Observing location: Sedona, Arizona, USA (1368 meters / 4488 feet)
NE Lim.mag: 7.0m (zenith)
SQM-L: 21.00 (zenith)
Background sky: 7 (good)
Seeing: 7 (good)
Transparency: 7 (good)
Weather: +26.0 - 21.0°C, humidity 28%, clear.
I had a mix of some interesting objects for the almost last night of the trip. I had forgotten all about IC 4628 in Scorpius so I started it that and the nebula wasn't difficult to spot as an E-W elongated puff in a rich field of stars. I also humbled to sketch the large cluster Collinder 316, pretty much sketching everything I could see with the 40mm eyepiece (98' fov). Looking at the area after the fact, it seems like a big mess. Uranometria shows Cr 316 as a superimposed cluster surrounding Trumpler 24 with smaller clusters vdB-Ha 205 and Ruprecht 122 inside it. My SkyMap (updated cluster data of Dias et al.) shows vdB-Ha 205 with somewhat curious name of BH 205 and Ruprecht 122 as BH 202. It also includes three(!) additional clusters inside Collinder 316: ESO 332-08 (which I noted as a concentration of Cr 316), ESO 332-11 and ESO 332-13! Quick clean up is in order so vdB-Ha 202 = Ruprecht 122 (1975 vs 1967 discoveries respectively) and the ESO clusters are probable cluster candidates. And Uranometria was right, no surprise there.
|NGC 6506 field|
Next in line was supposedly one tough trio: two Terzan globular clusters and a Palomar. I began with Terzan 10 as it was close enough to the previous clusters. I routinely sketched the field and with averted vision could a few times saw a very faint, tiny nebulous patch just NW from a roughly 12th magnitude star and I marked this as Terzan 10. Wait, back up! Is this the same globular cluster Barbara Wilson has failed to see with a 20 inch telescope? Yes, the very same. Then, is there even a remote possibility that I actually saw it from a location such as Sedona and with an 4 inch aperture? I'm not going to say I saw it just based on this single observation but I'm going to give you a few things to chew on:
1.) I sketched the cluster perfectly to the correct position @ 304x
2.) There apparently a very faint pair (~15th magnitude) of stars just in front of Terzan 10.
3.) Terzan 10 is placed way off in SkyMap (surprised, anyone?).
|Terzan 5 field|
And then came Palomar 6 (by the way, this globular cluster includes the planetary nebula JaFu 1 in case you didn't remember). Despite its apparent faintness (if you can call it that) it was easier to see than Terzan 5 and appeared as a faint, round smudge in a rich star field with dark nebulae. After a success with Palomar 6 I went on to sketch Palomar 11 - again. Then I got back to even more familiar territory with open cluster NGC 6604 which I saw more of a large cluster with two concentrations than the tiny 5' cluster listed as NGC 6604. I really took a liking with this field which includes the emission nebula Sh2-54 in the background. NGC 6818 showed a definitive ring structure and Messier 75 two "bars" extending from the bright core.