Hi all . . .
The span between the western (leading) fringe of the LMC and the shallow triangle of Mensa’s base—basically the two-degree band between 74° and 76° South—contains a boggling 35 faint globulars and open clusters. None are marked on my 1988 edition of Uranometria (charts 462 & 463). None of them appear on the Michael Vlasov charts that I use in the field. The only downloadable charts that give any clue of the profusion of faint LMC globulars in Mensa are the 10 shown on Chart 217 of
José Torrés B set (DSOs down to visual mag 14), and Chart 558 of
Torrés’s chart set C (DSOs to mag 15.5). I’ve attached a clip from the Torres C set.
The last dark cycle here in SA saw several cold fronts move through, yielding spectacularly clear, still skies afterward. I managed to spot all 10 of the Torres C chart GCs in a 180/1800 Mak using 20mm and 9mm eyepieces. These clusters take a lot of patience. They are all in the mag 12.3 to 13.8 range—about on par with the five Fornax Dwarf GCs. Even with mag 7.3 and sub-arcsec skies, I had to look steadily at the spot where the Torres chart located the cluster to be. Typically I would see only a handful of faint glimpses wavering in and out at the object’s position across fifteen or twenty minutes. By way of comparison, E3 (ESO 37-01) in Chamaeleon recently reported here on IIS was visible steadily though faintly on the same evenings. IC 4499 in Apus was as easy as a mainstream globular despite its low surface brightness, and I could pick out 10 to 12 of its stars at any given moment. I repeated the Mensa GC set 4 different nights during the dark cycle, so they are sufficiently reliable observations to log.
If you spot any of these, go back and scan that section of the sky from -74° to -76° S at high enlargement using WikiSky. There are an amazing number of fuzzy dots ranging from obvious globulars to inconspicuous smudges with a telltale fuzzy edge. I got tired of counting at 35 globular-like concentrations. This is the same number of globulars as in the entire constellation of Sagittarius!
NED and Simbad have very little on these objects besides basic position and luminosity. A peruse of the arXiv and ADS papers don't come up with much on the LMC GC set south into Mensa. There's very little LMC extinction or starform activity in this area, so I'm wondering where these GCs were during the 10 or so million year period during which the LMC crossed the MW disc. The LMC leading edge halo gas must have been tidally stripped almost completely, leaving the GCs in the clear.
I'd love to have Robert and Paddy chime in on these objects. I don't think I've seen a report on them elsewhere, pretty much ignored in the professional papers, and a fun track-down for you & me. I'll be after them again this coming cycle, this time with a 200mm Mak.
Cheers from Dana in S Africa