My Observing Log: March/April 1999

6:00 p.m. 2 March 1999 PST (0200 2 March 1999 UTC)

Just a short peek today. I caught Mercury high and bright against the twilight sky, so I brought the C5+ out for a fast peek. As I suspected, no detail was visible at all—I could barely make out that it was not quite round (because of the phase). No hope of making out the phase. Not surprising since the scope had no time at all to cool down.

11:30 p.m. 5 March 1999 PST (0730 6 March 1999 UTC)

Mars was the target tonight, with the just-past-full moon still glaring and all the other planets down early (though we did have some fun watching first Venus, then Jupiter and Saturn, and finally Mercury make their way out as the sky darkened). I looked out at about 11:00 and found the sky reasonably clear and Mars hanging lowish in the south-east about 10 degrees down from the moon. I set up the scope and took a quick peek through, but Mars's image was still floating around as the tube needed cooling down.

A half an hour passed by as I waited indoors. When I went out, unfortunately, the clouds had closed in and Mars was only intermittently visible. The central meridian was about 330 degrees, although I did not check it beforehand—I didn't want any prior knowledge to influence what I saw. I could make out three dark patches, which later turned out to be Mare Acidalium and Mare Erythraeum as with the last time, and also the surprisingly dark Sinus Sabaeus. I could not make out the hook, called Sinus Meridiani. Neither, surprisingly, did I see Syrtis Major, probably because I was not specifically looking for it. It might also have been too close to the edge and the disc was ever so slightly gibbous (instead of completely full), so that might have affected things further.

Battling the clouds was a losing matter after only 10 or 15 minutes, and I decided to pack it in. A little disappointing, but I did get to add one more surface feature to my observing belt.

1:00 a.m. 24 March 1999 PST (0900 24 March 1999 UTC)

[Posted to sci.astro.amateur.]

One of the reasons I bought my C5+ was for its portability, and that aspect of it has borne me well. I routinely take it out for 15 or 30 minute quick peeks and don't count the overhead of set-up and tear-down as more than 5 percent or so.

There are drawbacks to using the C5+ for so short a period, of course. One is that the scope doesn't really get a chance to cool down for most if not all of the session. Many times I attributed it to atmospheric disturbance—bad seeing, in other words.

Then a couple of weeks ago I decided to leave the C5+ out for a couple of hours to cool down properly. (I figure it doesn't take nearly that long to cool down enough, but we had company over and it wouldn't have looked good to stand up halfway through our evening and say, "Sorry, but I think the thermals have settled down and I have an observation of Mars to run off to.")

The result? The image of Mars was remarkably steady. The Airy disc and rings of Spica were nice and steady. Unfortunately, the view was also misty, as a fine layer of dew had settled on the corrector plate. Curses, foiled by the so-called dry Los Angeles air. Ah well, I said to myself, mentally making a note to put on my corrugated cardboard dew cap the next time, and I put the scope away.

Last night was the next time. I set the scope up at about 6:30 local (Pacific) time and put the dew cap on. I took a look at Venus and Saturn, wasn't quite satisfied and used Betelgeuse to check the collimation. Disc a bit out to 5 o'clock, so I took out my Swiss army knife to adjust the secondary.

Those of you ahead of me can raise their hands. Of course I found that I couldn't reach the secondary with the dew cap in place. OK, took it off and mucked with the screws until I had a nice, tight, and centered disc. I put the dew cap back on and checked out the Trap at 83x and 140x. I had a possible sighting of E but was still seeking F when my son (supposedly asleep but audible on the intercom) started calling desperately for daddy. Observation time was put on hold for the time being.

One thing led to another and it wasn't until 10:20 or so that I got a chance to look up again. At that point Mars was up at about 15 or 20 degrees altitude (approximately—I didn't figure it out) and was swimming, and this time I was pretty certain it was low altitude seeing. Tried again at 11:00 and it was a little better, but not much.

Finally, at 1:00, with everyone else asleep, I slipped out onto the roof deck and tried again. The time was thus about 0700 24 Mar 1999 UTC, and the central meridian was, I think, about 160 degrees. To my dismay I clearly saw two white patches at the edge of the disc, one on either side of celestial north. Quick: which way does Mars incline? Through the star diagonal the one clockwise of north in the eyepiece was the real polar cap; the other was an impostor. But what was it? Chryse? A cloud patch? I decided to withhold judgment and try again in a bit. After all, it's not exactly a feature-filled view of Mars.

In the meantime, I thought I'd point the scope toward a few old chestnuts that I had missed last summer when I bought the C5+. First on my list was gamma Virginis, aka Porrima. It's a nice double, just about east-west, each element at magnitude about 3.5. I tried first at 140x; it seemed good there, with two distinct Airy discs, but a bit tight for my taste. Slipping in the Barlow for 280x yielded lots of separation. The Cambridge Star Atlas lists the position angle as about 298 degrees, implying the primary is the east star of the pair; to me, the eastern star seemed just a tad, perhaps 5 percent, dimmer. Then again, it could just be my eyes playing a trick on me.

I turned my head toward the east. That bright star—I thought, that couldn't be Vega already, could it? Sure enough, it was. That inspired a peek at the Double Double. I already had the 9 mm ortho in there, so I left it in there, rather than pull out the 15 mm Plossl. Both pairs were nice and cozy and well split, like a foursome of moons with halos on. To me, they seemed wider than gamma Virginis, but the CSA lists the separations on the Double Double at 2.3 and 2.6 seconds, and that of Porrima at 3.0 seconds. Then again, Porrima is fast closing and that separation is undoubtedly from a few years back. Ian Ridpath's Monthly Sky Charts contains a prediction that the separation in 1999 would be around 1.5 seconds; anyone care to check that with their own observations?

