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RA: 17h 40m 41.36s
Dec: −53° 40′ 25.3″
Ch: MSA:1495, U2:434, SA:26
Ref: SIMBAD, SEDS
Type: globular cluster
Mag: B=7.39, V=6.68
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This globular cluster was discovered by Lacaille and included in his 1755 catalogue as Class III No. 11. In his half-an-inch 8x telescope he saw it as a "faint star in nebulosity."
James Dunlop observed it from Paramatta, New South Wales, and included it as No. 366 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a pretty large nebula, extended nearly in the parallel of the equator, brightest and broadest in the middle; a group of very small stars in the middle give it the appearance of a nucleus, but they are not connected with the nebula, but are similar to other small stars in this place which are arranged in groups. The nebula is resolvable into stars."
Sir John Herschel observed it at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "globular cluster; fine; large; bright; round; gradually brighter to the middle; not very compressed; 5' diameter, but stragglers extend a great way. In the middle is a more compact group of much smaller stars. The stars at circumference are larger than in the middle; at N.f. border is a double star." On the second occassion, Herschel "viewed past meridian, a fine, large rich cluster; not very compressed, stars of 13th magnitude. In the S.f. part is a delicate double star." His last observation recorded it as a "Beautiful globular cluster; large; rich, somewhat coarse, 10' diam. taking in all outliers; rather irregularly round, very much compressed in the middle where, however, the stars are very small, while every where else they are 13th magnitude."
"!! globular cluster, fairly condensed"
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Described in Union Obs. Circulars, 45-76, p 50. "Nebulae, clusters, etc. on Sydney Plates" as "a fine cluster, 15' in diameter, the very centre is confused and looks nebulous, there are about 150 stars in all."
Burnham notes that it is "not one of the richer globulars, but has a rather loose, scattered structure which permits easy resolution in relatively small telescopes. The extreme diameter is close to 20', and the total magnitude is 7.3. The two dozen brightest stars (10..12th mag) show no evident concentration towards the cluster centre, but seem to be distributed in random groups and curving rows across the background of fainter members. The cluster closely resembles the better-known M4 in Scorpius." Burnham also notes that it is possibly the nearest globular cluster, and and also one of the oldest.
Photo Index by Jim Lucyk: Burnhams V1 p243, Ast.Obj.for South.Tel. (Hartung, 1984), Universe Guide to Stars & Planets (Ridpath & Tirion) p78.
The mean blue magnitude of the 25 brightest stars, excluding the 5 brightest, is 12.71.
The RNGC (Sulentic and Tifft 1973) notes that this is a 7.5 mag globular cluster.
RA 17 40 41.3 (2000) Dec -53 40 25 Integrated V magnitude 5.73 Central surface brightness, V magnitudes per square arcsecond 15.65 Integrated spectral type F4 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 2.50c: Core radius in arcmin .05. ["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) ]
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Harrington, P. (1986) An observer's guide to globular clusters. Sky&Telescope, Aug, 198.
.. reoslution is possible with 6inch and possibly even smaller telescopes.
Hartung writes that "on a clear dark night this cluster makes a wonderful sight, with bright scattered outliers over an area 20' wide round the well-condensed centre 3' across; there are orange stars in it and some of the outliers are in arcs and sprays. This is one of the best globular clusters for small telescopes, 3-inch resolving it well."
Sanford notes that "visually it resembles M4 in Scorpius, with the brightest stars scattered across the 'face' of the grouping, with no concentration in the centre."
Phil Harrington (1990, Touring the Universe through Binoculars) writes that it "presents an attractive face through binoculars. Although no separate stars are visible, a definite 'grainy' surface texture is seen through large glasses, as if stellar resolution were imminent ... due to its far southern declination .. it is destined to remain a little-observes beauty."
ASV Journal Vol 24 No 3 June 1971: "beautiful object - many stars in 6-inch 64x."
In re Dave Knisely's follow-up on M22: its brightest stars are V=10.7, so sure enough you can see them in a pair of 7x50 binoculars, or a 50mm stop on a telescope. If you ever go south, have a look at NGC 6397, whose brightest stars are V=10.0 (the brightest of any globular). Even omega Cen and 47 Tuc stars are 1.5 magnitudes fainter!
"10 Easy Globs!" by Marilyn Head (105 Owen Street, Newton, Wellington, Aotearoa / New Zealand; email@example.com)
NGC 6397 lies about halfway between and down from Alpha and Beta Arae. Because it is close (7200 l.y.), the stars are mostly resolveable and cover a wide field in a regular, circular pattern , which makes it exceptionally pretty.
naked eye - vis w/o difficulty. BS, 8Nov1993, LCO.
15cm - nice br gc w/rel open struc @ 50x. 80x: wk even concen in halo to circ
core lacking much concen. halo 25' diam, reaches as far as matched
pair SSE of center, but not as far as br * NE. 50x shows fuzz at
threshhold---the horiz branch. 140x: core 1/10 total diam, has cen pip
10" across that is clump of *s elong N-S. one fairly br * E side of
core. well res. BS, 8Nov1993, LCO.
Location: Night Sky Caravan Farm, Bonnievale.
Date: 2016 Oct 30, Sunday.
Time: 22:55 SAST
Telescope: Little Martin (4-inch f/6.5 Celestron refractor)
11-mm Nagler Type6 (60x): Quite large, very obvious globular cluster, not much brighter to the middle. Many stars resolved across its broad centre. 11-mm shows it well.
