My Observing Log: July/August 1998

10:30 p.m. 25 July 1998 PDT (0530 26 July 1998 UTC)

I received my C5+ on Friday, but the westside of L.A. was then blanketed by a thick layer of clouds, and I spent my time adjusting my finderscope. It's not great, but serviceable. There is a stop in it, which has a central hole about 18 mm in diameter, but it is part of the way in from the 30 mm objective. I haven't done the math to see how far down the objective is effectively stopped to.

Today, though, the clouds lifted sufficiently to bring it out for first light. Some friends were over, so I limited the brief session to some old standbys—Albireo, Mizar/Alcor, epsilon Lyrae, and the blinking red eye of Antares (yes, the seeing was pretty bad). My friends were uniformly awed by what they could see, and wanted me to point out where in the sky these things were.


"Well, do you see that triangle of stars (the Summer Triangle)?"


"OK, from that dimmer one over there (Deneb), draw a line to a point halfway between the other two. On the way there, you'll see two even dimmer stars."



"Do you see the Big Dipper?"

"Is it those three bright stars (epsilon, zeta, and eta Ursae Majoris, the three handle stars)?"

"Well, yes, that's the handle. Do you see the box of the dipper beneath those?"


I didn't even bother with epsilon Lyrae (which was—just barely—visible directly overhead). I showed them the view at 50x, which is not quite enough to show the Double Double, and then the view at 140x. They had an easier time splitting epsilon1 than epsilon2. I did mention Vega, though, and showed what that looked like through the scope.

My point is not to demean the vision of my friends (even if they're reading this, though I doubt that), but just that it was surprising how much more you can see when you know what to look for. Probably even a year or two of experience can't hurt, either. I mean, they were pretty obvious to me. :)

Later, the clouds returned briefly so Jupiter wasn't visible before they had to leave. At about midnight the sky cleared up enough to expose Jupiter, so I brought that worthy into view, popping in a Barlow and my 9 mm Kellner (from my old scope). Very nice! Both equatorial bands were clear, plus one more on the southern half. I was again impressed by how much limb darkening obscures details near the edge of the disc, although it always appears to me that the disc remains bright, and just the details wash out. Perhaps some filters would help? I can't wait to check it out when it's up a bit higher in the sky, and when Saturn follows.

As far as the scope itself goes: Alignment was easy. Sighted it with Polaris—I found this easier without the finder than with it. This took about 20 or 30 seconds, and was good enough that I could leave the scope tracking for a half-hour or so, and still find my target centered in a one-degree field. I'd estimate the wander was on the order of 5 arc minutes, at most.

The right ascension clamp doesn't hold as tight as the declination one: is this typical, or should I worry about it? I did get it mail order, so it's a moderate hassle to return it, and I'm planning on doing mostly visual work. I estimate the piggyback bracket will hold about 10 pounds without counterweighting before the scope slips in RA. Not much, but probably sufficient.

The seeing was bad enough that I had trouble doing a proper star test, or maybe I need more experience? The image at 140x was swimming around quite a bit. Diffraction rings were visible but unsteady.

11:00 p.m. 27 July 1998 PDT (0600 28 July 1998 UTC)

Right ascension clamp problem fixed. Here was the problem: the clamp is tightened by means of a threaded bolt, and the bolt has a 90-degree handle. The handle runs into the base of the mount, and so only has roughly 180 degrees of travel. At the extreme end of that travel, it still felt as though the clamp could be tighter.

The solution: There are two small holes where the handle meets the threaded bolt, one on either side. Careful inspection reveals that these holes are hexagonal. It turns out that these are small screws that one can pull out using a small hex wrench. Loosening these just a little is sufficient to allow you to remove the handle.

This exposes the bolt, which has a slot for a flathead screwdriver. You can tighten or loosen this as necessary; obviously, I tightened it. Do not overtighten, as this will simply warp the washer that is evidently inside the clamp. Replacing the handle is then a simple matter of putting it back and tightening the little hex screws.

