9:50 p.m. 6 July 2002 PDT (2002–07–07–0450 UT)
It has been a while since I've made it up to Lockwood (the Los Angeles Astronomical Society's dark sky observing site), and even the threat of partly cloudy skies didn't deter me from driving out. Sad to say, the skies carried out on their threat. Clouds swept through overhead all evening, and there were few spots in the sky that got down even as deep as magnitude 6.0.
Even so, I was able to get some decent observing in, while other observers were busy pooh-poohing the mediocre sky. I brought both Opus (my 5-inch SCT) and my 1-year-old 10-inch Starsplitter along, both to compare views and also pinpoint the location of some dim objects in the eyepiece.
I first pointed the Starsplitter to M4, and admired the view in the 55 mm Plossl. It's the only eyepiece I have in which M4 looks normally sized; in all the others, it looks monstrous. From brighter skies, or in smaller apertures, the north-south streak is the predominant feature, but in the 10-inch, one sees so many stars, and so well resolved, that the feature is paradoxically not as prominent as it might be.
Viewing M4 reminded me that there was a second globular in the area, closer to Antares, and that might be a good first new observation. So I consulted the new Uranometria, which I also brought along, and identified the second cluster as ninth-magnitude NGC 6144. It is only about a half degree west-northwest of Antares, making it less than half as far from that rival of Mars than M4 is. I could make out only a single tenuous feature: a slight striation from east to west. The glare of Antares made this a moderately difficult object, even in the 10-inch. I had to take care to place Antares out of the field of view, and even then there was some glare. It was not much harder in the C5+ (in which I could also see the asymmetry), which I guess I might attribute to the superior baffling of the SCT. Well, maybe that's a project for another time.
Next up was an open cluster: NGC 6791, magnitude 9.5. It can be found reasonably easily, close to 21 and 22 Aquilae, and about as far from delta Aquilae as Vega is. In the 5-inch SCT, it was a dimly but easily seen unresolved blur, which to my mind underscores the richness of this cluster. The 10-inch showed it as a brighter and more easily seen blur, still unresolved, but with quite a deal of granularity. Uranometria notes that the DSS image shows it as a sparse globular, and I can easily believe it based on how it appeared in the eyepiece.
The third shared target for the night was the most difficult, NGC 6118. The saving grace is that it is probably one of the easiest to find. It makes an elongated isosceles triangle with Yed Prior and Yed Posterior in Ophiuchus. About twice as far northeast of either of those stars as they are from each other is a miniature version of Sagitta, and magnitude 11.7 NGC 6118 is just off the brightest star that marks the arrowhead. The 10-inch showed it, after a minute or so of hunting, as a dim oval blur, about twice as long as it is wide, and elongated roughly northeast-southwest. That "bright" star marking the arrowhead is actually only magnitude 6.2, and I had to be sure to place it out of the field of view, much as I had done with Antares on NGC 6144! This galaxy appeared somewhat brighter toward the center.
In Opus, the galaxy appeared only intermittently, and I had to make sure that I really was seeing the same thing over and over. One curious thing is that it seemed somewhat more elongated in the smaller scope than in the larger. I wonder if the brighter center is perhaps more stretched out in visual appearance than the outer periphery. I do know that the moments of better visibility coincided with those times when the clouds left that small patch of sky, and the limiting magnitude extended perhaps to about 6.0.
One aspect of this night's observing that surprised me was the seeing. Generally speaking, I get much better seeing in the city than I do up at Lockwood, almost as though it were some sort of compensation for all the light pollution. Lockwood may have seen fit to provide its own compensation for the clouds by yielding sub-arcsecond seeing, a real rarity. Even with only so-so collimation, the Starsplitter cleanly split zeta Bootis, its Airy discs almost exactly touching each other—just as you'd expect for a binary of that separation in this aperture. The C5+, in comparison, only showed an elongation and, at a few moments, a "breadloaf" profile.
My last comparison object was Caroline's Cluster, NGC 7789 in Cassiopeia. This is a beautiful object, but it only shows well in reasonably dark skies; it is hardly visible at all at home. The difference between the 10-inch and the 5-inch was rarely more in evidence than on this rich open cluster. The SCT showed it as a diaphanous blur, definitely brighter toward the center, definitely rich, but only showing a dozen or so pinpricks of individual stars. In the 10-inch, on the other hand, it was revealed as the open cluster it is, with numerous stars dotting its entire area. What a beautiful sight!
Speaking of the 10-inch, I've had it for a year now, which means that I have to select a name for it. Despite a handful of clever suggestions from sci.astro.amateur, I chose to go it alone on this one, and I hereby christen it Mr. Snuffleupagus—Snuffy for short—drawing from its prominent proboscis, as well as its propensity for showing up when only a few people can see it, so that quite a few people might not believe it actually exists. But believe me, it exists!
Copyright (c) 2002 Brian Tung