11:30 p.m. 12 May 2002 PDT (2002–05–13–0630 UTC)
Tonight was the first time out for Opus in a while. (I have an unwritten report from about February on an excellent night for observing Jupiter, and one in March on a brief look at the Sun, but that's about it.) I decided to get gently back into the swing of things by looking at some old favorites.
With Bootes and Coma Berenices riding high in the sky, the obvious choice is M53, a spectacular globular cluster. It can be found close to alpha Comae Berenices, which is a dim star from suburban skies, not so easily identified, although I can find it directly west from tau Bootis a little more than one hour (a tad more than 15 degrees) in RA. I found M53 first with the 32 mm Plossl (39x), then put in the Vixen zoom for more detailed observation.
I find it continually puzzling that my observations of M53 are at once consistent with each other and yet inconsistent with what O'Meara sees. I see three spikes, extending out to the south, the northwest, and the northeast. And it's not as though I'm simply repeating my previous observations; I didn't confirm those until I just checked now to see that they were the same. It's clear we both see asymmetries, and yet my eye is putting the faint, not-all-there information I get through the telescope together in a different way. Photographs are no use—you really have to see it live.
M53 was an easy object, though, where the challenge is in seeing detail. M64 is a harder object from these skies (about magnitude 4.5); I could see some northwest-southeast elongation, but that was it. I seem to recall seeing a sort of comma shape to M64 on a previous night out, but either I've gotten rusty or this night was just bright enough to wash that particular asymmetry out.
Next up: a few doubles. First was Izar, epsilon Bootis, sometimes known as Pulcherrima, "the most beautiful." This is a tighter split than I remembered, and the magnitude differential more than I remembered, too. I could see the faint blue-white secondary at about 340 degrees position angle from about 100x and up, although it was easiest to see at about 200x. I also kept seeing a persistent bluish spot at about 220 degrees position angle, but that can't be real; I'm not sure what that was.
My second binary was Porrima, gamma Virginis. I think the separation is on the order of an arcsecond, and that is fairly in line with what I saw, with the Airy discs appearing to overlap just barely. (The human eye does not see the full width at zero intensity; it only sees, perhaps, the full width at a little less than half the maximum intensity—hence FWHM (full-width half-maximum) measurements.) Porrima used to be directly east-west, but now it is closer and distinctly northeast-to-southwest.
The third and last binary was the tightest, zeta Bootis, which is at about 0.8 arcseconds. It does not split cleanly through Opus; instead, it "bread-loafs" or "figure-eights." Even with the eye not seeing the full width of the Airy disc, these discs still clearly overlap, but with a noticeable notch where they meet.
I decided to close with a few galaxies that are pieces of cake with alt-azimuth scopes, but are a little tricky to tag with a fork-mounted SCT. First and somewhat easier is M51, which is in Canes Venatici, but just off the handle of the Big Dipper in Ursa Major. I find it by drawing an imaginary 30-60-90 triangle with eta and zeta Ursae Majoris, Alkaid (or Benetnasch) and the famous Mizar. I could see only the center and not the disc of M51, and I fancied I could see the center of NGC 5195, its companion, as well, but I wasn't sure.
Considerably more difficult to reach was M81/M82, mostly because the angle is so steep. Using a finder is pretty tricky there. Once found, however, this pair is terribly attractive and distinct even through relatively heavy light pollution. Only the center of M81 is easily seen; there is a primary halo that you can barely make out in this kind of aperture (5 inches), and then a secondary halo that extends outward that cannot be seen in the city. It is, of course, simple to see under dark skies. Apparently, there is yet more to the disc that shows up in long exposure photographs that extends beyond even that, which I have yet to see, not even in the 10-inch. M82 is one of my favorite galaxies; ostensibly, it is the favorite. Thin as a needle, with a burst of darkness and light bisecting it, it resembles a darting brush stroke in Chinese calligraphy. It amply rewards prolonged inspection; after accumulating some photons, you can make out a sort of X-shape of darkness stabbing through the stroke.
