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RA: 17h 44m 24s
Dec: −32° 22′ 0″
Ch: MSA:1416, U2:377, SA:22
Ref: SIMBAD, Collinder (1931), DAML02
Type: open cluster
Mag: B=?, V=?
NGC 6416. See NGC 6421.
James Dunlop discovered this object from Paramatta, New South Wales, and included it as No. 612 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a cluster of small stars of mixt magnitudes, about 15' diameter, irregular figure."
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "Cluster class VIII of stars 11m; fills field; not rich; stars in zig-zag lines." On a second occassion he called it "Coarse, rich, vL cluster. More than fills field. Stars 8..12m, one of 8m taken."
The NGC calls it "very large, rich and only slightly compressed."
Bailey, examining a Bruce plate (Harvard Annals, Vol 72, No 2), describes it as "milky way, pretty compressed, diameter 15'."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 22' and the class as 3 2 p.
Burnham calls this cluster a "sprinkling of star-dust" lying some 50' east of M6.
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.5 mag open cluster.
Photo Index by Jim Lucyk: Sky&Tel. 10/74 p226, Vehrenberg's Atlas of DS Splendors (3ed) p183.
Steve Coe, observing with a 17.5" f/4.5 at 100X, notes: "Pretty bright, large, pretty rich, not compressed and elongated at 100X.
Observer: Lew Gramer; Your skills: Intermediate; Date and UT of Observation: 1997-07-4/5, 03:30 UT; Location: Savoy, MA, USA (42N, elev 700m); Site classification: rural; Limiting magnitude: 7.1 (zenith); Seeing: 5 of 10 - mediocre, increasing cumulus; Moon up: no; Instrument: Naked eye, 50mm Simmons binoculars; Magnification: 1x, 7x; Filters used: None; Object: M6, M7, ngc 6416; Category: Open clusters; Constellation: Sco; Data: mags 4.2, 3.3, 5.7 sizes 15', 80', 18'; RA/DE: 17h45m -32o
Description: M6 and M7 travel together just off of the mainstream of the Summer Milky Way, in a fascinating clump of naked-eye haze patches NE of the many tail stars of Sco. M7 even seemed to "glitter" to the naked eye, with the promise of many resolved stars just on the edge of vision. The edges of both M6 and M7 are just visible in the same binocular field, centered just SW of the fainter open cluster n6416. This bino view is one of INCREDIBLE stellar complexity, with the well-resolved NW edges of M7 filling the lower-left (SE) edge, M6 appearing as a sparkling and MUCH smaller irregular blur peaking around the upper-right (NW) edge, and faint n6416 being fully visible as a sparkling hazy patch toward the middle from M6. Scanning up to M6, a yellowish mag 6 star rides its ENE edge. Bringing M7 into full view, the observer is first struck by a dizzying myriad of field and cluster stars, then by the unresolved haze of perhaps hundreds of stars lying beneath these. Soon however, "dark" areas of relatively less concentration become visible in these light clouds, especially to the NW and SE. Last noted: a striking pair of RED mag 7 stars, just S of the blur of 6416.
1997 July 9, Wednesday, 20:00 - 22:00 Jonkershoek. 11x80's tripod-mounted. Moderate conditions. A soft milky way glow, like a slightly more dense starfield. A handful of small stars seen.
The Messier objects
The Bennett objects
The Caldwell list
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