As seen in 8x40 binoculars, the cluster lies near two bright stars, forming a right-angled triangle with them. When near the horizon, it looks like an unfocused star and can be passed over without recognition, but is nevertheless reasonably easy to spot.
A 15.5-inch reflector resolves the edge of the cluster into stars, but the centre is not resolved, appearing angular. The cluster is small but pleasant to view, and it appears rather untidy, with many stars around it which straggle from the cluster outward.
1997 Sept 03: 11x80 tripod-mounted. 23:00 SAST. Jonkershoek. Very bright broad-centered globular. Several field stars very close by. Rating: very easy. Easy to find, since it shares the picturesque field with the blue-white Gamma Ara and the orange Beta.
1998-04-23/24, 11x80 tripod-mounted binoculars, Die Boord. Seeing good, transparency below average, dew. "pB, L, R globular, with three small stars in the outer reaches. Forms a 90° triangle with two bright stars (one is Pi Ara; cluster at hypotenuse). The cluster grows gradually brighter to the middle, to a broad dense bright disc, 6' across. With averted vision, the cluster expands to delicately cover a 14' circle of sky."
Location: Pietersburg South 23o 53. East 29o 28.
Sky conditions: Clear.
Date: 4 Julie 1997.
Field of view: 52.7 arc minutes.
ASSA-DSO - Report J
NGC 6397 mag 5
Bright, round cluster of stars really close to one anther with a very dense gaious core. Outliers are visible.
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
Very large, bright, round globular cluster with a hint of a core. Well-resolved close stars form arms and trails randomly, with dark patches in between. Between 18 and 20 arc minutes.
NGC: 6397 - ARA
RA: 17h40m41s - DEC: -53°40'25" - Magnitude: 5.7 - Size: 25'
Telescope: 12" S/C - 76x - 95x - 218x – Date: 29/06/2008 – Site: Alldays
The core impress me most, it appears as curly up with a small string going SW, to share with brighter stars on the rim. Slightly elongated NW-SE impression. Higher power reveal a smaller unresolved knot towards the middle.
16-inch f/10 SCT (127x, 290x)
Well resolved splash of various magnitude stars, which is very open seen that it is a globular. Just 10' SW of the double star Pol 4. Round in shape with a three dimentional feeling to it.
12-inch f/10 SCT (EP: 2-inch 40mm SW 76x 53' fov; 2-inch 32mm SW 95x 42' fov)
Very large, bright, round globular cluster with a hint of a core. With higher magnification (95x) the core appears compact. Well-resolved stars form arms and trails randomly from the centre, with dark patches in between. Three yellowish tinted, estimated 9th magnitude stars can be seen toward the southern part of the globular in between the star streamers. Star trails intermittently shaped like arms, as well as speckled dark sections in between. Closest cluster of this type to the solar system. An exceptional observation of Bennett 98.
Sky Conditions:The fainter parts of the Milky Way are barely visible.Haziness only visible on the horizon.Atmosphere stable with little interference.
This globular cluster has the shape of a fluffy dog and that the stars in this cluster is very well resolved.In overall the stars in this cluster is strongly concentrated towards each other and that the nucleus of this cluster is strongly concentrated in the center.This globular cluster is well resolved into over 200 stars which range in brightness from 9th to 10th magnitude.This globular cluster measures 6.2'x 4.4'.Chart No.28,NSOG Vol.3.
Instrument:12-inch Dobsonian Reflector Telescope.
Sky Conditions:Whole Milky Way is visible.
Transparency of the Sky:The sky is clean.
Seeing:Atmosphere is stable with little interference.
Limiting Magnitude:Magnitude 6.
Object Type:Globular Cluster.
First Impression:This object looks like a globular cluster.
Chart Number:No.18(Extract taken out of "Atlas of the Night Sky").
Size:26mm Super Wide Field Eyepiece:Field Of View:57'/8=7.1'.
20mm Ultra Wide Angle Eyepiece:Field Of View:50'/7=7.1'.
Size in Arc Minutes(Nucleus):7.1'.
Globular Cluster is 7.1'*2.3'.
Brightness Profile:The central outskirts of this globular cluster grows extremely bright compared to the far outskirts of this globular cluster.
Challenge Rating:Stunning Sight.
The stars in this globular cluster are well resolved into a large agglomeration of bright individual stars.The stars in this globular cluster NGC 6397 are slightly concentrated towards the nucleus. There are plenty of stars radiating slightly away from the far outskirts of this cluster.
Location: Betty's Bay
Telescope:12" Dobsonian - F4.9 Eyepiece 15mm. FOV - 36'
Sky conditions: Seeing 3/5 (gibbous Moon)
Apparent size: 12'x12'
Actual dimensions: 25.7 x 25.7 Cartes du Ciel)
Globular cluster in ARA.
Fuzzy coarse blotch. No bright nucleus. No stars resolved. The visible group of stars seem to be lying in front of the cluster.
A row of three bright stars from E-W connect two strings of fainter stars that form a wide V shape. In the eyepiece the object,together with the stars, looks like a TeleTubby
After reducing( N up E to the left) a row of three bright stars from E-W connect two strings of fainter stars that form a wide V shape.
To the N a small group of stars, 3 of same brightness as the stars in the V-shape and two very faint stars seem to cradle the Globular cluster.
The object is situated in a rich star field.
The Messier objects
The Bennett objects
The Caldwell list
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