northern views. 60'x50' for the area covered by the obvious outliers. BS, 23Feb1990, LCO.

- 60'x40' elong ESE-WNW, reaching as far N as triangle of m11 *s (center star going E-W is wide pair). fat oval with the definition of strong broad concen. brtr part reaches m9 * N of center. two dimmer spots appear in NE quad of brtst part or `core,' the Nrn of the two patches being dkr; a little line of m12 *s separates them. 50x/80x show tracery of spider-web net of m12 *s covering oval. seemingly behind this is remarkably br and dense mass of vf *s best viewed @ higher powers. BS, 3Mar1990, LCO.

25cm - huge oval almost filling 1-deg fld, 45'x35'. sev br *s encroach on the outliers. 88x shows beautiful resolution w/underlying haze. two dk spots on the SE side. 112x, same view noted.

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

Hartung writes: "... the main region is about 20' across and its myriad stars are broadly compressed towards the centre. It is powdered with faint stars with a three-inch, and with a 4-inch looks like delicate tangled threads of beaded gossamer. Larger apertures show a pronounced lace-like pattern which seems to be made of small crossing curved lines of stars. Dark lanes and streaks are evident with moderate magnification and the star distribution is far from uniform. On a clear dark night it is a most impressive and beautiful sight."

Harrington, Phil

Harrington writes that this "magnificent 3.7 mag globular is visible to the naked eye. And what a marvelous sight it is. A pair of 7-power binoculars begins to reveal the unparalelleled splendor of Omega Centauri. Observers with exceptional eyesight may just perceive some of the globulars estimated one million stars, but 11x80 glasses will reveal scores ... an 8-inch instrument can resolve stars across nearly all of the clusters half degree disk. Through a 25-inch reflector, I once cracked the core of Omega, seeing countless suns pouring across the field!"

Harrington, P. (1986) More globulars for observers. Sky&Telescope, Sep, 310.

".. the view was stunning. Using a 4.25-inch f/4 rich field telescope, I could resovle countless stars across the cluster, which appears as large as the Full Moon. Some of its stars could even be seen in 11x80 binoculars and several were suspected in 7x50s. The cluster is distinctly oval."

Tsang, Simon

Simon Tsang notes that it appears oval with binoculars; a 13-inch reflector at 120x showed "no obvious dark lanes, and the core was partially resolved. In appearance it was comparable to my view of M13 at 350x in a 16-inch telescope in Ottawa but with three to five times the density of stars ... a breathtaking sight."

Gross, Todd (IAAC)

Your skill: Intermediate

Date and UT of observation: 1/1/98 11:00 GMT

Location & latitude: Cancun, Mexico

Site classification: Urban/Suburban

Limiting magnitude (visual): 5.1 zenith (est) 4.0 (est) in vicinity of object

Seeing (1 to 10 - worst-best): 5 (?)

Moon up (phase?): No

Weather: Clear to pt. cloudy

Instrument: 80mm APO refractor f/6 - f/l 480mm

Magnifications: 16x,32x,69x,138x

Personal Rating (for this aperture): B

This HUGE globular cluster is almost comically big. It is easily swept up by just fishing around in approximately the right spot in 8x32 binoculars. Even in poor conditions, with limiting magnitude around 4, I was able to make it out naked eye with averted vision. In the 80mm scope, it is roughly the size of the full moon, and a perfectly symetrical, bright cotton ball, which is partially resolved at 16x, and esp. 32, 48, and 69x. About 4 foreground stars are particularly bright near the edges, however, the cluster itself only breaks up a little, in these conditions and with this aperture, not breaking into diamond - like points throughout like I can get M13 to do in perfect conditions near the zenith at home. Nevertheless, impressive, and best with averted vision.

___________________________

Boston Meteorologist Todd Gross

toddg@weatherman.com

http://www.weatherman.com

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "3.6M; 36' diameter! Humongous Globular Cluster! An incredible sight when resolved from a low latitude observing site; uneven texture across its broad condensation; never seen as more than a large, soft blur from latitude of 35.5' N; culminates at May's end; plan a trip to North Africa, Mexico or the Caribbean at that time, and take me with you."