9:30 p.m. 10 June 2002 PDT (2002–06–11–0430 UT)
I know that many people like to search out new objects each time they go out, but I'm not one of them. I can spend a perfectly satisfactory evening out looking at old, familiar objects—but looking for new things, just the same. On this night, the sky was reasonable for this time of year (perhaps on the poor side of Bortle 8) and area, except for the south, where it was decidedly Bortle 9.
One of my favorite starter objects is M53, and I made a concerted effort to see if I could pick out some new detail in it. I tried a technique that I've used rather a few times to good effect, but I've never done it systematically, and I've never seen it highlighted anywhere, either. We all know about averted vision—the tactic of looking away from the object so that the more light-sensitive rods get a chance at the dim DSO. My averted vision isn't the same in all directions; the object seems easier to see if I look away from it in the 1 o'clock direction than in other directions. I suspect a similar asymmetry for most observers.
What I did, therefore, was look all around the object, so that I was using averted vision from all directions. I noticed that although M53 was easiest to see in the 1 o'clock direction, I actually saw more detail in the 4 o'clock direction, and the angle was highly specific: I saw significantly less detail at 3 o'clock or at 5 o'clock. My little impromptu sketch shows stars spilling out to the north and east from a clump that was weighted toward the southwest; meanwhile, there was a short arc, near the center, sweeping from the south, counterclockwise, to the east.
But M53 is an easy-to-see object, even from urban skies. What about M64, the Black Eye Galaxy? Conventional wisdom has it that it's pretty hard to see the dust lane from city skies with a small telescope, but it's still possible—after a fashion. At first, it's just a featureless glow in the eyepiece, but once again, by scanning around the eyepiece in this circular averted vision manner, I was able to make out that it was elongated roughly in the west-northwest to east-southeast direction (with angle about 120 degrees), and after about 20 minutes or so of trying different magnifications, I also made out an asymmetry in the brightness of the galaxy: the southwestern half was brighter than the northeastern half. I think that must be the effect of the dust lane, so that although I cannot quite see it directly, I do notice its effect on the overall texture of the galaxy.
After the concerted effort I put in on those two objects, it was much smoother dealing with Izar, epsilon Bootis. I had a much easier time making out the secondary this time; I'm not sure what caused the problem last time. I still think that it seems dimmer than it ought to, but I am nonetheless certain of it.
Another easy object to see is IC 4665, a sparse, shallow open cluster in Ophiuchus. Even at 24x, it's not quite a showstopper in the 5-inch; I think it would probably be even better at 15x in the Ranger, but I did not try that. Twenty or 30 stars in a more or less spiderweb pattern, without the benefit of great dynamic range (as opposed to M35, for example, which seems to be composed of layer upon layer of stars).
M13 is a lot of people's first choice for a northern hemisphere globular. I have to admit that I like M22 more, but the view of M13 I had tonight reminds me that M13 has much to offer as well. I can't believe I ever thought this object dim. (Well, my skies were brighter then, too.) Even with a small telescope in the city, a wealth of detail is revealed: streams of stars, a bit of north-south elongation, a certain symmetry in the streamers across that axis, a slight brightness gradient toward the south, where a clump of three or four especially bright stars lie, and even some incipient granulation. It is a thick and majestic cluster—much better in the C5+, incidentally, than the Ranger.
I followed up with the Coathanger Cluster (Collinder 399), which barely fits in the 24x, 2-degree-wide view that Opus affords with the reducer in place. I still think this is one of those few objects that looks more striking in the city than in dark skies, so it amply rewards those who put the effort of hunting it down here.
Last but not least was the Double Double, after a brief thread on it in sci.astro.amateur. Just for a lark, I tried making the pairs out at 24x, but all I could see was the elongation, and that only indistinctly. It was cleanly split at 130x with the 6 mm eyepiece; I didn't try any powers in between, but I can usually begin splitting it fairly easily at about 60x to 70x.
11:55 p.m. 15 June 2002 PDT (2002–06–16–0655 UT)
Southern California has been blessed lately with some crisp, clear nights, and this one was even on a weekend, so I decided to take distinct advantage of it. I also decided to take out the Uranometria second edition that I hadn't used in the field since just after it came in the mail. (I had, of course, browsed through it on many a cloudy night.) The skies were reasonably dark—a little darker than the previous time (zenith limiting magnitude probably about 4.6, and limiting magnitude to the south probably about 4.2 or so).
