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NGC 6997 (16,479 of 18,816)

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NGC 6997

NGC 6997, Cl Collinder 425, VIII 58, GC 4620

RA: 20h 56m 39.4s
Dec: +44° 37′ 54″

Con: Cygnus
Ch: MSA:1126, U2:85, SA:9

Ref: NGC/IC, Archinal&Hynes (2003)

(reference key)

Type: open cluster, 32mn

Mag: B=?, V=?

Size: 6′
PA: ?

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

NGC 6997 is a real cluster immersed in the "East Coast" part of the North America Nebula. Several of the cluster catalogues have confused it with NGC 6996, but the GC/NGC position, from a single observation by WH, is pretty good. As with NGC 6996, I (1970) and Brent (1993) have further discussions and observations.

Reinmuth and Bigourdan pretty much agree with these assessments of the three clusters (N6989, N6996, and N6997) involved in the North America Nebula. And they wrote their descriptions long before Brent and I did, independently, and from different observing techniques.

Historical observations

William Herschel (c.1784)

Synonyms: H VIII-058

Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a cluster of pL scattered stars, not very rich."

Published comments

Sulentic & Tifft (1973)

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

[amastro] NGC 6997: another Herschel II Mystery

Well, I did get a good night in at a site southwest of Lincoln, Nebr. (Olive Creek State Rec. Area), and picked up about 18 new Herschel II objects (as well as nicely resolving 72 Peg, Brian). However, I did run into a problem with the identity of the "open cluster" NGC 6997. Although Megastar plots it (twice with two different sized circles), it only appears as a somewhat dubious concentration of stars inside the North American Nebula (near where Detroit would be, humm....). However, Uranometria 2000 and the new version of Sky Atlas 2000 do not plot it (the first edition does). In fact, Uranometria's errata says than NGC 6997 is to be deleted. SIMBAD does not have any information on the entry, so I am once again at a loss. Does this stupid cluster exist or not? There are several other areas in the nebula which also might be considered clusters if NGC 6997 is, although the entire area looks like just one big nebulous star cloud.

On another note, I did roughly measure the size of the outer haze surrounding the planetary nebulae NGC 7027. It appears to be very diffuse and roughly circular, with a diameter somewhere between 1 and 1.5 arc minutes. It is barely hinted at with the Deep-Sky filter, but is visible fairly easily in the UHC, although it has the greatest contrast in the OIII filter. Clear skies to you.

--

David Knisely

------------------------------------------------------------------------

Brent Archinal has published the skinny on this object, which although it has a convoluted history, is nevertheless a real (and to me, conspicuous) object. This is a small cluster of mag. 11-ish stars situated on the North America Nebula as Dave K. describes. It is readily spotted in even 60mm aperture, as per the description in L&S (both here and in Kepple & Sanner the object is erroneously designated NGC 6996---see Archinal's "Nonexistent" NGC clusters monograph for the gory details). Almost any photo of the region, even with a 50mm lens, shows the cluster.

Brian

------------------------------------------------------------------------

David, et al:

I happened to have this object on my "to do" list while visiting my Mum-in-law in Connecticut last month. Her location in southern Fairfield County is pretty horrible for deep sky viewing, but I hadn't been out with the telescope in months and I was desperate to look at anything. I had my Celestron "Comet Catcher" with me and, on a night with a spate of great weather, set up in a grove of trees which offered some protection from the glare of the local street lights.

I spent most of the evening doing the summer Messier objects...while working around Cygnus I noticed that, according to the spreadsheet from "Deep Sky 2000" running on the laptop, that I needed only N6997 to complete my Herschel list for Cygnus. Looking at my logbook I noticed that each of the dozen or so times I'd seen N7000 I'd always used the UHC filter to bring out the nebulosity and never really looked for the stars within, though I'd always noted the abundance of stars in the fore/background. This time I knew there was no hope of seeing the nebulosity, so I decided to look for the cluster itself. Using the chart mode of DS2000 I created a chart spanning 5 degrees, then carefully star-hopped from Deneb to the location of the cluster.

Yes, there is a concentration of stars there. In the 15mm Panoptic (33X) it is set in the center of a north-south trending triangle of 8th mag stars. The bright sky background swallowed up a number of the background Milky Way stars, but the cluster was still evident. Adding the 2.5X Barlow (83X) offered the best view. There were perhaps 2 dozen or so stars within the bounds of the FOV, 10th mag and fainter, but with a definite "fall-off" in background stars surrounding it.

I suspect that the small aperture (5.25-in) and bright sky enhanced the view of this object. In viewing with a larger aperture and darker skies, the fainter background stars probably swallow the cluster up. It might be worth trying to look for this cluster when the Moon brightens the background a bit.

Cheers,

Geoff

+===========================================================+

| Geoff Chester grc@usno.navy.mil Public Affairs Office |

| http://www.usno.navy.mil US Naval Observatory |

Modern observations

Brian Skiff

6cm - elliptical hazy patch 15'x10' in pa150, 10 f *s cast over it.

7cm - cl in North America Nebula. rich fld w/br neb @ 20x/3.2-deg fld makes cl not really consp. 30x/2.25-deg fld lots better. resolved at both powers, however. 50x shows two doz *s broadly concen across center. BS, 21Nov1992, Anderson Mesa.

8cm - unres, but just as obvious as gn 7000. BS, 24Jul1982, Anderson Mesa.

15cm - a f grp of m11+ *s. 25 * res w/haze @ 95x. located in NE `U.S.' of North America Neb.

- in North Amer Neb, consp @ 30x in NE part of `U.S.'. 80x: 10' diam with 60 *s in roughly circ area, poorly concen. consp wide pair nr N side, another fntr one on NW. outliers on SW truncated by `eastern seaboard' of neb. BS, 8Aug1988, Anderson Mesa.

25cm - nice, picked out @ 47x standing out mod well from fld. 60 *s counted at 95x in 15' sl oval area.

30cm - 40 *s in 15' area. unconcen, but distinguishable from fld because of uniformity of mags of the *s.

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