AJ Crayon

AJ Crayon, using an 8" f/6 Newtonian, notes: "is the most magnificent globular cluster of the heavens and much better known as Omega Centauri. It is visible in 8X50 finder as large round and bright. It is 6m 20', it is well resolved into hundreds of stars. With averted vision and good seeing conditions it is resolved into a MOST glorious object at 100x!

Steve Coe

Steve Coe, in "SACNEWS On-Line for May 1996", observing with a 17.5" f/4.5 Dobsonian, notes: NGC 5139 is Omega Centauri, I saw it as very bright, very, very large, extremely rich and very compressed at 100X. What can be said about the KING of the Globulars? This fantastic object was overwhelming from Australia when I went to visit Jim Barclay while Halley's Comet was at its best in 1986. The globular filled the field at 140X in his 12.5" f/6. There were chains of stars that meandered outward in all directions from a blazing core. A dark area was seen on the south side of the central section. It can be seen from even mediocre skies, but if you need to dial it up then go to 13 26.8 and -47 29.

Steve Coe, using a 17.5" f/4.5, notes: "Very bright, very, very large, extremely rich, very compressed at 100X. What can be said about the KING of the Globulars? This fantistic object was overwhelming from Australia when I went to visit Jim Barclay while Halley's Comet was at its best in 1986. The globular filled the field at 140X in his 12.5" f/6. There were chains of stars that meandered outward in all directions from a blazing core."

Ed Finlay

1992 May 22

Ed Finlay, observing with a Meade 4-inch ED APO refractor from Johannesburg, 1992 May 22, notes "easy to find; quite visible; like a small round fuzzy cloud. At 184x very dim but quite spectacular with individual stars resolved at edges."

Gordon, Dave

1999 February 27

From: daveafna@hotmail.com

Scope: 10" SCT F10

EP: 15mm Plossel

Observation date: 27/2/99 at 22h30 UT

Location: Marloth Park, South Africa

Seeing: Lev II, good transparency

Omega is a sheer powerhouse away from city lights. At 167 times magnification, individual members could be identified deep into the core of the cluster. The cluster displays a distinct oval shape, unlike most clusters which are round in shape. Colour was light dusky, fading to the edges.

The cluster has approximately 1 million members and is 17 000 light years distant.

Can anybody supply any deeper information for my records on Omega Centauri?

Look forward to any replies

Dave Gordon

Rui Henriques

1997 May 02

10x50 tripod-mounted, 1997-05-02: snow white glow, 30' diameter, 10' brighter nucleus. No stars resolved in cluster. Stars in field form a cone pointing to north east - overall appearance of an ice-cream on a cone. (clear skies, no light pollution on horizon, dew on binocs) [Rui Henriques]

Contemporary observations

Auke Slotegraaf

1993 April 30

30/04/93: Observing with a 6-inch f/8.6 Newtonian at 52x: average time for drift of brightest part = 52.4 seconds = 8.9'.

1991

This spectacular cluster is wonderful in a 10-inch f/5. It is quite amazing that such an awesome object can actually exist. At 30x the cluster is grainy, and at 120x the central haze is clearly shown as stars. The nucleus appears to show some detail; the random scattering of the stars appear to form almost a small ring of stars with a dark central spot, but this is merely a trick the eye and mind play with this wonderful image.

1981

A 15.5-inch reflector at 220x shows this glorious object which fills the field of view with stars. The central disk appears more or less even, whilst with averted vision it is clearly mottled. Look for the brighter knots of stars which surround this central core.

1998 February 23

1998-02-23/24, 6-inch f/8.6 Newtonian, Stellenbosch Rifle Range site. 6.0 (naked eye), seeing very good. Take this one in at the end of the session, with Omega high up. Wow! An indescribable sight, but here goes. Fills the K12.5mm (23 arcmin) field. Stars are seen all over, resolved from the fringe right into the core. Behind this vast collection of very small stars lies the bright nebulous glow of the other thousands of unresolved stars. The fringes of the cluster is an area rich in chains and clumps of stars - the detail and structure is awesome. Peering into the eyepiece creates an almost 3D effect, as if floating over this sphere of stars.

