Sierra Buttes and Lassen 7/20 to 7/27 (Globulars)

by Steve Gottlieb

Here's a batch of globular observations from both Lassen and the Sierra Buttes. Except for IC 1257 none of these are difficult objects but it was fun to view them at 435x and sometimes 565x in excellent seeing. Steve

NGC 5904 = M5
15 18 33.7 +02 04 58
V = 5.7; Size 17.4

18" (7/26/06): at 435x the cluster overfills the field and the intense 3.5' core is resolved to the center. The core has two easily resolved parallel star lanes oriented E-W that cross the core on the north and south sides and an extremely dense knot of stars is resolved on the west side of the northern lane. M5 was just visible naked-eye but the nearby mag 5 star (5 Ser) detracts from the observation.

NGC 6093 = M80
16 17 02.5 -22 58 30
V = 7.3; Size 8.9

18" (7/24/06): at 325x appears bright, fairly large, round, pretty symmetrical appearance, contains a blazing 1.5' core in a 5' to 6' halo. At 435x the halo and the periphery of the core are well resolved into roughly 100 stars and additional extremely faint stars pop in and out of visibility. The core itself is overlayed with a number of faint stars. Beautiful view at 565x as the cluster nearly fills the 7' field with stars from edge to edge with 100-150 stars and the core region is well resolved. The cluster appears asymmetric with the halo more extensive to the west (core offset to the east).

NGC 6144
16 27 14.1 -26 01 29
V = 9.1; Size 9.3

18" (7/26/06): at 325x roughly two dozen stars were resolved over an irregular, scraggly glow. A mag 12 star at the west edge is probably a field star. Very weak central condensation (concentration class XI) so the appearance does not look like a typical globular.

NGC 6171 = M107
16 32 31.9 -13 03 13
V = 8.1; Size 13

18" (7/26/06): beautifully resolved at 325x and framed by three mag 11.5-12.5 stars to the east, west and south. In the halo, roughly 35-40 stars were resolved and in addition the bright 1.5' core was partially resolved into a large number of densely packed stars. The cluster extends roughly to 6'x4.5', reaching the bright stars off the E and W side and elongated E-W at least 4:3.

NGC 6229
16 46 58.8 +47 31 40
V = 9.4; Size 4.2

18" (7/23/06): at 225x, appears bright, moderately large, slightly elongated, ~3.5' diamete with a blazing core. Several extremely fant stars pop in and out of view in the halo. At 435x a number of very faint stars are clearly visible in the halo (roughly two dozen) and the core is quite mottled with several brightness levels towards the center. The globular forms a perfect equilateral triangle with two 8th magnitude stars 6' W and 6' SW. While searching for N6229 I ran across a neat little asterism of 6 stars (Leiter 6) located 27' NNW that I had observed the previously month.

NGC 6235
16 53 25.3 -22 10 39
V = 10.2; Size 5.0

18" (7/24/06): at 435x this globular was quite scraggly with a small, irregularly shaped core surrounded by a much fainter low surface brightness halo extending to 3'-3.5' diameter. At least 15 to 20 stars are resolved with 3 or 4 fairly easy brighter stars but most are very faint, in the mag 15-16 range. With extended viewing, several extremely faint stars pop in and out of visibility in the halo increasing the overall total to 25-30 stars, though a lower number were visible simultaneously.

NGC 6287
17 05 09.3 -22 42 29 V = 9.3; Size 5.1

18" (7/24/06): this fairly faint 3' cluster was surprisingly partially resolved at 435x and 565x. At 565x the cluster was very lively and mottled with roughly 20 stars barely resolved over the disc (some popping in and out of visibility). The core was only weakly compressed. The cluster appeared on the verge of being well resolved with a number of extremely faint mag 16 stars sometimes momentarily sparkling and increasing the total to perhaps three dozen stars.

NGC 6341 = M92
17 17 07.2 +43 08 11
V = 6.5; Size 11.2

18" (7/24/06): at 435x the cluster overfilled the 9' field with several hundred stars resolved stars. The 3' to 4' core itself was highly resolved into roughly 100 densely packed stars (including a very compact knot of stars) with long streams of stars appearing to spiral out from the core.

NGC 6342
17 21 10.1 -19 35 15
V = 9.9; Size 3.0

18" (7/26/06): at 325x this small 2' globular was well concentrated to a a fairly bright 40" core. A mag 12.5 star is off the SW side of the halo, ~1.5' from the center. Perhaps a half dozen stars are resolved in the halo including three close stars on the NE side. Additional stars are sometimes visible in the WSW side and the N side of the halo. The core is very mottled and there is a strong impression of a couple of star lanes below the threshold of visibility. Located 70' SE of M9.

IC 1257
17 27 08.5 -07 05 35
V = 13.1; Size 1

18" (7/26/06): picked up at 225x, but viewed at 325x as a very faint, low surface brightness disc of 30" diameter with only a very weak central brightening. This challenging globular was visible steadily, even with direct vision but there was no hints of details. A couple of mag 16-16.5 threshold stars are close S and W.

NGC 6366
17 27 44.3 -05 04 36
V = 9.0; Size 8.3

18" (7/26/06): at 325x, 30-35 stars can be resolved with careful viewing in a 4' region with roughly two dozen of these generally visible and another dozen sparkling in and out of visibility. The resolved stars seem spread out over the entire disc which is only weakly concentrated. The outline of the halo is quite irregular and ill-defined and may reach to a larger extent. The cluster is bordered by several brighter stars which are clearly not part of the cluster. Located just 17' E of mag 4.5 47 Ophiuchi and faintly visible in 15x50 IS binoculars.

NGC 6638
18 30 56.2 -25 29 47
V = 9.2; Size 5.0

18" (7/22/06): at 435x this globular appeared fairly bright, ~3' in diameter with an intense 1' core. The core appears very mottled and just begins to break up into a swarm of faint stars, particularly around the edges. Several very faint stars pepper the halo and pop in and out of visibility. The halo has an irregular scraggly appearance. I was able to pick up this globular with 15x50 IS binoculars as a very small, faint glow along with a mag 9.4 star close S.

NGC 6712
18 53 04.3 -08 42 21
V = 8.2; Size 7.2

18" (7/23/06): situated in a gorgeous low power Milky Way star field at 115x with a dense background mat of faint stars filling the 45' field and planetary IC 1295 24' ESE. At 435x roughly three dozen stars are resolved in a 6' region, mostly on the western half of the cluster. The core is moderately bright but not sharply concentrated. The irregular halo is peppered with faint stars though at the periphery it was impossible to really distinguish from the numerous faint field stars that surround the cluster. A dark lane is quite obvious on the south side, appearing to detach the outer section of the halo on the SE side. The outer halo is poorly resolved on the eastern end.

NGC 7006
21 01 29.3 +16 11 15
V = 10.6; Size 2.8

18" (7/24/06): this small globular was viewed at 435x and 565x and it appeared very mottled and lively in excellent seeing. Two or three very faint stars were visible pretty steadily and a number of extremely faint mag 16 stars appeared to sharpen up and momentarily sparkle, particularly in the 1.5' to 2' halo. Perhaps a dozen stars total sparkle or pop in and out of view.

Observing Reports Observing Sites GSSP 2010, July 10 - 14
Frosty Acres Ranch
Adin, CA

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