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RA: 07h 07m 1s
Dec: +27° 15′ 48″
Ch: MSA:131, U2:138, SA:5
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 42m
Mag: B=?, V=8.5
NGC 2331 is a large, scattered cluster of pretty bright stars. There is a concentration of several stars on the southeast edge that attracted JH's attention enough that he took it as the position for the whole object. Thus, the position in the main table is about 8 arcmin northwest of the NGC place, copied directly from GC and JH.
A curious footnote to this object is in the "Other Observers" column in the NGC: "Flamsteed." I do not know yet why Dreyer credited Flamsteed with the discovery -- there is no mention of the object in Kenneth Glyn Jones's fine book, "The Search for the Nebulae." According to Glyn Jones, Flamsteed did find several other objects in the area, including M41 and NGC 2244. But this cluster is missing from his catalogue and atlas.
Synonyms: H VIII-040
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "clustering, large scattered stars, many of equal size."
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.5 mag open cluster.
Steve Coe, observing with a 13" f/5.6, notes: "Pretty bright, large, not compressed, about 25 stars in a 15 arc minute area, includes a small group in a ring shape at 100X."
15cm - wk cl w/rel poor bkgrnd, abs hole? sparse grp of 30 *s m10+ in 25'x15'
area elong N-S. 1' circlet of six *s on SE side adds interest, these
res @ 80x. cl fair but not terribly interesting @ 50x. BS, 4Feb1991,
NGC: 2331 - Gemini
RA: 07h06m59.0 - DEC: +27o15'42"
Magnitude: 8.5 – Size: 18'
Tel: 12" S/C – 218x – Date: 31 Jan 2008 – Site: Alldays - good
If look at the size it is large in size. What is mostly impress me is a small real cool sircle of stars in this cluster which is situated in the northern part. A triangle of stars is seen towards the south with fainter members in between.
Observing site: Little Tycho Observatory
[7h 7m 12s, 27° 21m 0s] A large group of 5 10mv stars, the 11.5mv stars are barely glimpsed in tonight's hazy sky.
Location:Blesfontein Guest Farm,Sutherland.
Sky Conditions:The most crystal 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.
This open cluster looks like the letter of an H and that I have counted 23 stars within a fixed diameter.I have noticed that this cluster consists of 10.6-11.2 magnitude stars.In this open cluster there are bright and faint stars mixed together and that this cluster is not arranged and not at all concentrated.This open cluster measures 23.9'x19.9'.Chart No.213,NSOG Vol.
The Messier objects
The Bennett objects
The Caldwell list
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