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RA: 05h 12m 19.4s
Dec: +16° 40′ 49″
Ch: MSA:183, U2:180, SA:11
Ref: SIMBAD, DAML02, Archinal&Hynes (2003), Skiff20080430
Type: open cluster, 42r
Mag: B=8.44, V=7.7
This open cluster in Taurus, also known as Collinder 60, is described in the NGC as "large, rich cluster, little compressed, consisting of 11-14th magnitude stars". The 60 or so stars lie in an area 15' across, and as a whole the cluster shines at magnitude 7.7. The brightest star is of 9th magnitude. Trumpler described this cluster as not well detached from the background starfield, moderate range in brightness, rich.
Synonyms: H VII-004
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a cluster of pretty large and pretty compressed stars, considerably rich, 20 or 25' diameter, irregularly round."
Observations with the 72-inch f/8.8 speculum telescope at Birr Castle noted "large loose cluster."
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 16' and the class as 3 2 r. He notes: "The cluster Melotte 29 should undoubtdely be indentified with NGC 1817 and not with NGC 1807."
"A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.
"irregular, probably connected with NGC 1807." He gives the approx. diameter as 30 arcmin.
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.0 mag open cluster.
NGC 1807/1817 :"These two open clusters fit in the same field of view in a low power eyepiece, offering a very pleasing deep sky double. 1807 is about 8' in diameter with about 20 stars in a box or X-shape. 1817 is slightly larger, about 10' in diameter, and composed of about 75 relatively faint stars in a compact grouping reminiscent of NGC 7789 in Cassiopeia."
Sagot and Texereau in Revue des Constellations describe it as unexceptional in smaller telescopes, but appearing in large instruments as several 8th or 9th mag stars on a background of more than 100 faint stars. The diameter is 15'.
Listed by the Herschel Club, described as "some 16 stars counted in the loose grouping, scattered quite a bit and poor. 8-inch, 48x."
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "7.7M; 15' diameter; 60-plus 11M and dimmer members; looks star-porr and scattered at first glance; dimmer members evident with persistent scrutiny; OPN CL N1807 (13' diamater; 20-plus 8M and dimmer members) is 20' to WSW."
Houston calls it "one of an interesting pair of bright clusters in the same field of view", the other object being NGC 1807.
05 12.4 +16 41
17.5: large, roundish group of ~100 stars in a 15' diameter. The three
brightest mag 8/9 stars lie on the W side. This trio is part of a 7' arc
of 15 stars elongated N-S sharply defining the preceding side of the group.
The cluster is fairly well detached except at the E side which merges into
the general field density. About 5' NW of the trio described above is a
mag 8.6 star (unequal double) but it appears detached from the main group.
25' SW is the bright, striking group N1807 which has a cruciform outline.
8: about 65 stars in 15'-20' diameter, large, fairly rich, many faint
stars. Includes three brighter stars on the W side including a mag 8.5
star. Forms a poor version of the "Double cluster" with N1807 25' SW.
Location: Paardeberg (ASSA Cape Centre dark sky site) [33:34.4S, 18:51.3E]
Time: 23:00 SAST.
SQM-L: 20.84 (22dC)
Binocs: 15x70 Celestron
NGC 1807 and NGC 1817 - Intruiging! Binoculars show two arcs of 9th mag stars, each 10' long, separated by twice that distance. The arcs are arranged biconvex, and lie more or less along the north-south axis. Between them is a lone faint star (HD 33480, 9.7V).
The easternmost arc, in NGC 1817, is made up of four stars (V=8.6 .. 9.7). Its brightest star (HD 33572, 8.6V) is at the northern tip of the arc. From here, a narrow (30 degrees) fan of very, very faint - actually, unseen - stars spreads out to the south and east, for perhaps 12'.
The westernmost arc, of four stars, has its brightest star (HD 33428, 8.6V) at the southern tip. It is contained in NGC 1807. The remainder of this grouping's stars are just hinted at.
NGC 1817 is far more prominent than NGC 1807.
These two clusters, together, remind me strongly of NGC 5128 (Centaurus A, the Hamburger Galaxy). They present two unequal, elongated, patches of light, with a dark gap between them, in which lies an isolated little star: the Hamburger Galaxy!
To find the pair of clusters, draw a line from Aldebaran (alpha Tau) to El Nath (beta Tau). Midway is iota Tau (4.6V). Sweep orthagonally to the south, slightly more than one binocular field (almost 5.5 degrees), for the duo. They are quite noticeable when sweeping through the region.
In 8x40 binoculars the cluster shows one hazy star, and a two-inch at 20x clearly shows four stars involved in slight nebulosity of unresolved members.
NGC: 1817 - Taurus
RA: 05h12m15.0 - DEC: +16o41'24"
Magnitude: 7.7 – Size: 16'
Tel: 12" S/C – 218x – 346x - Date: 31 Jan 2008 – Site: Alldays - good
My first reaction was a beautiful balloon full of faint specks. Nice, bright and very much outstanding against the background star field. The grouping running out to a northern point. It displays lines with stars running more or less in a NS direction.
Observing site: Little Tycho Observatory
[5h 12m 6s, 16° 42m 0s] Too faint for tonight's moisture laden skies.
The Messier objects
The Bennett objects
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