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NGC 6171 (13,790 of 18,816)


oc gc pln bn dn gx gxcl ast aka lost




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Messier 107

NGC 6171, C 1629-129, GCl 44, Bennett 79, Messier 107, VI 40, h 3637, GC 4211

RA: 16h 32m 31.91s
Dec: −13° 03′ 13.1″

Con: Ophiuchus
Ch: MSA:1349, U2:291, SA:15

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

(reference key)

Type: globular cluster

Mag: B=9.96, V=8.85

Size: 13′
PA: ?

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Photos  (1)

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This cluster was observed by both Mechain and Messier.

Historical observations

William Herschel (c.1784)

Synonyms: H VI-040

Recorded on May 12, 1793 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a very beautiful extremely compressed cluster of stars, extremely rich, 5' or 6' in diameter, gradually more compressed towards the centre."

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, very rich, gpmbM, diam in RA = 20 seconds, that of the most compact part 4.5 seconds; stars well separated."

NGC/IC Dreyer (1888, 1895, 1908)

It is described in the NGC as "large, very rich, very much compressed, round, clearly resolved into stars". Its catalogued diameter is 10' and integrated magnitude 8.1.

Published comments

Doig, P. (1925)

Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part II. M.N.R.A.S., 35(8), 280.

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 10.0 mag globular cluster.

Bailey, S.I. (1908)

"cluster, globular? fairly open, somewhat irregular"

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

Harris, W.E. (1997)

RA 16 32 31.9 (2000) Dec -13 03 13 Integrated V magnitude 7.93 Central surface brightness, V magnitudes per square arcsecond 18.84 Integrated spectral type G0 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.51 Core radius in arcmin .54. ["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) ]

Modern observations

Bennett, Jack

Bennett observed it with a 5inch short-focus refractor, including it in his list of cometary objects as number 79.

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

Hartung writes: "Of extended and only broadly condensed type, this globular cluster is about 3' across, resolved into faint stars and irregularly scattered outliers which are just apparent with a 6-inch telescope, while a 4-inch shows only a patch of haze. A 2-inch refractor shows this small cluster lying in the centre of a Southern Cross-like asterism spanning a quarter of a degree. The clsuter is pretty bright, appears even with no concentration although it seems to be condensed more to its North-Western side. With averted vision the cluster appears slightly granular.

Bortle, John (1976)

John Bortle (Webb Society Quarterly Journal, January 1976) using 10x50 binoculars, estimates the visual magnitude as 8.2.

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "9M; 7' diameter; just barely resolved faint stars against unresolved background; rich with compressed center; individual stars 14M and dimmer."

Gramer, Lew (IAAC)

Observer: Lew Gramer; Your skills: Intermediate; Date and UT of Observation: 1997-07-4/5, 03:25 UT; Location: Savoy, MA, USA (42N, elev 700m); Site classification: rural; Limiting magnitude: 7.1 (zenith); Seeing: 4 of 10 - medium good, increasing cumulus; Moon up: no; Instrument: 50mm Simmons binoculars; Magnification: 7x; Filters used: None; Object: M107; Category: Globular cluster; Constellation: Oph; Data: mag 7.8 size 10'; RA/DE: 16h33m -13o03m

Description: M107 was discernible to binocs as a HINT of a round "dot", near the edge of the same binoc field SW of bright whitish zeta Oph. Averted vision was needed, no detail noted.

Callender, John (IAAC)

Observer: John Callender (e-mail: jbc@west.net, web: http://www.west.net/~jbc/); Instrument: 8-inch Dobsonian reflector Location: Carpinteria, CA, USA; Light pollution: light Transparency: good Seeing: excellent; Time: Sat Jul 12 07:20:00 1997 UT Obs. no.: 208

A medium-sized faint patch at 49x, detectable with direct vision, but needing averted vision to see at all well. Finding it with the Tirion Sky Atlas required a tough hop through a fairly star-poor region.

