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NGC 2447 (4,829 of 18,816)


oc gc pln bn dn gx gxcl ast aka lost




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Butterfly Cluster

NGC 2447, Cl Melotte 76, Cl Collinder 160, Cl Raab 63, C 0742-237, COCD 163, Messier 93, Butterfly Cluster, h 3098, GC 1571

RA: 07h 44m 30s
Dec: −23° 51′ 12″

Con: Puppis
Ch: MSA:343, U2:320, SA:19

Ref: SIMBAD, DAML02, Archinal&Hynes (2003)

(reference key)

Type: open cluster, 13r

Mag: B=6.57, V=6.2

Size: 10′
PA: ?

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Sketches  (1)

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Historical observations

Messier, Charles

This bright open cluster in the Puppis Milky Way was discovered by Messier in March 1781. He described it as "a cluster of small stars without nebulosity... between Canis Major and the prow of Navis" Messier gave the apparent size as 8'.

William Herschel (c.1784)

In the Appendix to the 1912 'Scientific Papers of Sir William Herschel' this object is described as "1784, November 20. A cluster of scattered stars, pretty close and nearly of a size, the densest part of it about 15' diameter, but the rest very extensive."

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 "A fine cluster, scarcely scattered, pretty rich, not much more compressed in the middle. Nearly fills field. Stars 8..13th mag."

Webb, T.W. (1893)

Webb calls it "a bright cluster in a rich neighborhood" and Admiral Smythe wrote of it as "a neat group of a star fish shape... S.p. portion being brightest, with individuals of 7-12 mag... Mistaken for a comet by Chevalier d'Angos of the Grand Master's Observatory in Malta"

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 I. M.N.R.A.S., 35(5), 159.

Raab, S. (1922)

Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.

Discussed, based of F-A plates.

Bailey, S.I. (1908)

"cluster, fairly condensed."

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

Melotte, P.J. (1915)

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

Trumpler, R.J. (1928)

Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 18' and the class as 1 3 r.

Burnham's Celestial Handbook

Burnham describes the cluster as "smaller but brighter than M46; the central mass being distinctly triangular or wedgeshaped with outer branches and scattered sprays of stars to a diameter of about 24'" Burnham mentiones that K G Jones, writing in "Messier's Nebulae and Star Clusters", perceives the over-all appearance of the cluster as a butterfly with open wings. Hartung speaks of M93 as a beautiful cluster which merges into a rich starfield, containing "many small pairs, triplets and elegant groups, including two orange stars Sp"

Doig, P. (1926)

"A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.

"well defined, strongly condensed, irreg, rich region." He gives the approx. diameter as 29 arcmin.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 6.5 mag open cluster.

Modern observations

Walter Scott Houston

Houston notes that the cluster is visible to the naked eye under excellent sky conditions. He writes: "my 4-inch refractor showed M93 as 14' in diameter, but a 10-inch reflector made it up to 24' across."

Steve Coe

Steve Coe, observing with a 13" f/5.6, notes: "Bright, large, rich, somewhat compressed, 59 stars of mags 9 to 13 counted at 100X. This cluster is triangularly shaped. An unusual feature of M-93 is that there are few stars in the middle, this "black hole" effect can be seen in all the observations I have ever made of this cluster."

Tom Lorenzin

Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6.2M; 20' diameter; appears knotty with many vari-colored stars; 50-plus 8 thru 13M members; 1.5 degrees NW of 3.5M multiple Xi PUP."

Ware, Donald J

Another fine open cluster. It is about 20' in diameter with a distinct triangular or wedge shape. Composed of about 50 stars, it is fairly well concentrated, with a moderate range in magnitudes of the stars."

Callender, John

Observer: John Callender

Instrument: 50-mm binoculars Location: Carpinteria, CA, USA

Light pollution: light Transparency: good Seeing: fair

Time: Wed Feb 5 05:25:00 1997 UT Obs. no.: 56

A small, easy, comet-like glow in 7x50s. Elongated E-W; almost apeared to have a fan shape, with the bright point of the fan pointing W.

Contemporary observations

Auke Slotegraaf


A 10-inch f/5 at 30x shows that this very interesting cluster's brightest members are a very wide pair on the southwestern edge; this double also points southwest. The brightest cluster members form an isoceles triangle on the western edge of the cluster, while the eastern part has less stars. Overall, the stars are irregularly distributed, being more dense on the one side; the stars seem to lie in three arch-shaped gatherings.

1998 January 03

1998 January 3/4; Jonkershoek. 11x80 tripod-mounted; seeing good; some scintillation; lim mag about 10.7 at pole; daytime view reasonably crisp. "An open cluster, in a rich field, in two parts. The first is a triangular, capital-A shaped compact grouping, 8 arcmin long oriented SE-NW. This A-shape is brightish stars is rather lop-sided in shape, like the Star Trek com-badge/logo. Averted vision clearly shows the second, much larger, component of the cluster extending generally east and north of the A-section. This part is a discrete, delicate scattering of small stars, growing to cover an area 20 arcmin across.

