I've been working the last day transcribing my observing notes from four nights at Lassen, mostly from Thursday and Fridays at the Bumpass Hell parking lot. This section includes a mixture of clusters including a review of some difficult globulars (IC 1257, NGC 6749, Terzan 7, Terzan 8 and Tontanzintla 2) as well as some brighter globulars and open clusters which I hadn't looked at critically in several years. I've included some of my older notes of these objects for comparison in smaller scopes.
Steve Gottlieb
17.5" (6/30/00): at 280x this small low surface brightness globular appeared very faint, round, ~30" diameter but visible with direct vision. Appears to have an extremely faint knot at the south edge and a slight central brightening.
17.5" (7/27/95): very faint, round patch, ~1' diameter. Appears similar to a 15th magnitude galaxy with no hints of resolution or central concentration. Can hold steadily with averted vision. Located 5.8' W of a mag 11.5 star. Discovered to be a globular in 1996.
13": not found.
Ton 2 = E333-SC16 = Pismis 26
17 36 13 -38 33.2
V = 12.2; Size 3.4
17.5" (6/30/00): located just 6.6' NW of a mag 4.3 star, this challenging GC appeared as only a weak circular enhancement, ~1.5' diameter, in a rich milky way field. Best view at 220x using averted vision keeping the bright star outside the field. A mag 14.5-15 star is superimposed near the center (offset to the west side). The milky way is patchy in the vicinity and the glow is only marginally brighter if at all. The center is possibly slightly brighter but no core was visible and the halo appeared to fade out.
17.5: not found on 6/3/00 from Fiddletown (exact location examined). Located 6.6' NW of a mag 4.3 star in the tail of Scorpius.
N6402 = M14
17 37 36.1 -03 14 45
V = 7.6; Size 11.7
17.5" (7/1/00): this bright, large, fairly symmetric globular appears elongated ~E-W and ~7'x5' in size at 220x. The bright core is relatively large at 4', very lively and granular with a layer of very faint stars. At 280x, ~30 stars are resolved in the small halo and at the edge of the intense core. A rich, even sprinkling of faint stars cover the core. Difficult to count resolved stars as numerous dim stars pop out with averted vision over the bright background haze, but perhaps 60-70 stars in total are resolved.
17.5": bright, large, 25-30 very faint stars are resolved mostly at the edges which have a ragged appearance.
13": fairly large, broad concentration. About a dozen very faint stars are resolved across the disk. The outer halo fades out smoothly.
N6712
18 53 04.3 -08 42 21
V = 8.2; Size 7.2
17.5" (6/30/00): at 220x this is a bright, moderately large cluster, ~6' diameter in a very rich milky way field. Contains a relatively large, intense 3' core with a number of very faint stars peppered over the background glow. A small, partially resolved piece is detached at the SE end. The surrounding halo includes a number of brighter stars, though difficult to untangle from the rich milky way background. Perhaps two dozen stars are resolved at 280x, though difficult to accurately count. The core has irregular appearance with a flattened core caused by a sharp light-cut off on the south side.
17.5" (7/1/89): about two dozen stars resolved over haze. A very rich clump is visible at the W side and a detached clump is at the SE end. The outline is irregular.
13": about 15 stars resolved including several extremely faint stars, very mottled, ragged edges, non-symmetric (flattened on the SE side).
8": grainy, very lively but only a few stars resolved at high power.
N6723 = E396-SC10
18 59 33.1 -36 37 53
V = 7.3; Size 11.0
17.5: (6/30/00): this is a beautiful, symmetric GC at 220x. The halo extends to ~6' and is sharply concentrated with a very bright 3' core. This core is highly resolved into a dense overlay of faint stars with a single brighter star just north of center. The extent of the halo is ill-defined and consists of numerous brighter stragglers (or field stars) mixed with a sprinkling of dim stars. Perhaps 70 stars are resolved in total. In a remarkable region with a complex of unusual reflection nebulae (N6726/27/29).
17.5" (7/29/92): at 220x, bright, fairly large with about 50 stars visible in a 4'-5' diameter. Fairly symmetric appearance with no distinct edge. Beautifully resolved into several dozen stars. A mag 10.5 star is off the NE edge 3' from the core. Mildly concentrated but no distinct nucleus although a star appears embedded at the center of the core. The outer halo is well-resolved and a peppering of stars are resolved over the core. In the same low power field with bright nebula N6726, N6727, N6729 to the SE!
13": bright, large, mottled, many faint stars resolved across disc and at edges of halo.
8": bright, large, bright core, mottled, some resolution of extremely faint stars around edges.
N6749 = Be 42 = C1902+018 = OCL-91 = Lund 876
19 05 15.2 +01 54 03
V = 12.4; Size 6.3
17.5" (7/1/00): very faint, very low surface brightness globular in a dusty portion of the Aquila milky way (dimmed by at least 4.5 magnitudes of extinction). The core is 15"-20" slightly brighter spot less than 1' SW of a mag 12 star. The surrounding halo is just a weak glow with averted vision, 2'-2.5' in diameter with an ill-defined edge, and just brighter than the milky way background. The glow encompasses the mag 12 star on its northeast side but does not reach two mag 13.5 stars off the south side. This cluster would most likely be overlooked if just quickly scanning the field.
17.5" (7/24/95): very faint, ~3' diameter, unusually low surface brightness for a globular cluster with only a very weak central brightening. A mag 12 star is superimposed on the N side and two mag 13.5 stars are at the S end (not members). The core appears to be located ~1' SW of the mag 12 star. Does not appear like a globular but rather a diffuse nebula in a rich milky way field. Difficult to determine exact outer extent.