I began the night with another attempt at a star test. Seeing was still pretty bad, but sufficiently improved over last Saturday to allow me to compare the images inside and outside of focus. Both were clearly round and to my mildly experienced eyes identical. Both had strong secondary diffraction rings, which are apparently expected for an obstructed telescope. The in-focus image was still swimming around too much for me to determine much of anything.

I set the right ascension circle and decided to try using the setting circles to locate objects. I calibrated using Vega, which was nearly overhead. The C5+ has two sets of numbered rings for the right ascension circle; the inner one is for the northern hemisphere, and the outer one for the southern hemisphere.

I first tried to locate the Dumbbell Nebula, M27. Using the setting circles got me to within about a degree—that put it in the finder, but not the main scope at 50x (which gives about a one-degree field of view). I knew that M27 was located directly above (that is, southeast (!)) the middle of a fairly bright W, so I started from the bright middle point of the W. (Here's a finderscope view (6.5 degree FOV) of where M27 is. North is up, east is left. Stars shown to about magnitude 9. Coordinates are RA 299.9, Dec 22.7. I hate sexagesimal notation. <grin>)

My short hop for finding M27 from that bright star is to use a flat triangle of stars. Unfortunately, there are two of them—one that's northwest of the start point, and one that's southeast of it and actually contains M27. I initially confused one for the other (and in the process bypassed M27); eventually, I realized my mistake and then had no problem spotting the nebula. It was visible, but somewhat disappointingly dim, given its brightness (about mag 7.4), even with the narrowpass filter.

My next target was the Ring Nebula, M57. This time, I knew the approximate error that I had gotten when attempting to find M27, so I tried to take that into account. This time, the setting circles got me within about a half-degree of M57, so it was sitting right at the very edge of my main field of view, toward the southwest. A few turns of the fine controls were sufficient to bring it back to the middle of the field. (Here's a finderscope view (6.5 degree FOV) of where M57 is. Stars shown to about magnitude 9. Again, north is up, east is left. Coordinates are RA 283.4, Dec 33.0.)

Well, the Ring Nebula was as impressive as the Dumbbell was disappointing! M57, at mag 8.8, is about a magnitude and a half dimmer than M27, but that's an integrated magnitude, and M57 covers an area only a few percent that of M27, meaning that its light is concentrated over a relatively small area. The donut shape of it was clearly visible at 50x. On the downside, the narrowpass filter did not increase contrast noticeably. Higher magnification only made it harder to see.

Jupiter rose to about 30 degrees altitude at the end of my session, but was swimming in incredibly bad seeing; even the main equatorial bands were barely visible. I gave up the ghost after a while.

1:00 a.m. 29 July 1998 PDT (0800 29 July 1998 UTC)

Additional stuff to see this time: M31. I had trouble finding this with the setting circles; I relied instead on a star hop, starting from alpha Andromedae, one of the stars in the Great Square of Pegasus. Most of it was conducted in the finder, until I found a fuzzy dot. (Here's a finderscope view (6.5 degree FOV) of where M31 is. North is up, east is left. Stars shown to about magnitude 9. Coordinates are RA 10.7, Dec 41.3 (center).)

Of course it wasn't as impressive as it is in those photographs, but I was still somewhat surprised that something that was visible by unaided eye (just barely) was so faint in the scope. The center of the galaxy was quite distinct, but it only filled about one degree of field, instead of the three I expected. I don't know if I saw any of the satellite galaxies.

I was just barely able to catch its position angle at about NE. (I couldn't see any finer than that.) I believe I've got that roughly right, though I haven't checked with any of my reference sources yet.

Another target, more suitable this particular night because I started so late, was Saturn. By that time, dew had covered much of my corrector plate, and everything was coated in a light, moist halo. Very romantic, but at the same time not inducive at all to clear observation.

Even so, and even with seeing that made Saturn vibrate and swim even at about 40 degrees altitude, it was an amazing sight. The 25 mm eyepiece allowed me to see the bands, and with the 9 mm eyepiece I was just able to see the Cassini division. At this magnification and time I wasn't able to see it as a black band running all around the rings, but instead as an almost detachment at either extremity. This makes sense, since at this point we see the division as a lane running away from us, and this gives us maximum contrast.

