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NGC 6227 (14,009 of 18,816)

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NGC 6227

NGC 6227, h 3651, GC 4243

RA: 16h 51m 33s
Dec: −41° 13′ 0″

Con: Scorpius
Ch: MSA:1460, U2:407, SA:22

Ref: NGC/IC, Corwin (2004)

(reference key)

Type: star cloud

Mag: B=?, V=?

Size: ?
PA: ?

History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

NGC 6227 is described by JH as "A star 5m in a great cluster, or an immensely rich milky way patch." The star is SAO 227313, and it is superposed on a rich part of the Milky Way, just as JH saw it. There is a good scattering of stars between 5th and 10th magnitude within a degree or two following JH's star -- they stand out well on the Southern Sky Survey film. There are two major clumps of stars here: the southern one surrounds NGC 6231, while the northern clump is Collinder 316; Trumpler 24 is apparently a concentration in the northeastern part of Cr 316. IC 4628, a diffuse nebula, is on to the northeast of Tr 24. This whole region may be JH's "great cluster." The area to the west of SAO 227313 is heavily populated with stars of the 9th and 10th magnitude, but does not stand out as much as the areas to the east.

Following JH, I've adopted the position of the SAO star.

Brent Archinal alerted me to the information about the clusters in the area. Here is his note:

I think there are two possibilities for this object. For one, I looked at a DSS image here (via Skyview) and there's nothing really obvious. However, with histogram equalization of a 30' and also a 90' field, there is a brightening of the Milky Way around the star of about 15-18' in diameter. I think it's most reasonable to assume that this is what JH saw.

On the other hand, could it be that JH was refering to the _really big_ 3 degree grouping of stars here, including Cr 316, Tr 24, NGC 6231, and Zeta-1 and -2 Sco? On a particularly transparent night a few years ago (from here in Virginia), I saw this area well for the first time as it crossed the meridian. This is a very spectacular binocular grouping of objects. Offhand, I would think that if he was refering to such a large grouping he'd describe it better or say something clearer about the size, so I think this is an unlikely identification -- but perhaps still possible.

One identification I would reject is that this is one of the individual clusters, such as NGC 6231, Tr 24, or Cr 316. The 5th magnitude star in question is on the edge of Cr 316, but this group doesn't stand out well at all, at least in the 90' field. Tr 24 is too far to the NE (part of Cr 316 probably), and NGC 6321 is quite obvious to the SE and doesn't fit the description at all.

None of this information corresponds with the observation by Hirsch reported in the Monograph, but he may have just been looking at a scattered group of stars here, if not Cr 316 or Tr 24. The comment by Harrington is probably copied from Hirsch (a number of Harrington's descriptions are similar to Webb Society descriptions, but without credit), and the information from Burnham, SkyAtlas 2000.0, and Houston does not seem useful.

Anyway, since JH doesn't describe any resolved stars here other than the 5th magnitude one, and doesn't make any remarks that would indicate the whole 3 degree wide grouping here, the Milky Way brightening seems the best candidate for this object. It would be nice to have some visual confirmation of this particular area to help confirm this, though.

Observers, to your eyepieces!

Historical observations

John Herschel (1847) Cape Observations

Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "a star 5th mag in a great cluster or an immensely rich milky way patch."

Published comments

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a nonexistent object. Their coded description reads NOCL S.

Modern observations

Steve Coe

Steve Coe, observing with a 17.5" f/4.5 at 100X, notes: "Faint, small, pretty compressed at 135X. This object is given as a rich Milky Way field and there are several clumps in the Milky Way at the correct position so I just chose the most prominent candidate.

Contemporary observations

Magda Streicher

(no date)

16-inch f/10 SCT (127x, 290x)

The bright 5.2Magnitude white star is surrounded by numerous fainter. It gives the impression of a bright lit-up street lamp. The fainter stars looks like a beam of light scattered away from the main star to the NNW for almost 5' in this directions. There is also another string which, is about 20' to the south in a compact string with the star HD 151740 in the middle.

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