1998 April 23

1998-04-23/24, 5-inch Newtonian, Die Boord. (Rui's telescope)

Observing with Luis, who described Omega Cen as having two sections; an oval outer ring, and a round inner portion. In the low-power binocular eyepiece, just to the N-NE outside the dense nucleus proper, in the fringe of halo stars, as a very small knot of stars, brighter than the other fringe stars; this concentrated region sort of gives the cluster an extended appearance.

Luis reports seeing three large extended streamers of stars, (by sketch, 1/3 of nucleus diameter) -- one a broader one out to the south, and two bowed ones (like legs) to the north and north-east. I did not notice these; examined at the same time with the 4-inch Unitron, and confirmed the N-NE knot, but not Luis' streamers.

Magda Streicher

1997 April 05

Location: Campsite (23 16 South 29 26 East)

Sky conditions: 7 magnitude clear.

Instrument: Meade 8" (Super wide angle 18mm eyepiece)

Date: 1997 April 5

Remarkable rich open cluster. Very dense to the middle with rich faint and bright stars almost look three-dimensional. Stars running out in chains and lanes to the outskirts of the field. Very impressive, resembles a pot full of sugar to me.

(no date)

12-inch f/10 SCT (EP: 2-inch 32mm SW 95x 42' fov; 2-inch 14mm UW 218x 23' fov) and 16-inch f/10 SCT (EP: 2-inch 32mm SW 127x 32arcmin; 2-inch 14mm UW 290x 17arcmin; 2-inch 8.8mm 462x 11' fov)

Very impressive, extremely large and overwhelming rich mass of stars (95x). Mixed magnitude diamond stars randomly scattered almost three dimensional to a dense bright core. Stars running out from deep inside the core in chains and lanes explode into the far outskirts of the field. It displays an inner compact area and an outer oval section spraying into far more than what the field of view might be (218x). To the northwest some 2/3 away from the core a dark lane cuts off a piece. Towards the southwest an 8th magnitude star is seen in the field of view. Resembles a pot full of white sugar to a very dear friend of mine. With 16" S/C (290x) two dark oval patches embedded in the busy core is visible that resembles the eyes of an owl. Probably the lesser density of bright stars that leads to the darker areas. The northern part seems more densely compiled. The inner part is extremely dense in contrast to the softer outer ring. Faint stars crowded together in tight little knots to the south. Omega Centauri was plotted in the Almagest of Ptolemy over 1800 years ago and catalogued as a star in the early 17th century by Bayer. It has approximately 1 million members and is 17 000 light years distant. The first telescopic observer identifying it as a cluster was Halley who observed it from St Helena in 1677. Lacaille observed it from Cape Town and included it in his 1755 catalogue as a Class 1 no 5, classifying it as a nebula. With the naked eye it appears as a 3rd magnitude star surrounded by fog, rather resembling a large, diffused comet. (Mag 3.5; size 36.3'; brightest stars = 11.5 mag)

Kerneels Mulder

2009 January 25

Date and Time: 25 January 2009, 01:45
Location: Prince Albert (Western Cape, South Africa).
Instrument: Orion XT10 10" f/4.7 Dobsonian Reflector
Eyepieces: 8mm (150x, 24′ FOV), 10mm (120x, 26′ FOV), 25mm (48x, 1� FOV)
Sky Conditions: Seeing: 6/10. Transparency: Average
Slightly windy

48x: Very large, very bright globular cluster approx 30′ in size. Very spectacular to observe. Very well resolved. Elliptical shape with stars concentrated towards the centre. Stars look like thousands of grains of sand. Averted vision resolves stars in centre better. The core is slightly brighter than the outer region. Brightness gradually fades to edges. Approx 80 stars of varied brightness can easily be counted in the outer region. Thousands of stars are resolved towards the central region which also has a diffuse glow from unresolved stars.

