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RA: 05h 35m 12s
Dec: −04° 24′ 0″
Ch: MSA:278, U2:225, SA:11
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 33pn
Mag: B=?, V=4.2
Detection of new nebulae by photography. Annals Harv Coll Obs., 18, 113. Bibcode: [1890AnHar..18..113P]
Photographs taken with the Bache telescope, a photographic 8-inch f/5.5 doublet, covering 10 degrees square, were examined by Mrs M Fleming with a magnifying glass.
"NGC 1981. Coarse cluster, well shown on all the plates."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 25' and the class as 2 3 p.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part III. M.N.R.A.S., 35(9), 316.
"cluster of 8 rather B and many F *."
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.
Table, p.177: "Clusters" noted by Bailey but not included in the Catalogue:
NGC 1981: A few stars north of Great Nebula in Orion. Not considered a cluster.
(Sulentic and Tifft 1973) notes that this is a open cluster.
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "4.6M; 25' diameter; bright, large, scattered group of 20-plus 8 thru 10M members; includes DBL ST Struve-750 (4.3" separation @ PA 060; 6-8M)."
05 35.2 -04 26
8: bright cluster with about two dozen stars mag 6 and fainter. Very large, scattered. Includes ...750 = 6.0-8.0 at 40". To the S is another group of bright stars surrounded by the emission nebula N1973-N1977.
Observer: Lew Gramer; Your skills: Intermediate (some years); Date/time of observation: 1998-02-19/20 03:30 UT; Location of site: Medford, MA, USA (Lat 42oN, Elev 5m); Site classification: Suburban; Sky darkness: 5.6 Limiting magnitude; Seeing: 7 1-10 Seeing Scale (10 best); Moon presence: None - moon not in sky; Instrument: 7x50 handheld binoculars; Magnification: 7x; Filter(s): None; Object(s): NGC 1981; Category: Open cluster; Class: III 2 p n/III 3 p; Constellation: Ori; Data: mag 25' size 4.6; Position: RA 05:35 DEC -04:25;
Description: Next up on my whirlwind binocular tour of Astronomical League list objects tonight (see previous logs for Hyades, n1647, n1746) would be a prominently placed cluster which I had somehow failed to note in my log all these years! n1981 is maybe the easiest AL Binocular Deep-Sky object to find, for anyone with ANY interest in deep-sky. For it lies just one degree N of the Great Orion Nebula (M42) and actually forms the fourth or "grip" "star" in Orion's sword! This night, 1981 revealed no less than 10 stars to direct vision in the 7x50s, but beneath them essentially NO haze of unresolved fainter stars... This was unusual, but no amount of averted vision or hand steadying would turn up any hint of haze underneath - although per- haps 1-2 more individual stars could be seen intermittently. But, the bright stars formed into two interesting groups: one a crooked N-S line of three mag 7 stars, and the other a "hook" of somewhat fainter stars sweeping from this line out to the W and then S. All in all, a MAGNIFICENT field showing M42, M43, iota & 42 Ori as well!
Steve Coe, using a 13" f/5.6, notes: "Bright, large, scattered cluster of 28 stars at 100X. Double star Struve 750 on the NE side. Just north of the Orion Nebula."
Alldays (22.50S, 20.12E, 770m).
12-inch f/10 SCT (95x, 218x)
Very loose large grouping of relatively bright stars. This cluster can be seen with the naked eye using averted vision? just to the north of the "Great Orion Nebula". Only a handful of bright stars with faint ones standing out.
Karoo Star Party, Britstown, Northern Cape, ZA.
15x70 Celestron binoculars
How nice of Charles Messier to put his signature on his most famous deep sky discovery.
Use binoculars, a finder scope or a RFT to see this florid "M", �� wide, due north of M42. It is, of course, the brightest stars of NGC 1981, the cluster that marks the hilt of Orion's Sword. Northern hemisphere star gazers may see it as a "W" instead, but to my mind, the cursive M is obvious.
Observing site: Little Tycho Observatory
[5h 35m 12s, -4� 26' 0"] A field filling cluster of around 10 bright, blue white stars. Just North of M 42. Superb, but dwarfed by M 42 itself.
Sky Conditions:The fainter parts of the Milky Way are barely visible.Haziness only visible on the horizon.Atmosphere stable with little interference.
This open cluster is not separated.In this cluster I have counted over 40 stars which has an irregular appearance of loose bright 7th to 9th magnitude stars.I have also noticed that the stars in this cluster are nearly the same brightness as each other.In overall I have found that the three stars lie in an East-West direction from the other 6 stars in this cluster.The cluster measures 19.5'*6.5'.From the bright stars in this cluster they are comparatively brighter than the stars on the outskirts of this cluster.Challenge Rating:Very Easy.Chart:No.267,NSOG Vol.1.
Location: Bonnievale SSP (Night Sky Caravan Park)
Telescope: Skywatcher 200-mm f/5, Delos 8-mm (0.57-deg fov)
Binoculars: Canon 12x36 IS (5-deg fov)
Sky conditions: Good (8/10)
Quality of observation: Good
NGC 1981 Open cluster, 8 prominent stars (binocs). m = 4; size about 40-arcmin (28-arcmin cat.)
The Messier objects
The Bennett objects
The Caldwell list
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