OR Fall observing with the 48-inch
by Steve Gottlieb
Over the weekend of Halloween (October 30th), Howard Banich and I flew out to El Paso in the early afternoon, picked up a rental car and drove 3 hrs to Fort Davis in the remote
Davis Mountains, site of the Texas Star Party. The weather had been cloudy earlier in the week but was predicted to clear up on the day of our arrival (Thursday) as well as Friday,
but Saturday was listed as partly cloudy and Sunday was predicted to be cloudy and rainy. Still, as I've learned from several trips, the weather near Mt Locke is totally
unpredictable as the Davis Mountains strongly affects any incoming systems. The good news around sunset was the skies were perfectly clear. The bad news was a consistent wind. We
were able to observe for several hours, but it wasn't comfortable -- the scope was consistently bouncing in the winds, gusts would make observing high on the ladder uncomfortable -
particularly when facing into the wind, and seeing was -- as Jimi likes to say "Variable to Terrible". I believe around 3:00, we finally gave up as there was no sign of the gusts
letting up and the seeing was quite soft. Still we did get in some excellent views. The highlights from the first night included The second night (Friday) was by far the best night and we observed to 5:00 in the morning, although the seeing was generally only fair. Highlights included resolving stars in
Sunday was cloudy as predicted, but Jimi, his wife Connie, Howard and I took a road trip south to spectacular Big Bend National Park. We also had a scenic drive along the Rio Grande river, including a visit to Terlingua, which had just hosted the 48th annual International Chili Cookoff competition the day before. |
NGC 247 spanned at least 18'x5' NNW-SSE, stretching from an HII region at the NNW tip to beyond a mag 9.5 star near the SSE end. An interesting feature is a very large, elongated darker (dusty) region dubbed the "Needle's Eye" on the NNW side, extending at least 3.5'x1.0'. A relatively bright HII knot (identified in NED as MRSS 540-038059 from the "Muenster Red Sky Survey") is beyond this feature, 9.5' NNW of center. It appeared fairly faint, relatively large for an HII region, elongated ~N-S, 20"x12". A second well-defined HII knot is MRSS 540-038506, found 5' NNW of center. This easy patch appeared fairly faint, elongated, 15"x10". At least two small knots (including MRSS 540-038001) are on the SW side of the halo ~2.4' from center and ~1.5' E of a mag 12-12.5 star just off the west edge of the disc. Finally, I picked up a faint, very small knot, ~6" diameter, situated 3.5' SSE of center and 1.1' N of a mag 13.5 star. This HII region (not in the MRSS) forms a "double" with a mag 15 star 15" N. |
NGC 7793 is a bright showpiece galaxy in Sculptor, very large, oval 3:2 E-W, ~7'x4.5', large bright core. Spiral structure is evident, though it was difficult to trace individual arms except for one better defined arm attached on the west side of the core. This arm sweeps towards the east on the south side of the core (~2' from center) and ends just east of center. The halo is lumpy with an irregular surface brightness and several HII knots/associations are visible. The brightest individual knot is [H69] #20, from Paul Hodge's 1969 paper "HII Regions in 20 Nearby Galaxies", a fairly faint, 10" knot that was easily seen 1.5' S of center, near the south side of the halo. [H69] #27, a slightly smaller and fainter patch is near the WNW end of the halo (1.9' from center). On the WSW side of the halo are two additional close, faint knots, both ~8" in diameter; [H69] #32 situated 2.3' from center and [H69] #33 at 2.4' from center. Finally, [H69] #3/#5 is a fairly faint, 15" patch near the NW edge of the halo, 2.8' from center. A mag 12.5 star is just off the northern edge, 2.9' from center. |
We examined the large association NGC 206 carefully for resolved stars using the finder chart in Stephen Odewahn's 1987 study "A photometric survey of the rich OB association NGC 206 in M31". The 6 or 7 brightest members down to V = 17.6 were carefully identified with the brightest member #12 (V = 16.1) at the north edge relatively prominent. Then just scanning over the cloud with averted vision, roughly 20 additional extremely faint stars popped in and out of view, mimicking the appearance of a partially resolved globular cluster! Based on photometry in the paper, these extended down to approximately V = 18.3-18.5. The cloud, itself, was quite irregular and split up into several slightly brighter patches. I've labeled some of the brighter members which were individually identified on the chart. |