My point of departure tonight was IC 4665, which I had reported on the last time out. As I've said before, this is not a tremendously splashy open cluster, but it is easily visible to the unaided eye from dark skies. It cannot be seen that way from my backyard, but it's a cinch to find, being around a degree or so to the north-northeast of beta Ophiuchi.
From there, a nearly straight sweep east of about 10 degrees gets you to NGC 6633. One of the benefits of having an equatorially mounted scope is that you can easily sweep east and west. (Or north and south, for that matter.) NGC 6633 is an elongated, unusual-looking open cluster. It looks a little like a space shuttle landing, with its nose cone angling to the southwest. The "rear" of the cluster, however, swoops up north and then over to the northwest, almost overhanging the cluster's "front." All this in a package of 30 or 40 stars that are easily seen even here.
About three or four degrees to the east-southeast of NGC 6633 is a much different open cluster, IC 4756. This is substantially dimmer than NGC 6633, but still relatively easily seen under these conditions. It is a rounder and somewhat richer cluster, with greater depth. There is a magnitude gap between NGC 6633's first tier of stars and its second; the graduation is much smoother in the case of IC 4756. NGC 6633 is still in Ophiuchus, incidentally, but IC 4756 is across the border in Serpens Cauda.
Looping back over to IC 4665, we encounter the bright, four-degree spanning V of Melotte 186, Taurus Poniatovii (sp). It's much too big to fit into even the widest field of view on the C5+, which stretches only 2 degrees, but it also has the distinction of being a convenient pointer to Barnard's Star, the star with the highest known proper motion. It is less than a degree to the west-northwest of 66 Ophiuchi, the northernmost star in the V (on the western branch of the V). I found it surprisingly dim. I know it's pushing on 10th magnitude, but I still expected it to be somewhat brighter in the scope.
Next, I changed gears and moved over to Scorpius, and M4. I remember the first time that I looked for this globular. I had just gotten the C5+, in the middle of summer, and Scorpius was setting. I hadn't the faintest clue what "surface brightness" meant, I hadn't considered what the object's low altitude in the sky would do to its visibility, and I intepreted the globular's magnitude of 5.6 as indicating a relatively easy object to see, given the telescope.
Of course, nothing I did that night would permit me to see it. I knew I was in the right place—it's easy to locate—but I spent the better part of an hour trying to discern it, without avail. Part of it was the lack of better equipment—I had only a 25 mm SMA (Kellner) that came with the C5+, a 9 mm Kellner that came with a previous telescope, and neither of those provided the necessary contrast to make out the cluster.
But another part must surely be a matter of plain experience, and a more advantageous location, both of me here on the ground, and of M4 up in the sky. It still wasn't high tonight, but at least it was more like 20 degrees up. I was eager to try studying it again and see if I could make out the dark channel I remembered seeing last time I observed M4 under dark skies.
However, I observed no such dark channel. Instead, I saw a bright line almost perfectly north-south, which I'm sure most of you recognize as the feature that actually exists there. I'm not sure why I remembered it as a dark channel—perhaps it's the drawings I've seen in books like O'Meara's, which are negatives—bright areas are drawn in dark pencil, for example. In any case, it was provocative to be able to see the linear feature with a small scope here in the city.
Having seen M4, I naturally made my way over to M80, halfway between Antares and Graffias (beta Scorpii). You could hardly imagine two clusters more different than M4 and M80. M80 is as compact as M4 is sparse, and it takes magnification very well. I had my best view of M80 at about 100x, and it showed a fairly strong arc across the center from northwest to southeast, plus a weaker arc that extended from the southwest, and crossed over to a broad fan of stars extending to the north.
From there it was a brief trip over to the Teapot of Sagittarius, and M8. I could make out the basic shape of the nebula, with the strong concentration of brightness to the west, but otherwise, the open cluster NGC 6530, embedded within, is really the main attraction here. It would probably have received its own Messier entry if it weren't inside M8.