Unfortunately, with the fogged optics, I wasn't able to use the Barlow with the 9 mm. With the 25 mm, yes, but of course I wasn't able to see anymore with that than I was with the 9 mm alone. So that will have to wait for some other time, when I've bought some accessories to deal with the dew. I didn't think that in the warm weather of Los Angeles I'd ever have this severe a problem with dew.

Finally, of course, was Jupiter. This was amazing. My quest for the Great Red Spot remains unfruitful, but I was actually able to see the shadow of Io on the large disc of Jupiter! Three of the moons strung themselves out from the equator of Jupiter, and Io was clearly visible, I think in the southern equatorial band. The shadow was tiny, only a few percent of the diameter of Jupiter, but that's what's to be expected.

I know that at some point I'm going to lose the initial infatuation with the scope, and use it less—in fact, I'm probably going to take a break tonight to get some more sleep—but in the meantime, the stuff I'm seeing each night is incredible.

12:30 a.m. 30 July 1998 PDT (0730 30 July 1998 UTC)

Only a short observing session tonight (I just couldn't stay away!). The clouds were moving in, so I made sure I got a good look at Jupiter. The seeing was somewhat better than the previous night, and the improved contrast allowed me to see more of the belts. Some detail was visible in the north equatorial belt: close examination revealed three spikes extending equatorward from the edge of the belt.

I was also able to get my first view of the Great Red Spot (GRS). I wasn't certain at the time, but I later verified that it was in the spot that I saw it, so I'm now sure I did see it. As promised, it is now more of a Great Red Hollow, its red color now paled to become lighter than the rest of the southern equatorial belt. It nestled itself toward the leading end of the belt (that is, the side about to rotate away from view toward the dark side of the planet); I believe I caught it somewhat after [later note: wrong, that would be somewhat before] it crossed the center meridian. A stunning view!

I saw something else that troubled me a little: Jupiter had a red fringe on the southern pole, and a blue fringe on the northern pole. I knew this couldn't be a real feature on Jupiter, and had to be a consequence of either the atmospheric conditions here or the optics. After consulting with another C5+ owner by e-mail, it appears that there are two likely explanations.

One is that Jupiter was low enough in the sky that the atmosphere refracted the light rays and caused them to spray out as through a prism. Over most of the disc of Jupiter, these rays would recombine to form the usual cream color (albeit with a reduction in contrast), but at the ends, only the blue light from one pole would appear outside that pole, and only the red light from the other pole would appear outside that pole.

The problem is that Jupiter was, at the time I saw it, already reasonably high in the sky, about 45 degrees altitude. The other explanation, as I predicted, was collimation. If the optics aren't perfectly lined up, the light rays can go "crooked" through the mirrors and lenses, and end up refracting for that reason, with the same effect. The funny thing is that I didn't catch any collimation errors when I first checked out the scope, but on the other hand, I didn't expect to see any. Maybe if I check again this afternoon with the intent of hunting down any such errors, I might be able to fix it. The C5+ only allows one to adjust the secondary in the middle of the corrector plate, so my options here are limited. We'll see!

Oh yes, one more thing. Based on the exit pupil size, it appears that the effective aperture of the finder is in the range of 22 mm to 25 mm. So the stop reduces the available light by about 40 percent. That is substantial, but on the other hand, I haven't noticed any significant problems locating anything with the finder so far. With the setting circles, yes, but I suspect that's because I haven't spent more than about half a minute setting it up. :)

[Note: Well, it appears that collimation was at least part of the problem. I decided to get extremely anal (it is, after all, difficult to be kind of anal) about the collimation, and there was no doubt that it helped. But it also appears that part of the problem was the atmosphere, because the effect is certainly stronger when Jupiter is low in the sky.]

11:30 p.m. 4 August 1998 PDT (0630 5 August 1998 UTC)

Well, no log entries for the last couple of days because it's been cloudy here. But it was clear tonight and I did get a bit of observing done. I started with the moon, hoping to take a look at Plato, to see if I could catch any of the craterlets inside. I didn't realize it was so close to the edge! I suppose I might have been able to get them if I had tried a couple of days earlier (the terminator had passed them a while ago, I'd say), and the seeing was any better. It was terrible—even with the moon high up in the sky at about 60 degrees altitude, its image swam and swam, obscuring any details smaller than a few arcseconds.