NGC 7656: at 488x and 610x appeared fairly faint to moderately bright, round, ~24" diameter, high surface brightness. Surprisingly, a low surface brightness wing or loop extending to the northeast was immediately noticed. This loop is brighter along the northern edge and passes through a mag 16.7 star (or stellar galaxy), increasing the overall length to 45" extending southwest (core) to northeast (loop). A mag 16.5 star lies 1.3' W and another mag 16.5 star is 1.4' N. 2MASX J23242536-1902139, an extremely compact galaxy (V = 15.7) lies 1.9' NW. Finally, 2MASX J23243030-1903019, an extremely faint quasi-stellar galaxy was glimpsed less than 30" NNW, although another loop in that direction was not seen. |
VV 186 = Arp 249 was clearly resolved into two cores at 488x, encased in adjacent halos. |
UGC 12914 and 12915, known as the "Taffy Galaxies" was observed at 610x. UGC 12914 (southwestern component) appeared bright, fairly large, very elongated 3:1 NNW-SSE, 2.1'x0.7',
sharply concentrated with a very bright, rounder core. The southern end of the galaxy gradually faded out and extended further than seen with my 24". A dust lane creates a sharp
light-cut off on the east side of the core and the diffuse glow from an arm is visible further east. A bright curving spiral arm is attached on the NNW side of the core and it hooks
north counterclockwise towards the companion |
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Arp 251 is a very compact triple system in western Cetus that was viewed at 610x. |
The brightest member of Zwicky's Connected Triplet appeared moderately bright, fairly small, round, 30" diameter, small bright core with a quasi-stellar nucleus. Flanked by a
"fairly faint" companion 25" SW, which appeared fairly faint, small, round, weak concentration, 12" diameter. An "extremely faint" 18th magnitude companion is 30" ESE (SDSS
J164931.14+452731.8), though this galaxy is not part of the Triplet. The third component, |
At 375x, Zwicky's "Boomerang" galaxy appeared as a very faint, fairly small, thin boomerang shape, elongated E-W. The galaxy curves in perhaps a 120° arc, concave to the north. Although the galaxy has an fairly even, low surface brightness with no core, the western tip is slightly brighter. A mag 16.5 star is barely off the east tip. Increasing the magnification to 610x and then 813x provided an excellent view. The Boomerang appeared mottled or slightly lumpy and was brightened slightly at both tips. There was a strong impression of several stellar quasi-stellar knots along the length. The mag 16.5 star was cleanly resolved off the eastern side. This galaxy is extremely blue with emission knots, and may be an extreme starburst galaxy. |
This N-S galaxy chain in Sculptor of length 3.4' is classified in the Arp-Madore category of "Interacting Quintets" and displayed in the Atlas (full page) in section 5.1. All 5
members were resolved at 375x and 488x. |
NGC 6670 in Draco is a fascinating interacting pair seen in this HST image. At 488x and 813x, |
The supernova remnant Cas A was one of the highlights this trip on the 48". We used 488x and a NPB filter to examine this SNR carefully. Immediately I noticed the nebula was much more extensive and detailed than previous views. The glow extending roughly 2.4'x0.8' E-W (twice the size seen previously) with the brightest section on the eastern half. At the west end the nebulosity faded and thinned as it curved WSW of a mag 13.5 star. The eastern half was quite irregular and brightest near the eastern end, where a couple of stars are involved. A very faint, but distinct filament (not seen previously) is attached at the east end and also extends E-W, just south of the main section by ~30". Overall, Cas A had a weak filamentary structure as opposed to a smooth glow, mimicking a piece of the Veil Nebula through a small scope. A short section of the southern rim was probably glimpsed, though I wasn't 100% certain of the observation (Jimi and Howard were). |