During the week of July 19-24, I was involved with the San Francisco State course on Observational Astronomy which takes place at their Sierra Nevada Field Campus on Highway 49 near the Sierra Buttes. I've participated as a teaching assistant since 1988 along with friends Jim Shields and Ray Cash, helping out the students with assignments during the afternoon and lending our 17.5" scopes for astronomical observations in the evening. This year my 16-year old daughter, Andrea, enrolled in the class and we also brought along her 10" f/5.6 reflector.
The evening observing sessions generally run until about midnight and then Jim, Ray and myself often pull out our star charts and work on pet projects (Hickson compact groups, Abell galaxy clusters, obscure planetaries, etc.) that require the pristine skies accessible at this 7200' Sierra site. This year our observations were limited by clouds on Tuesday and Wednesday, but I did track down a number of challenging targets in on Monday night.
A few months back while looking up an article at the astronomy library of UC Berkeley, I ran across a series of articles in Astronomische Nachrichten (a venerable German astronomical journal which announced many of the early NGC discoveries) on Shakhbazian compact galaxy groups. These distant groups were catalogued in the 1970's in a series of articles but are little known to amateurs since most of the galaxies in the groups are 18th magnitude or fainter. But Jim, Ray and myself have been working carefully through the challenging Hickson catalogue of 100 compact groups of galaxies and were looking for another extreme challenge.
Leafing through the Digitized Sky Survey images in the A.N. articles one of the most promising visual targets appeared to be Shakhbazian 166, which is also catalogued as UGC 10638 and described as a linear chain of 11 galaxies in Ursa Minor. Several of the individual members (which are virtually stellar on the DSS) are catalogued in the Morphological Catalogue of Galaxies (MCG), but their positions are too rough to sort out the individual identities. In any case armed with a Guide Star Catalogue chart of the field this was one of first targets when the astronomy class ended on Monday night.
Once the field was identified on the GSC chart, two or three faint galaxies were immediately seen at 220x. Several minutes of carefully scrutinizing the area at 280x reveal a total of five members in a chain less than 7' in length oriented SW-NE! All of these galaxies appeared as 15"-25" round "knots" of approximately 15th magnitude and hidden among a number of faint field stars. The brightest member is catalogued as MCG +14-08-017 = CGCG 367-021 as is situated 50" following a mag 13 star. A couple of these objects required averted vision to glimpse so I made a unbiased sketch of the entire field to later sort out the sightings on the DSS.
Y-C 2-32 is a little known 14th magnitude stellar planetary in Sagittarius which escaped discovery until 1973. Situated close to the ecliptic at 18 55 30.7 -21 49 40 (J2000), it's not plotted on the Uranometria but was identified at 220x using a GSC finder chart of the field. It appeared as a mag 14 "star" just 1.1' WNW of a mag 12.5 star. Using the OIII "blinking" method, the object was immediately identified at 140x as a planetary due to its excellent contrast gain as the planetary appears significantly brighter than the star close following (gain of ~3 magnitudes). The image was completely stellar at 280x.
Lyra is not a constellation you generally go galaxy hunting but I've logged 32 galaxies here, a number of which were missed in the dense milky way fields by the Herschels and other 19th century visual observers. One of these relatively bright non-NGC/IC galaxies is UGC 11428 which is situated in a rich milky way field one degree north-east of M56 at 19 20 28.6 +30 49 33 (2000). Once the field was identified this object appeared as a faint, round glow, 1.0' diameter with very weak concentration. With extended viewing the surface brightness appeared a bit irregular with a couple of brighter spots.
As the seeing was quite good and transparency easily better than mag 6.5, I decided to go after several globulars. NGC 6366 is a faint, low surface brightness globular in Ophiuchus, perfect for these conditions. At 220x it appeared as a diffuse irregular glow, ~4' diameter, with only a weak concentration. Two mag 9 and 10 stars were off the west side, the nearest is less than 4' from center and a closer pair of mag 11.5-12 stars resides [45" separation] at the S edge. There were perhaps a half dozen faint but obvious stars visible over the ill-defined glow and roughly a dozen stars with careful viewing. At 280x, the cluster was pretty clumpy and starting to really break up into numerous very faint stars. Roughly two dozen stars could be glimpsed with averted vision down to 16th magnitude. The full extent of the cluster was difficult to trace but extends beyond the central 4' region.
Next on my observing list were a couple of Palomar globulars which I had last observed nearly 15 years ago with a 13" Odyssey I. These 15 globulars were found by George Abell, who had early access to the POSS, and are generally very distant or very low surface brightness. Surprisingly, the Sky Catalogue 2000.0 states "The remote outlying globulars possessing only Palomar designations are too dispersed and faint to be seen at all." Not true.
The first target was Palomar 9 which was actually discovered much earlier by William Herschel and received the designation NGC 6717. This object appeared as a very unusual small, faint glow just 2' south of mag 5 Nu 2 Sagittarii! The very faint background glow is ~1' diameter but more notable are several superimposed stars. A close pair of mag 13.5 stars is at the NE edge 25" from center and a similar star is at the WNW edge 20" from center. There is a very small bright core which on closer inspection appears to be a close pair of mag 12.5 stars or possibly a bright stellar core and nearby star. Other than the central "knot", the unconcentrated 1' background patch has a low surface brightness and is much smaller than the listed diameter of 4'.
Palomar 8 is a fairly faint, round glow with an irregular surface brightness located 2.6' WSW of a mag 11 star. A few faint stars were visible around the edges including a mag 14 star at the south edge and a close trio of stars off the east edge. A very faint mag 15 star is at the west edge which appears a bit clumpy and a few threshold glimmers popped in and out of vision at 280x. With averted vision there was a hint of resolving a few mag 16+ stars along the W side.
After success on the Palomar globulars, I pulled out my finder charts on a couple of Terzan globulars in Sagittarius. This short list of 10 globulars was compiled by Terzan in 1971 and again to quote Sky Catalogue 2000.0 "are detectable only in the infrared because their visible light is so highly attenuated by interstellar dust." Nevertheless, the DSS red light image of a couple of these globulars looked promising and Terzan 7 in Sagittarius at 19 17 44 -34 39.5 (2000) was next up.
Regardless of the Sky Catalogue 2000 comments, this one was pretty easily picked up at 220x as a very faint glow with weak concentration, perhaps 1.5' diameter. At 280x, two mag 14 stars were visible at the E edge [closest is 35" ESE of center] and a mag 15 star was 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.
Flush with success I went after Terzan 8, a more challenging globular at 19 41 45 -34 00.0 (2000). Viewing at 220x revealed 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 extended viewing I could see there were a couple of mag 15 stars just SE of center which 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. At this point I called it an evening and packed up to head back to the field campus with starry memories to dream about.