The western extent of the cluster is difficult to pin down since it simply fades away into the extremel rich background. The eastern and southern boundaries, however, are more clearly delineated, by what appears to be dark nebulae. Several dark areas in the field, especially in a line to the south of the cluster.

2007 April 15

Sutherland (Ouberg Quarry)

11x80 tripod mounted binoculars

Conditions: NELM: fainter than 6.0 at the S.pole

Bright, moderately large cluster, brightest stars form a triangular wedge oriented NE-SW, labelled 'A' in the working diagram. This is surrounded by a large halo ('B', 'C') of very very faint stars scattered about, but most prominently to the east and south-east ('B'). Surrounding binocular field wonderfully rich, and textured with dark nebulae. Used Uranometria chart 320 to locate it.

Gerrit Penning

2004 May 29

Date observed: 29/05/2004

Location: Boyden Observatory, Bloemfontein

Limiting Magnitude: 5

Transparency: Clean & Clear

Light Pollution: 60% moon

Instrument: 8-inch refractor, 30 mm, 25' fov

General impression of object: A great looking dense open cluster with stars of similar brightness and size, filling the major part of the view. Scattered stars to edges. Easy to find with binoculars.

A large telescope magnification will not justify the splendour and true size of the cluster.

Rating: 8/10

General impression of its surrounding area: [Binocular]: The cluster is situated in a star rich area of the sky and in milky way, giving impressive views when scanning the area with binoculars.

Description of object:

[Telescope]: This beautiful open cluster filled almost the entire field of the eyepiece. A slight consentration of stars were seen to the south west of the field, 2 brigthter close lying stars marking the south western upper region. Other small "patterns" could be seen (with specific attention to a little "diamond" shape of stars to the centre). Faint stars are scattered all over, with relatively equal brightness. The cluster does not lend itself to a specific shape - strings of stars pile over its "edges" in most directions.


The moon had no material effect on the telescope observation, due to open cluster's brightness. Good detail could be seen, but object not too easy to draw. Fatigue in arm did set in after a while!

Gary Lillis

2008 February 28

2008 February 28, 21:30 SAST

Walmer, Port Elizabeth

2.5-inch f/7.6 refractor (EP: 12.5mm 56x 30arcmin fov)

Conditions: Stable, becoming unstable later.

Size=22arcmin, V=6.2. Mainly a faint cluster, constitutes primarily of coarse stars 10.1-10.5 with a few brighter M9.4-M9.5 stars scattered throughout the cluster. Averted vision reveals stars a little clearer, brighter chain of stars M9.4 stretches northeast to southwest, with a small concentration of stars toward the centre. NGC 2447 is a very dense cluster, with a glow of unresolved stars. Eight stars are within the range of the telescope. Cluster is well attached to field stars of similar magnitude. M9.6-M9.8 scattered throughout the 45arcmin field of view, with two noticeable stars: 45arcmin south M6.8, and 36arcmin southeast M7.5. NGC 2447 was a challenging object to locate. (Second report) V=6.2, size=22arcmin. Challenging to find, mainly a very faint cluster, constitutes primarily of coarse stars M9.6 to M9.9. Slightly brighter stars M8.8-9.2 scattered throughout the cluster. NGC 2447 appears very dense, with an underlying glow of unresolved stars fainter than mag 9.6. Averted vision reveals visible stars a little more clearer. A brighter chain of stars M8.8 runs northeast-southwest, with a small concentration of coarse stars towards the centre of the cluster. NGC 2422 is well-attached to field stars of similar magnitude M9l.6-M9.8 scattered in most directions; southeast 36arcmin M7.5 and south 45arcmin M6.8 are two brighter stars apart of the starfield.

Richard Ford

2009 January 25, 22:15 SAST


12-inch f5 (EP: 26mm SW, 20mm UW, 7mm UW)

Conditions: The most clear sky possible. Dark moon and stars magnitude 6 and fainter are visible with the naked eye. Excellent clean sky, limited star flickering and brilliant objects. Limiting Magnitude: 6.2.

Open Cluster located in Puppis. Extremely Bright. Irregular and slightly compact with bright companions close to the centre. It has many stars grouped towards the outskirts of this cluster. The cluster is not separated but slightly compact. Over 30 stars within a fixed diameter. Most of the stars in this cluster are within 1st and 2nd magnitude. The stars basically are nearly the same brightness as each other. They are strongly concentrated slightly towards each other. In this cluster there are some starless patches towards the central outskirts. Towards the centre chains of stars are slightly concentrated. No obvious prominent stars, coloured stars, or striking double stars seen.

Tom Bryant

2010 11 5 4:38:11

Observing site: Fall Star Party

Telescope: C-11

[7h 44m 36s, -23 52' 0"] A very large, rich open cluster, it fills the field of the 30mm.

Favourite lists

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