September 20 wasn’t as fine, observing conditions-wise, as the night that followed (written up previously), but it was perhaps more rewarding, in terms of the number of good observations made. Although I had observed many of these objects multiple times—several of them in early August at fellow AASIer Steve R’s house in Murphysboro, on a night beset with poor transparency/seeing/dew conditions—I chose to use this particular night to reobserve them and take better notes.
On this night, I was joined by the stalwart Bob M and Harry T; Steve R would arrive later with his 16 x 70 Fujinon binoculars. Harry (inspired by the astrophotography lecture given at September’s AASI meeting by the superb Dan C from Dardenne Prairie, MO) was experimenting with a DSLR, capturing an early-evening Iridium flare as he did so. Bob was getting in some final looks at the summer Milky Way with his 100mm SkyWatcher refractor/Celestron AVX combo. The high whine of the AVX mount was simultaneously soothing and disturbing—as always, the technology of the day confuses and frightens me. As usual, I was armed with the 12.5” Discovery and relied mostly on a 14mm 82* eyepiece for taking notes.
These objects (many of them Messier objects; all of them globular clusters) pushed me past the finish line of the Astronomical League’s Globular Cluster Program. I may be the first primate to have finished the program without logging Messier 13 in Hercules—an intentional omission.
My estimates of Shapley-Sawyer concentration classes were less accurate than usual. Part of this may have been due to the exceptional number of cars going past the parking lot on the night, their high beams blazing; we would later discover that a wedding reception was being held at the Lodge that evening. My recorded notes sound full of frustration and impatience with the constant stream of interlopers, and, likely, this affected my attention to getting the details right.
GIANT CITY STATE PARK VISITOR CENTER PARKING LOT
MOON: 26 days, absent
TRANSPARENCY: 6 (nice MW definition; Le Gentil 3 prominent even before darkness)
WEATHER CONDITIONS: temps in 50s-60s, moderate humidity (some dew), somewhat breezy
also present: RM, HT (later SR)
NGC 6517 (Oph)—not among brightest globs, but not tremendously difficult; sky not totally dark yet—3.5-4’ diam w/14mm—halo about 4’—inner 2.5’ considerably brighter w/point-like nucleus in averted—to S, arc of four stars, brightest to SF, almost a ‘Y’, when faint fifth star added—11th mag—not at all concentrated—CC 8?—not much if any granularity
NGC 6539 (SerCau)—much bigger than 6517—5’ diam—very diffuse—very little concentration—still early—on P side, 11th -10th mags star-pair about 6’ apart, one closer to cluster about 1 mag brighter than other—not much central brightening—middle 1/3 slightly brighter—w/averted, looks granular—star on edge of halo distractingly bright—CC 9-10 ?
M54 (Sgr)—pretty concentrated—6’—bright, 8th mag—granular on edges—at least middle 50% much brighter—to the SP is 9th mag star 18’ or so from cluster edge—CC 5?—no mistaking for anything but glob—to SF side of center is cluster star, maybe 12th, stands out, 0.5’ from center/edge of core
M55 (Sgr)–in all its diffuse glory—CC 11—ginormous—at least 15’—very open & diffuse—hundreds of stars visible—halo very spread out—middle 8-9’ somewhat tighter core—brightest stars form squashed pattern of trapezoid, like Teapot handle, with narrow end to F side and wide to P, brightest stars to SF—mag 7—bright star 10’ from halo to NP side—SF side looks like has “bite” taken out of it between brighter star and core, about 7’ across, looks like something obscuring; like apple with bite out—didn’t notice at first—rim of brighter 12-13th cluster stars on NP edge of bite which helps bite stand out
NGC 6712 (Sct)—large and diffuse, v. granular, number of halo stars—almost has two cores or figure 8 w/averted—cluster quite bright (8th mag)—core elongated P-F—7’ diam?—to NF side is bright field star (8-9th) mag about 7’ from edge of halo—brightest star in vicinity 15’ to due N—CC 9-10?—two brighter cluster members on F side, one on N edge of halo, other more embedded in cluster, pop more w/averted—surrounded by cloud of field stars to SF and P sides near edge of cluster
At this point I also digressed to find the planetary nebula IC 1295, in the same field, 21′ ESE from NGC 6712–visible with no filter, but much brighter with UHC and OIII filters.
NGC 6229 (Her)—bright (8th mag?)—forms (almost) equal tri w/two 7-8th mag stars to P side—to NF edge is another bright star—about 3.5-4’ across—CC 5?—quite concentrated—not quite granular or even on verge of it—tight core is 75% of cluster diameter
M71 (Sge)—v. loose—low end of CC (9-10? [10-11])—cluster is about 6’ across—dozens of starry points—8th mag—very flat on P side—“box” of 7-8 stars on S edge of cluster—on NF edge is 10-11th star, on SP edge is brighter star 5’ from edge of halo—core very irregular shaped, almost triangular, pointing to F side [lots of passing cars]
M56 (Lyr)—not little—bright, maybe 8th mag—very resolved, esp. w/averted—granular in core—7’—bracketed P-F by 8-9th mag range stars—core makes up inner 80%—almost tick-shape of 10th-11th stars across halo—CC 8?
M15 (Peg)—3rd on Messier list globs after 13 and 22 impression-wise—6th mag—not huge range of brightnesses in stars—2-3 gradients—halo stretches to 12’ or more—to S by 15’ from core is 7-8th mag star—high concentration, CC 4—beautiful center to cluster—ring of stars on edge of halo, then gap of several arcminutes, then another layer of stars—core only 2-3’, almost stellar—looks more crowded on P side, like a row of stars on edge, almost like shock front—halo squarish