Steve Coe

Coe, using a 13" f/5.6, notes: " Pretty bright, pretty large, compressed, round, resolved at 100X, going to 165X brings out about 20 stars. Sentinel 8/10 Trans, 6/10 seeing: Easy in 11X80. 100X--Bright, large, much compressed, very rich, well resolved and much brighter in the middle. 220X--25* resolved and very rich background, very mottled from un-resolved stars, lots of stars right at limit of a good night."

Johnson, Bill

Bill Johnson of Rialto, California, used an 8-inch Newtonian to observe the cluster, and described it as a "pretty low surface brightness globular" but adds that it still shows some structure." He used high to medium powers to observe it.

Ware, Donald J

Donald J. Ware:"This moderately faint object needed a high power and averted vision to yield resolution. It is about 8' in diameter, and is slightly flattened on its northern edge. The brightest area appears to be in the southwestern corner."

Contemporary observations

Auke Slotegraaf

1993 September 24

24/09/93: 11x80 binoculars, strong moonlight: Appears only as a faint star-like point.

1995 June 01

1995-06-01: 11x80. Kelsey Farm. 23:00 SAST. This gc lies close south of a 7th mag right-angled triangle of stars. It has quite a low surface brightness as it is well spread out and doesnt quite have the magnitude.

1997 July 7

1997 July 7, Monday, 21:00 - 24:00 Jonkershoek. 11x80's tripod-mounted. Conveniently located close south of a right-angled triangle of stars. Moderately bright to faint puff of light about 5' across.

Magda Streicher

(no date)

12-inch f/10 SCT (EP: 2-inch 32mm SW 95x 42' fov; 2-inch 14mm UW 218x 23' fov; 2-inch 8.8mm UW 346x 15' fov)

Large, bright globular, reveals faint stars all over this roundish soft globe except for the core which is getting slowly brighter. Appears like a soft unresolved ball of haze. Hazy outliers grow with higher power (218x). Beautiful imbedded in a southern-cross shape of stars with even a pointer appropriate to the northern star-field. (Mag 7.8; size 13.0'; brightest stars = 13 mag. )

Richard Ford

2015 August, 9th


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.

In this globular cluster the stars have a granular appearance looking like an out of focus snowball.Towards the central nucleus of this cluster the stars are slightly loosely concentrated towards each other.This globular cluster to note looks, slightly condensed.This globular cluster measures 5.7'x 4.3'.Chart No.291,NSOG Vol.2.

2009 August 15th Saturday


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.



Chart Number:No.12(Extract taken out of "Atlas of the Night Sky").


Brightness Profile:Medium Surface Brightness.

Challenge Rating:Easy to observe in dark skies under a large telescope.

Overall Shape:This globular cluster is slightly oval as a large mottled snowball of faint stars just resolvable as faint stars.

Are individual stars seen? Yes,some individual faint stars in this cluster are seen.This cluster displays a granular appearance of faint stars not readily seen,but some stars are seen.

How are the stars concentrated towards the nucleus? The stars in this cluster is slightly spherically concentrated and well compact towards the nucleus.

Estimate the size of the nucleus vs.halo: Nucleus(10.1') Halo(8.9').

Are there clumps/chains of stars? Yes,there is a slight concentration of faint stars around the outkirts of this cluster.

Prominent empty spaces/starless patches? No starless patches are discerned.

Tom Bryant

2008-07-03 00:00:00

Observing site: Pinnacles overlook

Telescope: C-8

[16h 32m 30s, -13 3' 0"] ~ 100 stars seen with averted vision. Not bright

2008-06-12 01:30:00

Observing site: Little Tycho Observatory

Telescope: C-8

[16h 32m 30s, -13 3' 0"] AKA M 107. Missed this one. Perhaps a finder chart would show it. The deep sky does not do well in light polluted skies.

2009-04-18 22:30:00

Observing site: Pinnacles overlook

Telescope: C-11

[16h 32m 30s, -13 3' 0"] Faint, looks like its pictures

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