Chris Vermeulen

2006 April 01

2006/4/1, 22h02

Sky Conditions: Low light pollution

Quality of Observation: Good

Discovery, Roodepoort

6" Dobsonian, 25mm & 10mm Eyepieces

Clearly visible with the naked eye, Omega Centauri appears as a very small fuzzy object in the south east, in line with Alpha and Beta Crux at about three times the distance from Beat Crux, as what Alpha and Beta Crux are apart. At 48x magnification it appears like a star with a dense cloud, but at 120x magnification one can distinguish the densely compacted stars in the centre and the more "loosely" grouped stars towards the outer rim of the globular cluster. Omega Centauri is a wonderful object to observe and a very fine globular cluster at that if compared to most other globular clusters.

Carol Botha

2007 February 17

Date: 2007 02 17, 23:55

Location: Betty's Bay

Instrument: 8-inch Dobsonian, 17mm eyepiece

Sky: Misty patches, good skies in open patches

Notes: Large bright globular cluster. Fuzzy ball � denser in the middle. Fuzzy filaments radiating from the nucleus � almost looks like candyfloss. Four bright stars form diamond shape around the cluster. 17mm eyepiece does resolve a few stars.

Gary Lillis

2008 April 14

2008 April 14, 23:10

Walmer, Port Elizabeth

2.5-inch f/7.6 refractor (EP: 25mm 28x 45arcmin fov)

Conditions: No wind, clear.

Size=36arcmin, V=3.7. One of the closest known globular clusters at 17 000 light years. Large, bright and visible with the naked eye. Large concentration toward the nucleus M7 10arcmin, the outer halo slightly dimmer at M7.2 5arcmin. NGC 5139 is totally unresolved and stands out well from the background. Few field stars in the vicinity of 8th-9th magnitude. NGC 5139 is easily found and visible through small binoculars.

Richard Ford

2015, February, 23rd

Location:Perdeberg.

Time:1:15am.

Sky Conditions:The fainter parts of the Milky Way are barely visible.Haziness only visible on the horizon.Atmosphere stable with little interference.

Instrument:12-inch Dobsonian.

NGC 5139 has the appearance of a giant mottled snowball where all the stars in this globular cluster are well resolved that most of the stars in this cluster are very strongly concentrated towards each other.This globular cluster measures 19.5'x 15'.Chart No.81,NSOG Vol.3.

2010 February 14,Sunday

Location:Koornlandskloof.

Instrument:12"Dobsonian Reflector Telescope.

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.

First Impression:Globular Cluster.

Location:Centaurus.

Time:11:21pm.

Chart Number:No.17(Extract taken out of "Atlas of the Night Sky").

Size:26mm Eyepiece:Field Of View:57'/3=19'

20mm Eyepiece:Field Of View:50'/2.5=20'. 19'+20'=39'. 39'/2=19.5'. Size of nucleus vs.halo:3/19.5'=0.1'. 2.5'/19.5=0.1'. 0.1'+0.1'=0.2'. Size of halo:0.2'.

Brightness:Extremely Bright.

Brightness Profile:High Surface Brightness.

Challenge Rating:Very easy object to observe in a very dark sky.

The stars in this globular cluster is well composed of bright individual stars that are well resolved into hundreds and thousands of stars in a large bright halo.The stars in this cluster is strongly concentrated towards each other in a large halo of individual stars that presents a slight bluish tint.There are clump chain of bright stars in the halo of this cluster well arranged in a geometric pattern.Towards the central outskirts of this cluster some prominent empty spaces are noted.

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)

Sky conditions: Good (8.5/10)

Quality of observation: Good

THE most impressive globular cluster of all. Looks like a 3D ball of flickering Xmas lights (white). A few prominent (marker) stars near and in it.

m = 4. Size core 20-arcmin (50-arcmin total cat)

Favourite lists

Lacaille's catalogue

The Messier objects

Dunlop's catalogue

The Bennett objects

The Caldwell list

Named DSOs

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open cluster
globular cluster
planetary nebula
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dark nebula
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asterism & stars
unverified/lost
nova

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