12:10 a.m. 23 April 2005 PDT (2005–04–23–0710 UT)
I decided to go out for a very quick look tonight, and owing to some unexpectedly good seeing, I ended up staying for the better part of an hour.
I hadn't yet had a look at Jupiter this entire apparition, so I was eager to train Opus in that direction. The first look was pretty promising, so I decided to tweak the collimation. Opus lives in the garage most of the time, so it comes out pretty much at ambient, here in moderately climed Santa Monica. Just about any movement in the image is due to seeing, therefore, so since the image looked steady in the eyepiece, I had some confidence that it was worthwhile tuning the alignment.
That proved to be the case. A couple of tiny turns on the Philips screws on the secondary cover, and the image quality was subtly but noticeably improved. Before returning to Jupiter, I tried a few double stars. First was epsilon Bootis, Izar aka Pulcherrima. I knocked the focus knob off, and it took a bit to recover it, but once I did, I was able to make out the little blue secondary, sitting just outside the first diffraction ring of the primary—almost like a little Albireo.
On a night of even better seeing, once, I trained the Wocket (my 70 mm Tele Vue Ranger) on zeta Bootis and was able to "breadloaf" it. It wasn't quite that good tonight, but it was close. The larger aperture of the C5+ made the split somewhat easier even though the seeing wasn't as good.
How good was it? It was sub-arcsecond about half the time, in my estimation, and even at its worst it was no more than 2 arcseconds or so, and fairly slow, moving perhaps a few arcseconds per second. Good enough to try Porrima, gamma Virginis. I knew that in recent years it had gotten too close to split or even figure-eight; the best I could hope for was to see an elongation and try to determine its position angle. It took quite a bit of waiting and watching, but after maybe 10 or 15 minutes I decided on a position angle of 320 to 330 degrees.
I was going to walk in and check on-line, but then I remembered that I had earlier answered this question for Pete Lawrence, and it seems that we had both picked the wrong end of the elongation as the primary, and arrived at an answer 180 degrees off. Since the actual position angle is somewhere in the vicinity of 150 to 160 degrees, it looks like I wasn't too far off. That sounds promising, but I realize that I had seen the answer—even if a few weeks before—and I could easily have been influenced by that, subconsciously. I'll have to chalk it up as a probable, but not a confirmed, observation.
Porrima is very close to Jupiter these days, so back to that worthy. The image was quite steady. The SEB and NEB seem more subdued in color than in past years, with the NEB very slightly redder than the SEB. I was struck by the paucity of festoons off the equatorial edge of the NEB; I made out some smallish beginnings of festoons at about the central meridian and perhaps another 30 or 40 degrees toward the following edge. There was no distinct NTB; what there was seemed to fade off pretty gradually toward the north polar region. In contrast, there was a sharp edge to the STB, especially in the following half of the disc, which faded in the preceding half almost to nothing by the preceding edge. There also seemed, in the following half, to be a bifurcation of the STB.
Copyright (c) 2005 Brian Tung