Southern Exposure 2004

But the preparations! Not only do you have to travel - sometimes - for thousands of kilometers, often to really remote places: in this case either a desert area near the Northern end of the Fish River Canyon or a road next to the (diamond) "Sperrgebiet" East of Lüderitz. When you know where to go, you have to set up your equipment in a tiny strip that straddles the mathemetical graze line. Calculating the longitude/latitude matrix of the latter is difficult enough (especially as two leading codes for making these calcultations do not always deliver the same result). But then you have to make the fateful decision on how far from the theoretical graze line you position yourself. The database for these predictions is resting mainly on historical astrometry of photographs of the lunar limb, plus some lucky data points from previous grazes or solar eclipses that may or may not augment it. In our case the totality of data was confusing, to say the least: The Moon would slide by Alpha Lib 2 with a limb profile that was particularly ill known.

Now this would be my first ever grazing occultation, and going to the »risky« zone very close to the mathematical line was out of the question: There was a real chance - the experts believed - that the Moon would miss the star completely there. A few hundred meters »in« increased the chances of success, and after a full day of deliberations, renewed calculations (did I mention that occultation observers always travel with a notebook computer under their arms?) and site testing I had finally opted for the middle ground. Two observers (my travel companions) would be closer to the edge, two others (also from IOTA) farther in. Eventually we had written down that plan and signed it - mainly in jest, but it somehow made it feel more important. And then we had gone off into the desert - not a long trip now, because by sheer coincidence a nice little lodge, the Canyon Road House was located just a few km from the graze zone and formed a perfect base camp. No off-road driving was required either as we could position ourselves just off one of the few access roads to the Canyon.

While most of the others set up rather sophisticated equipment, with telescopes on tracking mounts and computers, I - as usual - planned to play it simple. Tests in the days before had shown that a regular camcorder would easily catch Alpha Lib 2 with its own chip and lens, and so I wanted to record the occultation by simply having the camera run, sitting on a tripod. But another reason why I had come to Namibia one week ahead of the other comet observers was my desire to have a look at comet C/2001 Q4 (NEAT) during the lunar eclipse. It was predicted to be near maximum brightness at around that date and the eclipse would be the only opportunity to see it without bright moonlight. And so I also carried a little telescope (a Celestron Comet Catcher, a more than 20 years old Schmidt-Newtonian with 512 mm F/3.64, sitting in a sub-Dobsonian mount) and a highly sensitive Mintron black-and-white video camera to my desert location at 27.55415° South 17.78837° East.

The final important step was to get a time signal and to copy it somehow onto the video tape. The IOTA experts had brought two shortwave timesignal receivers, and at night the beeps, one every second, were very strong. Since I would be 200 meters away from either receiver I had to »transport« the time to my place, and for that I used a simple stopwatch: First I filmed the running numbers together with the sound of the radio signal, later I recorded the watch's display before and after the occultation - without stopping the tape, of course - and then again the watch together with the time signal. This worked surprisingly well; remember, this occultation business was totally new to me and I had just »invented« this trick. And flexibility continued to be the key to success indeed, it would soon be apparent: There were patches of clouds moving around in the sky! Southern Namibia in May has by no means guaranteed clear skies: It's too close to the weather systems of South Africa, and the rainy season has ended not too long ago.

And so the eclipse/occultation developped into a race against time: Would the moon and the star be visible during the precious seconds? With the moonlight fading throughout the partial phase of the eclipse, the clouds themselves became harder to see directly - after all, there are no light sources whatsoever to illuminate them from below. But they made their presence known by dimming the Moon even more. Totality: Darkness has fallen over the desert, you can hardly see your equipment anymore, as the fully eclipsed Moon has now a very dark red color. Some of it due to the cloud patches, but it would also enter deep into the umbra. Had the regular video camera at first shown both the dark red Moon and Alpha Lib 2 (as well as its fainter companion 1), the view got fuzzier by the minute as the cloudiness seemed to increase.

And so I decide to change plans once more and to record the occultation through the Comet Catcher with the Mintron. Of course, more things go wrong: The »mount« of the telescope is a very simple and lightweight construction from plywood, cardboard paper and duct tape that holds the tube in place - and as the Moon is now pretty high in the sky, the tape suddenly gives way and the scope's tube slides down and now sits on the ground. So I'll actually have to support the whole setup - no time for repairs - with my hands throughout the whole occultation, tracking the Moon's limb by gently pushing the telescope over the desert sand and rocks ... But it works! Miraculously I get the right angle and focus, seconds before Alpha Lib 2 disappears! It's gone for much longer than anticipated (our experts were way too conservative, it now turns out) but then comes back, while I still somehow manage to keep it in view without shaking the tube too much.

The video recording came out surprisingly well, I can already report: The Mintron - running at the full 50 half-frames per second without any internal integration - did not care at all for the clouds that had already become pretty dense at that point, and the stars as well as the lunar limb are just brilliant. As I had to tend for the telescopes tracking during the event - by staring at the display of the camcorder that was now working as a VCR - I had not even noticed that the conditions had turned pretty bad. So bad actually that video recordings at two other spots were somewhat compromized (while two other instruments failed completely at the last moment). Even more amazing were the ingress and egress phases of Alpha Lib 2 when seen in slow motion: This were not instantaneous events at all. The ingress lasted 0.24 seconds during which the star faded with a constant rate until it was gone - this looks nice enough on the screen. But the egress was just amazing.

