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RA: 06h 41m 0s
Dec: +09° 53′ 0″
Ch: MSA:202, U2:183, SA:12
Ref: SIMBAD, Collinder (1931), DAML02
Type: open cluster
Mag: B=?, V=3.9
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Synonyms: H V-027, H VIII-005
This cluster was recorded by William Herschel as VIII.5 on the night of 18 January, 1784. Using an 18.7-inch f/13 speculum telescope, he called it "double and attended by more than 30 considerably large stars." The associated nebulosity was discovered on December 26, 1785 and recorded as V.27: "some pB stars 7' or 8' S.p. 15th Monocerotis are involved in eF milky nebulosity which loses itself imperceptibly."
(72-inch f/8.8 speculum telescope) "No nebulosity found, and only a few stars arranged in pairs; no cluster. Has there been a change here?"
This object is described in the NGC as "15 Mononceros, cluster, double star, nebulous?" Dreyer comments: "delete the ? An extremely large nebula, about 3 in diameter; the densest part is 12' South-West of 15 Monoceros." The open cluster, also called Collinder 112 and nicknamed the Christmas Tree, spans some 20' and has 40 members, the brightest being of 5th magnitude. The total cluster magnitude is 3.9. The cluster members are mostly young B-type stars, which are imbedded in dense nebulosity which glows from their presence. They form part of the Monoceros OB1 association. At the northern end of the cluster lies the slightly variable blue supergiant S (15) Monocerotis, which has an 8.5 magnitude companion some 3 arcseconds away.
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
"A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.
"cluset round 15 Mon ... with bright and dark nebulosity."
Vorontsov-Velyaminov, B. (1925) "Catalogue of integrated magnitudes of star clusters", Astron. Nach. 226.195. Comparing the brightness of the cluster with the extrafocal images of stars, he estimates the magnitude as 4.71.
(Lick Obs Bul, Vol 14, No. 420) gives the diameter as 30' and the class as 2 3 pN.
Ced 84b (NGC 2264)
Position (1900): RA 6 35.5, Dec + 9 59
Star: cl (Mp=4.4, , SpT=O7s, B)
Spectrum of nebula: emission spectrum (observed)
Classification: Nebulous cluster (milky neb cover the clusters, eg NGC 1976)
Notes: "Ced 84 The nebulous field containing NGC 2264. Ced 84 b = NGC 2264 = GC 1440 = h 401 = H V 27 = H VIII 5. Disc. 1784. FA 123. WP 30. (12, 30, 54, 62, 64, 69, 74, 78, 88 Pl 28, 107, 114, 194, 216, 294, 304, 394, 482, 486, 492, 554, 578, 605, 618, 619, 630 Pl 35, 631, 715, 753, 823). R. The nebulous cluster around 15 (S) Monocerotis = +10 1220 = HD 47839 = Boss 8720. Other HD stars within the boundary of the nebula : +10 1211 = HD 47553. +10 1214 = HD 47662. +9 1331 = HD 47732. +10 1215 = HD 47754. +9 1332 = HD 47755. +9 1334 = HD 47777. +10 1221 = HD 47838. +9 1344 = HD 47887 = Boss 8726. +9 1349 = HD 47934. +9 1350 = HD 47961. +9 1356 = HD 48055."
A catalogue of H-II regions. Astrophys.J.Suppl.Ser., 4, 257-279.
Sh 2-273: "NGC 2264. Appears to be connected with No.275 by lanes of nebulosity."
Lynds, B.T. (1962) Catalogue of dark nebulae. Astrophys.J.Suppl.Ser. 7, 1-52. [also: computer datafile: VII/7A]
The RNGC (Sulentic and Tifft 1973) notes that this is a 4.0 mag cluster associated with nebulosity.
Bernes, C. (1977) A catalogue of bright nebulosities in opaque dust clouds.
IC 446 = Bernes 91
Bernes, in A Catalogue of Bright Nebulosities in Opaque Dust Clouds (Astronomy & Astrophysics Supplement, Vol 29) identified his No. 97 with NGC 2264. He describes an emission nebula, 35' x 20' in extent, appearing very bright on a red POSS plate, and which is part of Sharpless 273.
by Jim Lucyk: Sky&Tel. 2/85 p180, Sky&Tel. 2/87 p227, Sky&Tel. 12/81 p554, Astronomy mag. 2/85 p67, Astronomy mag. 11/85 p97, Vehrenberg's Atlas of Galactic Neb-1 p103, 104, Burnhams V2 p1207, 1208, 1211, 1213.
, in "SACNEWS On-line for March 1997", observing with a 10-inch f/4.5 scope, notes: "NGC 2264 (06 41.1 +09 53) This is an open cluster contained in a very large field of nebulosity, including the cone nebula (which I was unable to observe). I saw the cluster as extremely large, very bright, very poor, not at all condensed. The stars form a rough shape of a Christmas tree with a bright star on the N forming the trunk and a double star on the S forming the top. According to pictures and maps, the cone would point down to the top of the tree. Some nebulosity was seen around the W end near the base, and possibly around the base star. Using the UHC filter did not seem to enhance the nebulosity at all."
described as "30' in size, diffuse nebula and open cluster, 20 stars counted, loose and poor, stars scattered, one bright blue-white star, nebula difficult to see, try averted. Under better than average sky conditions, may make out faint nebulosity. 8-inch, 48x."
