It’s been a wet winter here in S Africa. Hardly a decent night since June. July rained. August saw -17° C and frost on the aloes bushes. September dark moon was clouded out. I was getting practically horny for a fling with the heavens. Finally on the 7th of October I made it up to my dark site again. Weltevreden Farm is in the Karoo highlands in central South Africa, -31°8587 S, 24°4403 E. At 1430 meters, this region was one of the two candidates for what is now the Sutherland complex of visual and radio observatories. Sutherland was close to Cape Town, while the Nieu-Bethesda region where I go is nowhere near anything. The universe is more accessible than any human activity. Zero light pollution. No one but me, 300 sheep, assorted jackals and kudu, night birds of a myriad songs, and frogs in a nearby pond that are sound’s equivalent to light pollution. Weltevreden Farm is so dark that my hand casts a shadow of the Milky Way on the telescope tube even when the moon is at crescent stage.
This visit’s to-see list were some rarely visited globulars whose positions I found while perusing Jose Torres’
TriAtlas B set and Alvin Huey’s
Globular Clusters. Two are easy, two are fiendish, the rest are merely difficult. But they can be done.
I’m a purely visual observer using simple equipment — an Astro-Telescopes 152 f5.9 fitted with a Baader 495 Longpass filter, which completely suppresses chroma but allows the V and R bands though undimmed. I’ve visited ephemeral glows like the Pegasus Dwarf and Sextans B with and without the Longpass and can’t detect difference. My main scope is either a Santel Mak 180mm f/10 or Skywatcher 180mm f/15. The Skywatcher is better for difficult faint and small objects because it yields 180x with 15mm eyepiece and 270x with a 10mm. Recently I bought three of the new Meade 100° Megawides just to try them out. I found their lighter weight and resistance to eyecup dewing work better for me than my Explore Scientific 100° ware. Much as I respect what ES has done with their optical quality at a decent price, the eyecup dewing up is frustrating when there’s humidity in the air. The scopes are mounted on mounted on a side-by-side alt-az set on a simple steel tube pier with three old cast-aluminium legs from an old Meade mounting.
18:40 UT: The globular
ESO 452-SC11 near Antares. This thing is not even on the Torres charts. Yet it’s not hard to find. Makes a fuzzy quadrilateral out of a triangle of stars. Too low to see well given the crescent moon nearby. In the refractor it showed as a tiny hazy spot 3 times, steady in averted in the Mak. Easy to spot because of 3 mag 11 & 12 field stars in a row in front of it, boosts its apparent mag by 2. The cluster looked like a tiny haze patch, not a round cluster. This cluster makes a nice threesome if you start with M4 and then go to NGC 6144.
19:05 UT:
Ton 2 Named after the Tonantzintlia Observatory in Mexico. It is located near NGC 6380, often cited as “the second most difficult NGC globular”. That’s odd, N6380 has never seemed as difficult as its reputation suggests. There’s a mag 10.2 star right on the globular’s half-light radius. The globular makes the star look like a comet with a bright head & dim tail. So look for the star with the cometary flare; it’s the only one like it in the field. But Ton 2 is not at all in the same league. It IS very difficult. Look it up on WikiSky, then remove almost all the globular’s luminosity, and that’s what I see. It wavers in and out of visibility, showing as a feeble, even glow for a few seconds at a time and then goes below the scintillation threshold. It looks all of its 2.5 arcmins diameter, but is so faint there’s no hint of core concentration. The halo fades gently away into nothingness. It turned out to be the most difficult of all the clusters described here, though I have no trouble with it in my 180mm Mak if the transparency is good.
19:15 UT:
Pal 8 is surprisingly easy (Huey p.104). I’m surprised that I don’t see it cited much on the forums. See the attached finder chart. Follow the curved line of 4 stars that act as a pointer to Bernard’s Galaxy NGC 6488 in Sagg near Cap, but go the other way. Gauge the distance between the two stars that parallel the teapot handle, and double this distance on a line going straight away and parallel to the teapot lid toward M25. This cluster is brightest at about 60x in a 150mm scope or larger; it quickly loses its lustre with magnification. Look for an unmistakeable slender reverse-S chain of stars and Pal 8 is near the bottom of the chain on the teapot side. In the Astro-Telescopes 152mm with a 15mm 100° eyepiece, Pal 8 presents as a significantly reddened globular given the size of its core. The core is a flat luminosity profile about 4 arcmins in dia. The halo falls away rapidly, less than an arcmin thick. At 120x in the 180mm Mak Pal 8 seems much fainter. At this power Pal 8 presents as a soft, dim, granular glow with an abrupt fall-off to dark sky. It’s such a star-rich part of the sky the cluster seems almost an afterthought.
but when we use our imagination that is informed by what we know through scientific fact then what we are looking at is truly amazing. I am often in awe of just how magnificent our universe is and I find talking to people about it can lead to some great philosophical conversations. Often too I feel very insignificant but special when I realise just how small and fragile we are to exist within the great forces of the cosmos. We are blessed to experience what we can.
