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NGC 6723 (15,492 of 18,816)

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NGC 6723

NGC 6723, Dunlop 573, Cl Melotte 217, GCl 106, C 1856-367, Bennett 119, h 3770, GC 4450

RA: 18h 59m 33.14s
Dec: −36° 37′ 53.3″

Con: Sagittarius
Ch: MSA:1434, U2:378, SA:22

Ref: SIMBAD, SEDS

(reference key)

Type: globular cluster

Mag: B=8.69, V=7.92

Size: 13′
PA: ?

Remarks

This globular cluster lies in Sagittarius near the border with Corona Australis. It is visible in the same field and to the northwest of the reflection nebulae NGC 6726-7.

Historical observations

Dunlop, James (1827)

James Dunlop discovered this object from Paramatta, New South Wales, and included it as No. 573 in his catalogue of 1827. Using a 9-inch f/12 telescope, he recorded it on 6 occassions, describing it as "a beautiful bright round nebula, about 3.5' diameter, moderately and gradually condensed to the centre. This is resolvable. The moderate condensation, and the bluish colour of the stars which compose it, give it a very soft and plesant appearance. This is rather difficult to resolve, although the condensation is not very great."

John Herschel (1847) Cape Observations

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, L, R or vlE, vgbM, diam 5', perfectly resolved into stars 14..16m, with stragglers extending to 8' diam."

Published comments

Helwan Obs. Bulletin No 9 (1912)

"! This region was photographed before I t was discovered that it had already been photographed at Harvard and Johannesburg, but the plates obtained with the reflector and the 4-inch Cooke lens are valuable as confirming the results obtained here. They bear out the description given by Innes in TOC 5, except that there is no dark space south of R Coronae Austrinae (NGC 6729). There are as many as twenty reseau squares (each 5'x5') in which not a single star appears on a two hours' exposure with the reflector. These dark spaces are especially noteworthy as the region cannot be said to be in the Milky Way, being 19 degrees from the galactic plane and well away from the visible star clouds."

Harris, W.E. (1997)

RA 18 59 33.2 (2000) Dec -36 37 54 Integrated V magnitude 7.01 Central surface brightness, V magnitudes per square arcsecond 17.92 Integrated spectral type F9 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.05 Core radius in arcmin .94. ["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) ]

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 7.5 mag globular 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.218: "contains 16 known variable stars"

Photo index

Photo Index by Jim Lucyk: Sky&Tel. 9/83 p277, Ast.Obj.for South.Tel. (Hartung, 1984).

Melotte, P.J. (1915)

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

Modern observations

Walter Scott Houston

Houston notes: "It is just nborth of the curve of stars marking the Southern Crown and in the same low-power field as 5th mag Epsilon CrA. Recently, I looked at NGC 6723with my 4-inch refractor and estimated its total magnitude at 7 and diameter as 5.5'.

Cozens, Glen

Glen Cozens calls it an "impressive cluster .. though difficult to resolve, is beautifully round and bright."

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6M; 7' diameter; barely resolved in deep S sky; requires low horizon and excellent seeing; bright and large; looks a little irregular; 30' to ESE is DIF NEB complex N6726-7-9."

Steve Coe

Steve Coe, observing with a 13" f/5.6, notes: "Bright, large, round, much brighter in the middle, about 30 stars resolved at the edges at 135X. There are several long chains of stars that wind their way out from the edges. This very nice southern globular was easy to spot in the 10X50 binoculars."

Clarke, W.P. (1992)

William P. Clarke (San Diego, California, USA) writes in the The Webb Society Nebulae and Clusters Section Report No. 10, July 1992: "In same low power field as the nebulae NGC 6726-7-9. This globular cluster is large and well-resolved but only slightly brighter towards the centre. (21-inch f/20, x140)."

William P. Clarke (1992, Webb Society Quarterly Journal, 89, 1-7, 'A Visual Survey of the Complex Field Around R CrA & TY CrA') writes that NGC 6723 "is a large object, with a diameter of about 11' and appears to be of roughly inform surface brightness and density except for the fading at the outer edge. Stars around the edge are resolved even at x48 using the 25-cm telescope, and resolves very well at x140 in the 53-cm. A slight elongation N.p.-S.f. is noticeable."