Another object that I had missed the first summer was M13, the great globular cluster in Hercules. For such a mighty hero, Hercules doesn't contain very bright stars, and not finding M13 last summer was more a matter of lack of perseverence (and being fascinated with the Dumbbell and the Ring) than anything else. I still have a bit of trouble in these light-polluted skies finding the Keystone quickly.

My heuristic this time was to look halfway between Arcturus and Vega; this put me at the southwestern star of the Keystone. I nudged the scope northward toward the northwestern corner, but light pollution was such that M13 wasn't visible even in the finder. I guessed, sliding the view about 2/3 of the way northward and looked into the eyepiece.

I must have nudged the focuser as well; a field star was a bit out of focus. I adjusted that and had just about noticed a faint fuzziness when *bonk* I pushed the scope just enough to lose the view. I had forgotten to lock down the RA clamp.

I muttered softly and found my place again. This time the view was perfectly sharp. No granulation or resolution—the background sky was too bright for that—but a nice mound of powdered sugar describes the view quite accurately. Beautiful! I put that on my list of things to return to again and again—it was much better than Cats—and decided at this point to return to Mars.

By this time it was 2:00 (1000 UTC). The view this time was even steadier, although sporadically, and for a half a minute or so, Mars would swim in a cell of turbulence. The polar cap stood out in stark contrast, and a dark patch near the south pole, angling up gently toward the celestial eastern (trailing) equatorial region was visible. (This turned out later to be a combination of Mare Sirenum and Mare Cimmerium.) A dark hook also appeared on the trailing edge, near the equator; this was Syrtis Major, experiencing Martian dawn.

I'll have to admit I may have gotten these majorly screwed up; this is my first opposition and I don't know all the markings yet. If I have my math right, the CM at the time should have been around 175 degrees. Is that right?

And that white patch? Still there, suggesting it wasn't Chryse but instead a patch of clouds. It was even a bit larger than the polar cap, or appeared so in my scope. I wanted to watch even longer, but it was getting cold and late, and Mars rotates slowly, even slower than I do. I packed it in for the night and went in to warm up and go to bed.

6:00 p.m. 24 March 1999 PST (0200 25 March 1999 UTC)

In contrast, an exceedingly short session tonight. Inspired by a recent thread on sci.astro.amateur about how much magnification is required to split Castor, I checked it out for myself. I used my three eyepieces yielding 50x, 83x, and 140x, respectively.

At 140x, it was obvious. A clean split with a distinctly dimmer secondary at about 75 degrees from the primary. At 83x, it was still pretty clear. At 50x, it was a bit muddy. Definitely elongated, and it looked a bit like a filled in figure-8. It's conceivable that if I had let it cool down, it would have been clearer, but I didn't wait to find out.

One further bonus is that I think I finally did make out the elusive F component of the Trap. It was further out from C than I thought it would be, although still blindingly close. I'd say it was perhaps one-half to two-thirds as far from C as E is from A. In the fading twilight, it was an exceedingly faint dot.

7:00 p.m. 27 March 1999 PST (0300 28 March 1999 UTC)

Did some more double and multiple star observing tonight. I started with a popular favorite that I hadn't seen before, beta Monocerotis. This is a nice triple, with the B and C tight and about four o'clock (in the star diagonal) from A. Very nice. Distinct, though seeing-fuzzed, at 83x.

Sometimes I like to look first and check the position angle later, to make sure I really did see it and didn't delude myself into it. That's what I did with Rigel. At 83x, this is an amazing pairing. The fiery blue-white brightness of Rigel, and then this tiny little seventh-magnitude dot at about 5:00—no, about 5:20, which works to about 160 degrees. Lo and behold, that's what the position angle is. Exciting!

I took a break from these doubles to take in NGC 1647, a nice rich open cluster in Taurus that could just have easily been part of Messier's catalogue. It's at RA 71.5 degrees, Dec 19.1 degrees. Here's a finder chart for it. Field of view is about 6 degrees wide, north is up, east is left, and stars are shown to about magnitude 9. Aldebaran is the bright star to the lower right. You should check it out, this is really a nice cluster!

I then returned to the Trapezium. Luckily for me, there was a 10-minute period of very good seeing. I'd have rated the rest of the night as perhaps a 5 or a 6, but for those 10 minutes, the atmosphere was very steady, a 9 I'd call it. And the effect on my view of the Trap at 83x was electrifying. I'd never seen E so steady in my life, clearly evident even under mag 4 skies with direct vision. And I definitely saw F. It was there about 50 percent of the time with averted vision, and even about 10 or 20 percent of the time with direct vision. Awesome!

Here's a finder chart for these "small" components of the Trapezium. It's at RA 83.819 degrees, Dec –5.387 degrees. Field of view is about 0.10 degrees wide, north is up, east is left. The four bright stars are, from right to left, A, B, C, and D; then the two dimmer stars are, from right to left again, E and F.

I wanted to do some lunar observing, but the seeing worsened rapidly and the clouds also started moving in, so I gave up for the time being.

Copyright (c) 1999 Brian Tung