Summer Clusters and Nebulae

18-19 May 2020, 23:45 – 2:30

Conditions: Breezy, relatively mild (first night I haven’t needed my winter coat). After a day dominated by high cirrus, the sky cleared suddenly, with just a few lingering vapour trails crossing the sky. Cloudy later on.

Seeing: Average - poor
Transparency: Poor - average

The nights are so short now that it doesn’t get reasonably dark until after 11pm, which makes for a lot of hanging around in the evening when (like tonight) the clear-sky forecast is ambiguous. With the sky near the northern horizon staying noticeably light, and vapour trails drifting overhead, the seeing and transparency varied considerably from minute to minute and from one part of the sky to another.

After warming up with M12 and M10 (both clusters looked a little hazy tonight), I tracked down another lesser-known globular in Ophiuchus:

NGC 6426, globular cluster, Ophiuchus
133x. Very faint hazy patch; a little condensed with averted vision. Unimpressive.

NGC 6572, planetary nebula, Ophiuchus
133x and 171x. Small, very bright oval disc; almost stellar at 133x. Stands out largely because of its strong green-blue colour. At 171x, the central star or core region (it was hard to tell exactly what I was seeing) overwhelms the surrounding nebulosity in direct vision. In averted vision the opposite is true: the outer nebulosity becomes the dominant feature.

NGC 6633, open cluster, Ophiuchus
133x. Follow-up from previous observation. Loose cluster of bright stars elongated roughly N-S. As noted previously, shows well in finder. Small “arrowhead” asterism of about 8 stars separated from main cluster on western (leading) side. Quite large, but a bit more “telescope-friendly” than the nearby IC clusters 4665 and 4756.

IC 4756, open cluster, Serpens
133x. Not as bright as IC 4665 and NGC 6633, but a very rich, very large cluster – best suited for smaller wide-field scopes.

NGC 6791, open cluster, Lyra
133x. Faint, extended haze. Starts to resolve with averted vision, giving at least a sense of its richness. Not much, if any, improvement on my previous observation, but I am slowly warming to this cluster.

M56, globular cluster, Lyra
133x. A little washed-out compared to previous observation. The triangular core was less apparent tonight, but I did notice a bright star leading the cluster and a long “x” shape of stellar arms.

M57, The Ring Nebula, Lyra
171x. Additional prep work for sketch (first draft below). The transparency must have been good in this part of the sky because I could just about detect a faint 14th magnitude star east of the ring (just beyond the brighter 13th magnitude star).

At 1:20 I was distracted by the unmistakable sight of the ISS passing high overhead.

After quick looks at M27, M4 and M80 I was irresistibly drawn to an old favourite:

M11, the Wild Duck Cluster, Scutum
133x. After all these years it still boggles me that I don’t have to travel any further than my back garden to see something as breathtakingly beautiful as this cluster. I have mixed feelings about the bucket list approach to life, but if you insist on such a checklist, seeing M11 through a telescope should probably be on it.

At around 2 AM the clouds returned with reinforcements, but after I’d taken the scope indoors – wouldn’t you know it – the sky suddenly cleared again from the south, and now it was remarkably free of haze. With only about half an hour of usable dark left, it wasn’t worth carrying it back out again, so all remaining observations were carried out with 7x50 binoculars and the naked eye (the most important instrument of all!).

M24, star-cloud, Sagittarius
I don’t recall ever seeing M24 with the naked eye before (the Milky Way in Sagittarius is always a little washed out from my location), but tonight it was visible as a hazy patch, a little smaller than the Scutum star-cloud further to the north. The binoculars revealed it to be sprinkled with stars, the brightest ones forming a distinctive almond shape.

This part of the sky (the steam rising from the spout of the Sagittarius teapot) is rich in bright clusters and nebulae, many of which showed up well in the binoculars (particularly M8, the Lagoon Nebula). Also visible in the binoculars were M12, M10, M11 and M27.

The binoculars resolved several more stars in M6 tonight, giving a much better view than 17 May. I also got my first glimpse of M7, which was just visible as a faint hazy patch very low in the south. I propped my elbow against a door-frame to steady the view and over time a few faint stars began to pop out. Averted vision also showed the cluster to be larger than was first apparent. From the same vantage point I could also see the bright stars Lambda Scorpii (Shaula), Upsilon Scorpii (Lesath) and G Scorpii through the binoculars (but not with the naked eye), all three of which culminate at less than 2 degrees above the horizon from my location. I don’t think I’ll be able to get the XT10 on M7, but it might be possible in the TV60.