6:45 p.m. 2 December 2000 PST (0245 3 December 2000 UTC)
Saturday night, like all first-quarter moon Saturdays, the public star party night for the Los Angeles Astronomical Society. It's held once a month, more or less, on the front lawn of the Griffith Observatory. Usually, I come just to look at other scopes, but I felt this night that it was time I paid my dues and offered views through my scope. So at about 5:30 I packed up Opus and his support crew and started off on my way toward Griffith.
What with traffic and all, it took 75 minutes to drive the 30 miles or so to the observatory, and a tense 75 minutes it was, too. Just as I had left, clouds started rolling over Santa Monica, and I was hoping against hope that I'd beat them to Griffith. The news station I was listening to kept trying to convince me it was clear over Los Angeles downtown, but it sure didn't seem that way to me. As I exited the freeway, it seemed as though the moon shone brilliantly overhead, but as I drove onto the front lawn (club members are allowed to park there to unload their scopes), a big bank of clouds was just then rolling over the grounds, obscuring everything.
Ben Kolstad informed me that it had begun clouding up about a half-hour previously. Very unfortunate. He had just received his SV80 f/6, and had only had about 20 or 30 minutes of viewing through it.
So we stood around, looking forsaken, wishing glumly that the clouds would just go away. Someone else mentioned casually that once it had clouded over just like this, and then the clouds had descended back down into the city and revealed a clear sky. Likely story. Some people began packing their scopes up.
Since we had some time to kill, we decided to look at the motor drive on the SV80, which refused to move the scope. It was difficult to see anything clearly in the dark, but we tentatively concluded the problem might be insufficient power delivered to the drive. (Hence Ben's question about the current draw on the drive.) That was of course not possible to fix right then and there, but for the moment, it was a reasonable proposition to use the RA knob to keep objects in view. Not that there was much to see. Every now and then the moon would make a dim, fuzzy appearance, and on those occasions it was surprising how much detail could be seen on the surface (the clouds worked as a kind of neutral density filter), but that was about it.
Sucker holes were a matter of course. Having read the news notes part of Sky and Telescope, it occurred to me that sucker holes were an indication that the cloud layer was low and relatively thin. I related it to the "graininess" method of determining distances to galaxies. Sucker holes are a sort of coarse granularity; if the cloud bank were much higher, the holes would be smaller, and if it were thicker, they would be absent.
Then, suddenly, around 7:15, things began looking up. A bright star was visible in the west, though I couldn't make out, in isolation, which one it was. Then Ben noted, higher in the northwest, a set of stars that seemed to be Deneb, along with gamma and epsilon Cygni. He proved to be absolutely right, and that made the western star Altair. Then Vega showed. We turned to the east, and there, poking through the haze, were the gauzy apparitions of Jupiter and Saturn. It looked like another sucker hole, but this one was huge, and what's more, the hills were beginning to come into view. Maybe the clouds were sinking into the city.
The clouds, it turned out, left as suddenly as they had come. Within 15 minutes, Ben and I had gotten a look at Jupiter through a TV 85 and seen the GRS just about at CM transit. I figured I had better get ol' Opus set up before it clouded up again.
First light that evening was Jupiter. Even the first 10 seconds, before the scope had gotten a chance to seriously cool down (although it had stayed in the poorly insulated front seat of my car), revealed a night of uncommonly steady seeing. Usually, at this first stage, only three belts, the SEB, NEB, and NTB, are visible, and blurry to boot. But now they were sharp and clear, with some texture visible in them and in the high temperate zones as well.
It would only get better on the seeing front. I tried to broaden the horizons a bit by pointing the scope to NGC 1647 (which has now made the Binocular Highlight section of Sky and Telescope twice in the last couple of years), but it was clear that 5 inches weren't enough to make it a highlight under these skies—at least, not to the public that was milling through. I turned it back over to Saturn, and I have to say, it was very gratifying to hear the oohs and aahs.
Obviously, I took some time to observe the planets myself. By 8:00, the seeing was rock steady from time to time. Cassini was nice, dark, and sharp, and even the Encke minimum was unmistakable. At first glance, it looked much as it had on previous occasions: a broad, shallow dimming that started about halfway out on the A ring, and extended about to the 5/6 point, just where the Encke Division is (but is of course invisible in this scope). But normally, seeing makes the minimum seem like the thin line that leads some observers to think they are seeing the Division, whereas on this night, the minimum had obvious width, even at 167x. A real astonishing sight.
Oh, that reminds me—the 167x, that came from a 15 mm Plossl Barlowed. I was getting sharper and more detailed views from that unhallowed combination than I had gotten in some time from the 6 mm Radian. Since the Radian is usually 50 percent sharper than the Plossl/Barlow (in a very subjective sense, of course), I wished I had brought it. I had to keep reminding myself that it was a public party, and things can happen at public parties. But it was still mildly irritating that I didn't have it with me.
Jupiter was improved also, by 8:30. Now the GRS was rotating around to the leading edge, and beginning to get harder to see, but even then the seeing supported some incredible detail. The center of the GRS, as well as the southern third, was darker than the rest of it, making a chess pawn shape inside the oval of the GRS. I saw only a couple of tiny festoons off of the NEB, but plenty of barges on the NTB, and there was also a hint of two small ovals in the NEB, where I had never seen any before. I'd say it was about the best night I had ever witnessed, with regard to atmospheric steadiness. I even discerned, just possibly, some fleeting surface detail on Ganymede itself! It looked like a very broad (i.e., obtuse) two-limbed dark patch, toward the leading (celestial west) edge of Ganymede. Can anyone tell me what would have been visible at that time?
Over and over it was remarked, through my scope and others, that there was more detail on Jupiter than could easily be recorded. In a way, it was almost too bad it was a public star party night, and we couldn't be left to our own scopes, to take copious notes. On the other hand, though, what better way to lure a few unsuspecting passersby into the best hobby in the world?
Copyright (c) 2000 Brian Tung