One of my favorite globulars—better even than M13 in Hercules, in my opinion—is M22, just to the northeast of the tiptop of the Teapot. It's broad, close enough to the Sun and Earth to be resolved, even in the city, even in a small telescope, and it has a number of fairly bright stars. These stars appeared to be more prominent toward the southern part of the cluster; on the other hand, there seemed to be a knot of brightness in the northern half, which almost detached itself from the rest of the globular. I also got the distinct impression of a notch on the eastern flank of the cluster, but I can't be certain about that.
Finally, I looked at NGC 6629, a planetary nebula about which I had no knowledge other than its location, as shown in Uranometria. It was simple to find the asterism where it was to be found, and then began the task of seeing the nebula. I could see nothing at 24x or 40x, with or without the nebula filter (just blinking it). As I gradually turned up the power with the filter in place, however, I believe it became more evident. There was certainly something there; the nebula is supposed to be about magnitude 11.6 and 16 arcseconds across, and the only other thing that is there to be seen is a magnitude 12.8 star that is about 0.8 arcminutes to the east.
I'm fairly certain, however, that I could not have seen such a dim star from here, and it was also much easier to see this blob with the filter, so that I think that I have seen NGC 6629. I estimated it to be a bit larger, perhaps 20 to 25 arcseconds across, but it was very difficult to determine. I struggled for some time to discern any kind of distinguishing mark, and finally recorded a possible brightness gradient toward the east side—very tentative, however.
9:50 p.m. 30 June 2002 PDT (2002–07–01–0450 UT)
I write a monthly—more or less—column for the Los Angeles Astronomical Society (LAAS) newsletter, the Bulletin, describing how to find and see various deep sky objects from urban, light-polluted areas. Each month, I pick one or two objects; usually, they're relatively easy to see, like the Messier open clusters, but on occasion, I pick objects that are more of a challenge to make out.
I have to make sure that the objects aren't too hard to see, and that's what I was doing this night. My first object for the August newsletter will be NGC 6819, a small, dense open cluster in Cygnus. If you draw a line directly south from delta Cygni, and directly west from gamma Cygni, NGC 6819 is very near where those lines cross—just a little to the southwest.
It is found just to the west of a trio of sixth and seventh magnitude stars. Between NGC 6819 and this threesome is a dimmer star, probably of ninth or tenth magnitude. This cluster is only a few arcminutes across, and you might think, based on that smallness and its magnitude of 7.3, that the best way to see it is to use a fairly low magnification.
But that's not so. I found my best view at about 100x; this works out to an exit pupil of just about 1.25 mm. At that power, the sky background is just dark enough to make out a small, asymmetric glimmer, the very core of NGC 6819. The asymmetry lies in a pair of streams of stars at right angles to each other. With the confusing view provided by the light pollution (the zenith limiting magnitude was about 4.7, but the sky was brighter in Cygnus—and not just because of the Milky Way—about 4.4 or so), the streams appear to cross, but I know from my views of this object from darker skies that it's more of a checkmark shape, with the angle of the checkmark opening northward.
This is a pretty little object, providing a moderate challenge from skies this bright. It is a good example of the need, even from bright sites, of letting your eyes adjust to what darkness there may be.
My other object was the Blinking Planetary, NGC 6826, which as it turns out, I've never observed before through any of my own scopes. (I have seen it through someone else's, though.) As you can tell from the nearness of their NGC indices, these two objects lie very nearly on the same north-south line, and in fact, NGC 6826 is just about due north from delta Cygni, about as far above that star as Deneb is northeast of gamma.
At magnitude 9.8, I wasn't sure what to expect, and now, after having recorded the observation, I'm still not sure what I saw. I used a narrowband filter—the Orion UltraBlock—and at high power (again, about 100x), I think I saw a couple of features: a brighter arc to the south side of the nebula, and a strange knot of intensity to the north, perhaps an arcminute or two to the north of the central star. The knot, especially, was recurrently visible, so I think there was something really there, although I didn't check to make sure it wasn't some sort of reflection effect.
Copyright (c) 2002 Brian Tung