13": extremely faint, moderately large, very low surface brightness and fades at high power. Near the visual threshold this is one of the two faintest NGC globulars along with N6380. Estimate V = 14. Located at the NW edge of an elongated group of six mag 12/13 stars and 25' ESE of mag 5.8 SAO 124203. The position listed in the NGC, SC2000, N2000, U2000, and DSFG are all about 7' too far S.
This cluster is attributed to John Herschel (h2029) but his description "a cluster of loose small stars of various magnitudes; fills the field." appears to describe a larger clustering (possibly including the globular). Listed in the Lynga catalogue as an open cluster = Berkeley 42. The position given in SC2000, NGC, L&S, N2000, U2000, and DSFG are all wrong, mostly in declination by ~7'.
Terzan 7 = E397-SC14
19 17 44 -34 39.5
V = 12.0; Size 6.0
17.5" (6/30/00): at 220x and extremely low surface brightness glow, ~1.5' diameter, was visible. A couple of mag 14.5 stars are just off the following edge and a mag 15 star or knot is at the W edge. The edges of the halo are ill-defined.
17.5" (7/20/98): picked up at 220x as a very faint glow with weak concentration, perhaps 1.5' diameter but surprisingly easy for such an obscure globular (brightest of the Terzan catalogue) At 280x, two mag 14 stars are at the E edge [closest is 35" ESE of center] and a mag 15 star is symmetrically placed at the WNW edge. The globular has an irregular surface brightness with a fleeting glimpse of a couple of stellarings superimposed. Two brighter mag 12 and 13 stars are off the SW and SE sides. Located 4.4' W of a mag 10 star.
Terzan 8 = E398-SC21
19 41 45 -34 00.0
V = 12.4; Size 5.0
17.5" (6/30/00): at 220x appeared very faint, round glow, just 1.2' diameter. The surface brightness is irregular with a couple of extremely faint stars involved.
17.5" (7/20/98): at 220x initially appeared to have a small bright core surrounded by a very low surface brightness halo 1.5'-2' diameter (boundary difficult to trace) within a rich milky way field. With concentrated viewing, I noticed a couple of close mag 15 stars just SE of center contributed to the impression of a small bright core and the background glow was otherwise unconcentrated. The cluster is surrounded by several mag 13 and fainter stars. More difficult to view than Terzan 7 also observed on same evening.
N5998 = E450-?019
15 49.5 -28 36
Size 6
17.5": this asterism appears as a faint, elongated group of 9 stars. Most of these stars are arranged in an arc concave to the NE. Appears fully resolved and too poor to be a cluster.
N6400 = Cr 342 = Mel 177 = Lund 767
17 40 13 -36 56.9
Size 8
17.5" (6/30/00): ~50 stars are resolved in a 8'x5' region at 220x. The stars are fairly uniform in brightness though irregular in outline. The cluster is elongated N-S with a nice string extending through the cluster to the SSE and NNE with a slight bend near the center. At the kink in the string is a denser clump of stars. There are circular voids on the NW and SW ends. The two brighter strings (on the following side) and two less distinct rows of stars create a vague "X" shape through the cluster with a close loop on the north end.
8": faint, fairly small, fairly rich. Many stars are aligned in rows.
N6694 = M26
18 45.2 -09 24
V = 8.0; Size 15
17.5" (6/30/00): this rich, distinctive cluster stands out well in the field at 100x. At 220x, ~60 stars are resolved in a 7' diameter. A mag 9 star marks the SW end. About a dozen stars are arranged in a striking arc (concave to the west) just north of the mag 9 star. A dark lane oriented N-S bisects the cluster just following this star chain and extending past the bright star. On the east side of this lane is a rich group of stars, roughly arranged into two irregular ovals.
13": about 40 stars mag 9-14 are resolved in a 7' diameter at 220x. The brightest star is mag 8.8 SAO 142584 at the SW end. A faint group of mag 13.5-14 stars is just east of the main section. Located in a rich field.
8": 20 stars mag 11-13, fairly small. Consists mostly of faint stars except for the four brighter central stars which form a "kite" asterism. Some dense sections of faint stars lie N and S in strings.
N6811 = Cr 402 = Mel 222 = Lund 897
19 38.2 +46 34
V = 6.8; Size 13
17.5" (7/1/00): this a large, beautiful cluster at 100x. The central section is ~8' in diameter, roughly triangular and contains a scattering of ~20 10-11th magnitude stars. There are no prominent members - the brightest star (at the west edge) has a faint companion. Perhaps 85 stars are resolved in the unconcentrated central region (there is nearly a void in the center) over haze. The richest knot of stars is on the NE side. An isolated 5' tails of stars extends NW and another curving string of stars can be traced 8' to the east.
13": fairly large and rich group of approximately 60 stars including many mag 11-12 stars. A long trail of stars follows and a bright group of stars is WNW.
N6819 = Cr 403 = Mel 223 = Lund 900
19 41.3 +40 11
V = 7.3; Size 5
17.5" (7/1/00): this is a rich, beautiful cluster at 100x. The central 6' contains 80-90 stars over unresolved haze and has an irregular outline with the brighter stars forming a squared off "U" shape open to the north. The cluster extends to ~8' diameter with many faint stars on the SW side. The outline appears elongated SW-NE with the inner bars of the "U" on the NE border delineating a distinct border.
13": over 40 stars resolved at 166x including two intersecting strings. Striking very rich group situated in a rich star field. A mag 10 star is off the SW end and several bright stars are in the field at low power.
8": rich, well-resolved, pretty.