writes: "This beautiful group extends half a degree south from S Mon. It's a narrow triangular outline of bright stars in the unmistakable shape of a fir tree with S Mon at its base. The tree is more brightly outlines in stars that photographs suggest - a grand sight in the 6-inch! This whole region of sky is riddled with churning bright nebulae, but the only hint of them in the 6-inch through my light pollution is a large, very indefinite suggestion of a glow around the tree's northwestern lower bough. Dark nebulae, however, reveal their presence all over the place by the blank areas they create in the otherwise rich background of faint stars. The star at the tip of the tree is a nice, wide double, Struve 954 (7.1 and 9.6 mag, sep 13 arcseconds) Extending south from this pair is the awesome and famous Cone nebula, called 'The Throne of God' in Burnham's Celestial Handbook. But despite the nebula's majestic appearance in photographs, its surface brightness is too low to show visually in any telescope - at least as far as I know."
writes: "NGC 2264 is a bright smattering of 40 stars made visible with only the slightest optical aid. And what a distinctive shape! One glance and you will immediately know why the famed amateur astronomer Leland Copeland nicknamed this group the Christmas Tree cluster. Ten of NGC 2264's brightest stars form the tree's main profile. At the north end, S Mon marks the tree's trunk. The other 9 stars shine like lights on the ends of imaginary branches."
writes: "A fine group of about 30 stars, extending 40' x 20' in a prominent pattern, and at the northern end lies the bright yellow 15 Monocerotis; this star has a companion wide north, and there is a good deal of scattered nebulous haze.
Coe (Glendale, Arizona, USA) observing with a 13.1-inch f/5.6 reflector, writes in The Webb Society Nebulae and Clusters Section Report No. 11, January 1993: "A naked-eye spot marks the location of this large, bright, but not compressed cluster. It includes the variable S Mon, and binoculars or a finder telescope will show the Christmas Tree shape of the cluster with ease. Faint nebulosity is brightest near S Mon and on the north side of the cluster. With the 38mm Erfle and UHC filter, the nebulosity extends for two degrees around the cluster. At x100+UHC, dark lane seen in nebula. There are a few very faint stars in this region, a measre of the amount of dark nebulosity that permeates this entire region."
Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "3.4M; features the "CONE" nebula at the tree's S-pointing apex; a rather large cluster, approximately 1 degree in extent; includes variable DBL ST S MON; N2261 (Hubble's Variable Nebula) is 1 degree to SSW."
Just to the south of the second brightest star in the cluster lies the Cone Nebula, which Sanford calls "a wonderful mass of dark material which juts upwards towards the star ... all of this object is invisible in small telescopes, although some people have seen the Cone with a 16-inch f/5.5 and a nebular filter."
Coe, observing with a 13" f/5.6, notes: "is a brighter naked eye spot in the Milky Way that marks the location of this large, bright and not compressed star cluster. Because of the shape of the brighter stars, this is called the Xmas tree cluster and includes the variable S Mon within the tree shape. Binoculars or finder will show the tree outline with ease. The cluster is involved in a faint nebulosity that is brightest near S Mon and on the north side of the cluster. With the 38mm Erfle and the UHC filter the nebula extends for 2 degrees around the star cluster. At 100X with the UHC a dark lane can be seen in the nebula, this is the Cone Nebula. There are very few faint stars in this region a measure of the amount of dark nebulosity that permeates this entire region."
Observing site: Little Tycho Observatory
[6h 41m 6s, 9° 53m 0s] A lovely group of sparklers. The Xmas tree cluster, and looks it.
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.
The stars in this open cluster are well arranged in the shape of a Christmas Tree.However this open clusters stars is not separated and most of the stars are nearly the same brightness as each other.By making use of both the OIII Filter and Ultra High Contrast Filter I have found areas of nebulosity around the bright central star in this cluster.The OIII Filter also brings the fine detail of this emission nebula known as the Cone Nebula.The central stars in this cluster grows brighter compared to the stars towards the far outskirts of this cluster.It measures 19.5'*4.8'.Challenge Rating:Moderately Easy.
Observer: Carol Botha
Location: Betty’s Bay
Instrument: 12'' Dobsonian-4,9. Binoculars 10x50. Eyepiece: 25mm plossl (fov 50')
Sky: Clear. Some light pollution E horison
Limiting mag: 5.55 HD59256
Quality: Very windy. Observing with shade netting shelter
Dimension: 20.0' x 20.0' (Cartes du Ciel)
Open Cluster in Monoceros.
Binoculars: At first I thought the Unicorn’s Horn (asterism) that popped into my eyepiece was supposed to represent the Xmas tree cluster. I actually proceeded to sketch and rename the six stars! Surely this Eiffel Tower could not be the famous Xmas Tree Cluster. Back on that highway between Betelgeuse and Procyon and about a third down the line towards Procyon and slightly N, I find the real xmas tree
25mm: Two bright stars stand out. One (S Monocerotis) at the base N of the tree and one at the Apex S. SW from the center of fov two parallel strings of stars, each containing one bright star light up the tree. Around the bright star at the base (N) of the ‘tree’ is a cluster of faint stars. The bright star at the apex (S) is flanked by two stars of lesser magnitude.
An astro pic by Dieter Willasch in Pearls of the Southern Night Sky comes to mind, where a cluster of stars is dominated by the Cone Nebula. No such luck for me on this night where nebulae seem to have been blown away by the wind.
S Monocerotis, also known as 15 Monocerotis, is a massive variable star system located at the base of the xmas tree cluster (Wikipedia)
The Messier objects
The Bennett objects
The Caldwell list
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