I also tried Jupiter. I had to wait as it rose over a (non-heat-generating) wall next to where my C5+ was set up, but there too the image wavered and shimmered. I could get the moons to focus quite clearly (and there were even discs for Ganymede and Callisto), but I could only see four bands on Jupiter. Don't know if the GRS was supposed to be out or not, but I certainly didn't see it.

Tried the star test again, and again I noticed that the rings seem steady inside of focus, but shimmer in an almost biscuity way outside of focus. [I later talked to a guy at Pocono Optics, and he told me that that's quite typical. What happens is that outside of focus, you are focusing on the atmosphere, so the seeing is quite evident there. Inside of focus, you are really focusing "past infinity"—no light rays from any single object converge—so you see nothing clearly, and the seeing doesn't interfere with the diffraction pattern.]

[Further note: I also bit the bullet and purchased a Televue 15 mm Plossl from Pocono. I got the telescope itself from Adorama—in fact, Pocono told me to get it from them since the price was so good—but I'm bound and determined to get everything else from someone who actually knows anything about astronomy. The C5+ came with a 25 mm SMA (that's a modified Kellner that Celestron designed), and my old Orion 4.5" had 25 mm and 9 mm Kellners (I'm continuing to use the 9 mm). I might replace those (I already don't use the 25 mm Kellner), but in the meantime, I thought it would be nice to have a good quality eyepiece I'll use forever.]

12:30 a.m. 11 August 1998 PDT (0730 11 August 1998 UTC)

This is really two observing reports in one, because the first one is just a prelude to the second. Last night, while I was up on the roof deck, observing the Ring Nebula (M57, see above), my wife Debby came up to see what I was doing. I explained that I was looking at a "faint fuzzy" (it's a technical term, you know), and she asked to take a look. Of course I didn't move it to something brighter.

Well, you know what happened next; she looked through the eyepiece and couldn't see anything. To make it a bit more entertaining, I put Jupiter in the view.

To see why this wasn't the best idea, you have to understand that there are two observing spots on my roof deck: one is an obstructed area with a table, which I will henceforth call The Table, and the other is unobstructed but on top of our bedroom, and that spot I will henceforth call The Roost. Just for the sake of brevity.

I was at the time seated at The Table, which as you can imagine is quite a bit more comfortable than The Roost. Unfortunately, Jupiter was at that time rising over The Water Heater, and was the victim of some bad induced seeing. So Debby was rather unimpressed with that display too.

But I had the moon, fortunately. The solace of all newbies. Debby commented that she wished they all showed up like that. I decided not to point out that Jupiter is some 2000 times farther away and all.

I got to thinking, though, because I was hoping to see something on Jupiter, so I moved the whole kit and caboodle (which is terribly easy with the C5+) over to The Roost. The view of the moon was much steadier from there (it and Jupiter were about five degrees apart, and would pass by each other during the day), and Jupiter was better too. Debby would confirm this (although I had to bring her out again—she had ventured back into the house in disappointment).

Which brings us to tonight. I was about to go to bed (in the interest of harmony, I figured it wasn't a good idea to go every night), when Debby asked me if I was going up (to the roof). I said I wasn't planning on it, to which she rejoined, why not? Well, a very good question, that. So I ended up going.

Am I glad. The seeing tonight was, I'd say, excellent, easily the best since I got the scope. Jupiter was magnificent, with the Great Red Spot showing up nicely and passing meridian about 1:30. (I didn't get to see it cross the meridian, though—the clouds obscured it just before that point.) The GRS even showed some detail: a distinctly darker mottling on its southern side.

The NEB (North Equatorial Belt) was clear and contrasty and a rich robust brown (I feel like I'm describing coffee), with a southward extension just leading the GRS. The SEB was dimmer but nearly twice as wide, and cupped the GRS about halfway through. On either side of these two main belts were visible lesser belts, especially in the northern hemisphere, where I saw a thin gray belt with little notches on the north side.

