1:00 a.m. 9 December 2004 PST (2004–12–09–0900 UT)
I slept a couple of hours earlier in the evening, and decided to head out into the chilly night to do some observing. I purchased a new eyepiece—a 24 mm Tele Vue Panoptic, easily the most expensive eyepiece I own—and as expected, was rewarded with a week or so of consistently cloudy weather.
But tonight was clear. I wanted to see the new comet, Comet Machholz C/2004 Q2. At the present time, it is heading northward through the western portion of Lepus; a map is available in the January issues of both Sky and Telescope and Astronomy.
I warmed up by taking a quick peek at M42 and M41. The Panoptic is a wonderful eyepiece, framing M41 beautifully while still achieving a pleasingly moderate magnification (about 32x with the focal reducer in place). The 32 mm Plossl has the same true field of view, so it can frame the cluster just as well, but its magnification is lower and the cluster seems somewhat less grand in it. My 25 mm Kellner, on the other hand, has the same magnification, more or less, but its field of view is noticeably smaller, and the cluster just isn't framed nearly as well.
Comet Machholz is considerably brighter than I expected. My sky was bright (ZLM about 4.6), so I may be underestimating its brightness, but even so, I estimate its magnitude at about 5.5 or so. The coma was large and diffuse, maybe 20 to 30 arcminutes across (again, possibly underestimated because of sky brightness), with a noticeable brightening toward the center. I couldn't see any tail, but then, the comet is near opposition.
While I was up, I decided to run through three open clusters: NGC 2184, NGC 2232, and NGC 2260. These objects proved to be a lesson in how atlases can deceive you in regards to how distinctive clusters will look in the eyepiece. One gets the impression from both Uranometria (limiting magnitude 9.75) and PleiadAtlas (limiting magnitude 11.5) that NGC 2184 is a so-so object, with NGC 2232 and NGC 2260 surpassing it.
This turned out not to be the case. NGC 2184, against my expectations, proved to be a delightful object in the eyepiece, with some two dozen stars showing fairly easily over a patch about three-fourths of a degree across, elongated slightly east-west. Its dimmer stars are grouped together near the center of the cluster, giving it a modest three-dimensional effect, as though the dim stars were the back side of a transparent globe.
NGC 2232, on the other hand, has (at least, under my current skies) the same sort of problem that M44 does—a nice layer of bright stars, but then a gap in brightness, so that the dimmer stars are at least a couple of magnitudes down the ladder. It gives the cluster a sort of hollow feel to it—a bright object, easily found enough, but without the pleasing distribution of stars that NGC 2184 has. It is also large, about as wide as NGC 2184, but seems broken into two pieces, one toward the northwest, the other toward the southeast.
NGC 2260 is the smallest of the three clusters. It is centered on a star at the end of a short northeast-southwest row of stars, and is fairly dim, though not as dim as the second layer of stars in NGC 2232. It was kind of frustrating observing this cluster, and I found myself wishing I was seeing it under better skies; I'll have to remember it the next time I get under a dark sky.
I closed with M42 again, but this time with the 6 mm Radian (130x). I thought the seeing was pretty good, so I was hoping to glimpse the F star in the Trapezium, but even the E star was only intermittently visible. F, as you might expect, was nowhere to be seen. I think the transparency (or lack thereof) was more to blame for the invisibility of F.
1:00 a.m. 11 December 2004 PST (2004–12–11–0900 UT)
I took a look at Saturn today, but the seeing would support it. The Cassini Division was visible, but there was no shading in the outer A ring, and certainly no sign of the crepe ring. On the other hand, the E and F stars of the Trapezium were visible every now and then. The seeing wasn't that bad, I suppose.
In any event, it still leaves open clusters. First up was NGC 2331, a cluster about halfway between Castor and Mebsuta (epsilon Geminorum). When plotted in Uranometria, it is entirely blank—not a promising sight. PleiadAtlas is a bit more encouraging, showing about a dozen or so stars down to magnitude 11.5.
That's reasonably close to the truth. Better yet, however, is that there is a nice veneer of stars barely visible through Opus (under magnitude 4.6 skies), that shimmered in and out as I moved my eye this way and that, as a result of averted vision. It's a magical effect that I've noted previously with M22, the wonderful globular in Sagittarius, but this is the most distinct I've seen it with an open cluster. Both the brighter stars (as bright perhaps as ninth magnitude) and the fainter ones are elongated north-south, suggesting that they're all connected.
Another cluster in Gemini is Collinder 89, an even larger cluster at the feet of Castor, near M35. It's punctuated by a number of fairly bright stars (one as bright as fifth magnitude, I think), but it's so spread out that it shows up much better in the finder even than in the 24 mm Panoptic (I took out the reducer, so this eyepiece now shows a 1.3 degree field at 50x). And unlike NGC 2331, it doesn't have a lot of depth.
I closed out with NGC 2392, the Eskimo Nebula. This really is one of the better planetary nebulae up in the sky right now. Granted, it's a bit small, but not too small; the bright, central portion is maybe a dozen arcseconds across. And it is fairly bright—even brighter than the star it's next to, so it's easy to find and see, to boot. Look longer, and you can see a fringe of dimmer light around it. It's a wonderful sight.
Copyright (c) 2004 Brian Tung