Contemporary observations

Auke Slotegraaf

2016 October 30, Sunday

Location: Night Sky Caravan Farm, Bonnievale.

Date: 2016 Oct 30, Sunday.

Time: 22:19 SAST

Telescope: Little Martin (4-inch f/6.5 Celestron refractor)

45mm Celestron Plossl (15x): Very bright stars share this wide field of view with this obvious globular cluster. A small star lies just outside the fringe of the cluster, which is smallish and has a broad centre with no tight nucleus.

1997 July 09

1997 July 9, Wednesday, 20:00 - 22:00 Jonkershoek. 11x80's tripod-mounted. Moderate conditions. Strange - no Messier number! Brightest globular on this Uranometria chart; about 7th magnitude; moderately concentrated. Close by to 5-6th mag stars.

Magda Streicher

(no date)

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

Large, clear, bright, irregular round globular cluster. Very much brighter to the middle, with stars extended in outliers, and a relative bright star to the south. The cluster resembles a much smaller Omega Centauri. About 7 to 8 arc minutes in size.

(no date)

16-inch f/10 SCT (EP: 2-inch 32mm SW 127x 32' fov; 2-inch 14mm UW 290x 17' fov)

Rightfully beautiful. It is outstandingly bright and exhibited stars of different magnitude that is well distributed across the whole surface, almost three dimensional into the inside of the compact core. Very outstanding and delicate. The northern periphery is richly packed with stars. Star strings on the west appear like straw trails, that gives it a somewhat oval appearance. This globular resembles a much smaller family member of Omega Centauri. Exceptionally white 8th magnitude star situated 10' arc minutes to the south. James Dunlop discovered this object in 1826 from Walles. He describes it as a beautiful bright round nebula.

Richard Ford

2015 August, 9th

Location:Perdeberg.

Time:9:20pm.

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.

This globular cluster has the shape of almost looking like an slightly irregular soccer ball and that the stars in this cluster have a granular appearance.In overall most of the stars in this cluster is strongly condensed and that the nucleus is brighter compared to the outskirts of this globular cluster.This globular cluster measures 7.1'x 5.4'.Chart No.327,NSOG Vol.2.

2015 August, 9th

Location:Perdeberg.

Time:9:20pm.

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.

This globular cluster has the shape of almost looking like an slightly irregular soccer ball and that the stars in this cluster have a granular appearance.In overall most of the stars in this cluster is strongly condensed and that the nucleus is brighter compared to the outskirts of this globular cluster.This globular cluster measures 7.1'x 5.4'.Chart No.327,NSOG Vol.2.

2009 July,18 Saturday

Location:Perdeberg.

Instrument:12"Dobsonian Reflector Telescope.

Sky Conditions:The fainter parts of the Milky Way are barely visible.

Transparency of the Sky:Haziness only visible on the horizon.

Seeing:Atmosphere stable with little interference.

Limiting Magnitude:4.9.

First Impression:Globular Cluster.

Location:Corona Australis.

Time:20:00pm.

Chart Number:No.19(Extract taken out of "Atlas of the Night Sky").

Brightness:Very Bright.

Brightness Profile:Medium Surface Brightness.

Challenge Rating:Easy to observe in dark skies in a large aperture telecope.

Overall Shape:Oval,appears as a large mottled snowball of bright stars radiating slightly away from the center of the cluster.

Are individual stars seen? Yes,towards the central core of this cluster faint individual stars are seen.This globular cluster is partially resolved.

How are the stars concentrated towards the nucleus? The stars are centrally concentrated as a mottled snowball towards the nucleus.

Estimate the size of the nucleus vs.halo: Nucleus(9.2') Halo(11.0').

Are there clumps?chains of stars? Yes,the whole globular cluster has bright stars radiating away slightly from each other.

Prominent empty spaces/starless patches? Yes,around the outskirts there are slight starless patches.

Favourite lists

Lacaille's catalogue

The Messier objects

Dunlop's catalogue

The Bennett objects

The Caldwell list

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