Best of all I got to see Europa's shadow transit Jupiter. Because Jupiter is still nominally an evening planet (it's between western quadrature and opposition), the shadow should lead the moon itself, but I couldn't quite make out the moon. The moon actually trails its shadow by over an hour and a half, more than I would have suspected.

I also made a visit to M57 and M27, the Dumbbell Nebula, my two standbys. M57 showed up nicely without the narrowband filter, but with it, it became a nice green ring. Spectacular! Again, M27 was dimly visible without the filter, but with it took on what I imagined was its dumbbell shape. I suppose I could be seeing something that isn't quite there for me to see, but I really thought I saw it. And quite bright with the filter, too!

I finished with a return to epsilon Lyrae, the famous Double Double. Now, I had seen this through the C5+ at 50x and at 140x, but never with the barlow in at 280x. I'd used the barlow with Jupiter at 280x, and I was to say the least underwhelmed. Total contrast loss. But still, the C5+ should perform extra well at splitting close binaries with the size of the secondary. Strangely, I'd used the barlow with my old Newtonian, but not here.

The result was, to put it mildly, quite stunning. Each of the quartet appeared very distinctly with a clear Airy disc, and a sizable separation between each pair. I got the impression that Dawes limit of 0.9 seconds, about 40 percent of the separation for each pair, would have presented little if any problem for the C5+. I've got to look for more of these to split. Just a bunch of fun.

I know I'm going back to the same old things over and over, but I like the feeling of getting to know them well. Besides, I've got plenty of time to add more objects to my repertoire. All in all, it was a wonderful night of observing. Now, if I could just remember to invest in a little insect repellant…<scratch scratch>

1:30 a.m. 19 August 1998 PDT (0830 19 August 1998 UTC)

To those couple of you who check this regularly: I haven't been observing because—well, remember that old adage about new telescopes bringing clouds? Let's just say that it applies just as well to new accessories too. To any of you observing from Los Angeles, I'd like to apologize for purchasing a TeleVue Plossl. :/

But finally, the clouds broke, and I got in a decent though late night of observing. I slid in the Plossl, a 15 mm, and craned the C5+ toward Jupiter. I think the GRS had been visible earlier in the evening, but by the time I got to looking at Jupiter, it had turned around to the other side. It doesn't take long, after all. Contrast was reasonable. There was a sequence of festoons on the equator side of the NEB; not much else was visible (but I'm far from experienced at this, I'll admit).

My next target was Saturn, with the Barlow (an Orion model) and the Plossl. Pretty good: I could see the shadow of the planet on the rings, which will get harder as the months wear on (and Saturn approaches opposition), and I thought I could see the Cassini division. I noticed that the image was just a tad fuzzy, and I played the focusing knob ever so slightly (probably less than five degrees rotation) to see if I could improve it.

Wow, could I ever! The image was incredibly sensitive to focus. This tiny change (remember it takes some 40 turns to go from close focus to infinity on the C5+, and this was about one hundredth of a turn) enabled me to see so much more. The Cassini division was now clearly visible most of the way around the planet, and I could see the intimations of the inner crepe (or C) ring. Using football injury terminology, I'd say the C ring was questionable (that's 50 percent, for you non-sports fans).

I also tried the eyepiece on some deep-sky stuff. Old targets—M27 and M57. The Ring Nebula was beautiful in it, though I had trouble finding it in the Plossl; I had to switch it for my 25 mm SMA, center it, and then put back the Plossl. They're not parfocal, so finding focus again was non-trivial. But once I found it, it was very nice, again with a noticeable dark spot in the middle of the donut. The filter didn't help noticeably on this one.

The Dumbbell was nice again, and in contrast with M57, was helped by the filter. It's amazing to me each time how, even when you think you've got your night vision, the image of this nebula just gets brighter and more detailed by the second. By the end of one minute, I could see tons more detail than I could when I first got it into view, and just as much more after five minutes than I could after one. It really teaches you to be patient, that's for sure.

I lastly slid over to M31, yet another old target. I'll come right out and say it—I'm not one of those observers that like to look at new things all the time; I'd rather see the same old hoary targets and get nice and comfortable and familiar with them, and then move on to something else, pretty much one or two at a time. And the Andromeda Galaxy didn't disappoint. You may recall me describing it as only a dim fuzzy patch. Well, this time, it showed up as a bright nucleus and a definitely visible outer portion, aligned roughly NE-SW, as I also mentioned before. I think I might have been able to see a dust lane (doubtful = 25 percent), but it was getting sleepy and I was getting late. Or something like that.

I think what I'd like to get next is a solar filter, so I can do some of my observing during the day and not get so sleepy. I wonder what that will do—bring a succession of cloudy days to southern California?

11:30 p.m. 28 August 1998 PDT (0630 29 August 1998 UTC)

It has been quite a few days since the last time I observed (mostly because of sky conditions, but also because of stuff I had to do). Finally, though, the sky was clear, the child was in bed (he's a late sleeper), and I could get out for some reasonable viewing.

My first target, it being high in the sky, was Jupiter. Unfortunately, the GRS wasn't out, but the seeing was quite good, and I could see some detail in the belts; the NEB was solid (though not as colored as the last time I examined it), and the NTB (North Temperate Belt) was easily visible, with some offshoots into the NTZ (North Temperate Zone).

There was a bit of a coma effect on the moons, but because they were all in the same direction, I suspected collimation rather than a problem with the eyepiece. I trained the C5+ on Altair, which was conveniently at about 45 degrees altitude in the west (it's not comfortable to view things at zenith when I set up the C5+ on The Table, and when things are too low I don't trust the out-of-focus image enough to base my collimation adjustments). Sure enough, when I racked it out of focus, the shadow of the secondary was not centered in the blob. Fixing that problem took a bit of play on the adjustment screws, but eventually I got it back in the middle and the images of Jupiter's moons were back to being little round circles.

The star diagonal that comes with the C5+ is a prism diagonal, and it apparently has a reputation for not staying in collimation very well. So it's possible that it's the reason I have to play with it. On the other hand, there's certainly my tendency to not leave well enough alone. :)

I decided my next target would be M39, an open star cluster near Deneb in Cygnus. Because of how the telescope was set up, using the finder was next to impossible (without a tripod, there wasn't enough clearance between the finder's eyepiece and The Table), so instead, I decided to try to starhop directly at the main eyepiece, a laborious procedure, as it's almost ten degrees from Deneb to M39. Fortunately, the star field is relatively rich in this area, so I didn't get lost, but it was still fairly time-consuming.

(To get an impression of what this entailed, take a look at this map of the area. Deneb is the bright star at right side. M39 is the small cluster in the upper left corner. It's about one-fifth of the way in from the left edge of the map, and about one-third of the way down from the top edge. North is up. Stars shown to about magnitude 9. The field of view is about 13 degrees wide; by comparison, the true field of view at the eyepiece (with a 25 mm SMA) is about one degree wide.)

My last target for this short night was Saturn, which was just then rising over a wall. Now this night was a typical summer night in Santa Monica—reasonably warm, probably about 70. (That's 21 Centigrade, for you metric folk.) As is the case with those temperatures, the seeing is not always the best, but with the 15 mm Plossl in, I could see the Cassini division quite easily, once I obtained best focus (not a trivial task).

Then the temperature created bad seeing in a way that I hadn't anticipated. The wall that Saturn rose over belongs to the town house unit of our neighbor, and he likes keeping his apartment very cold. So I had only been observing Saturn for a few minutes when his AC compressor came on, and started blowing gusts of variously heated air directly in the path of Saturn. This created tremendous changes in how well I could see the rings. One moment I could see almost perfectly, and the next I couldn't see much more than a blur. These moments would last only about a tenth of a second, I'd say. The AC-induced seeing got steadily worse over a period of about ten minutes, so I decided that was my signal to stop and head in.

Just yet another hazard of being a late-night observer, I suppose.

Copyright (c) 1998 Brian Tung