It lasted a full 1.2 seconds: During the first 0.32 seconds the star slowly appears again but remains very faint. For the next 0.56 seconds it hovers at a somewhat brighter level, constant but still much fainter than before the occultation. And only during the next 0.36 seconds does it grow again to the full former brilliance (this is all »visual photometry« from watching the video frame by frame). Such behavior is called a step event - and it proves, to my knowledge for the 1st time, that Alpha Lib 2 is not a single star. It was a suspected binary before, but now we know for sure! And from the very different ingress and egress profiles one may even be able to deduce the position angle of the at least two partners involved. Grazing occultations are a unique tool to study extremely narrow double stars as the Moon cuts very slowly through the line of sight: While it is still unclear whether the occultation of May 4 has taught mankind anything significant about the lunar topography, it has brought us at least the confirmed binary nature of Zubenalgenubi.

Key Links about the Graze To my knowledge, there are very few: a summary from IOTA on all observations (our group seems to have been the only successful one on record), a report (in German) from a different observer in S Namibia and Gabel's preview of the event [text content of website recovered with the WayBackEngine]. After seeing the latter I had analyzed the logistics somewhat. Ah, and there was a South African who photographed Alpha Lib just next to the eclipsed Moon but did not actually go for the graze: his pictures via IOTA and APOD.

... coming for the comets ...

Here is a first attempt to show both comets in "one" picture, based on 5 panorama shots I took on May 20, 2004, just after dusk, from the Matunda farm in Namibia. The color slides were each taken with 50 mm f/1.4 on Fujichrome 400, each was exposed for 30 seconds from a tripod. I had a lab make prints (that didn't come out too well) which I pasted together and scanned: The whole panorama didn't quite fit onto the scanner, though. Here is a rotated and somewhat enhanced version in which the two comets - LINEAR at the far left, NEAT at the upper right - are a bit more obvious. This is the case even more so in a black&white version (seen above in a smaller version), the contrast of which can be enhanced even more. Then the thin gas tail of LINEAR also comes out nicely. The 'light pollution' to the right of the tree is the zodiacal light, by the way, split in two because of uncorrected vignetting.

So now we know: Neither of them came even close to being a »great« comet like Hyakutake or Hale-Bopp, and you actually had to know where to look for them in the sky. And yet the double comet apparition of May (and June) 2004 was a unique experience, and it was worth to go after them, i.e. travel 75 degrees to the South. C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR) were both visible to the naked eye for several weeks each, and for nearly a week (i.e. from at least May 19 to 23) they could be seen simultaneously in the sky without optical aid, though some 80° apart - and such a constellation has not happened since 1911. As individuals both comets were rather umimpressive sights most of the time, even in binoculars or small telescopes: Faint comae not much exceeding 3rd magnitude and tails with low surface brightness.

Even with the next best technique, photography with a camera sitting on a tripod, both comets were not a striking sight, and even the LINEAR of 2001 was better that way as pictures from Zambia show. But observed with electronic cameras, the comet duo of 2004 was something completely different: Both for the simple Mintron video camera (now in integrating mode) with simple lenses or through the Comet Catcher and for still cameras like the Canon 10D the comet tails showed an amazing amount of detail. Plus, where the naked eye or binoculars would only reveal a few degrees of faint tail, the emanations of both comets often reached beyond the fields of view of the CCD cameras, showing lengths of 10 degrees or more in image mosaics. Even more impressive, the tails were changing, often from night to night, and expecially LINEAR was a master of surprise.

One morning or evening in May it would display a narrow plasma tail with little activity, 24 hours later it was strongly bifurcated, or a disconnection event in progress could be seen. A vast amount of raw video (15 hours by one observer alone) or high-resolution digital pictures was taken during the 2½ weeks of the main comet expedition, but it was fun to see the comets before and after as well. My very first view of LINEAR came before even landing in Namibia: The morning of May 2 was the last chance to see it briefly without moonlight - and I happened to sit on the right side (actually the left side) of the plane from Frankfurt to Windhoek. After some sweeping around with tiny binoculars I found LINEAR just as dawn broke somewhere over Angola (I suppose), sitting South of the Square of Pegasus. The tail was surprisingly bright that morning, just a week after the comet's perihelion, even with so little optical aid, and I never saw it that strong again.

The following week, when I cruised through the South of Namibia with my two IOTA fellows (racking up almost 2000 km), had its share of comet views, too. At first the Moon was extremely bright in the evening sky, drowning out much of NEAT for the eye. But the coma, still pretty big then, and the dusty tail nonetheless showed up nicely in Mintron views - and on untracked chemical still photographs as well. A counterintuitive effect of the photographical process (which I »discovered« in 1982 and termed LPUP, light-pollution-aided unguided photography) was at work here: When the skies are cloud-free and transparent but moonlight (or terrestrial light pollution) is present, the sky background goes up so much that it pushes the film's response into the linear regime. Faint diffuse structures - gas nebulae in particular but also comet tails - that would normally hardly register at all suddenly become imprinted nicely on the emulsion, with the aid of the »unwanted« diffuse photon bath.

This effect is well-known but hard to control - and it continues to surprise me. For example during the May 4 lunar eclipse pictures of NEAT taking during the partial phase came out much better than those during totality (when the extra photons were »missing«). And the next evening, when the still nearly full Moon was near the zenith and so bright that the sky looked a light blue to the eye, with hardly any stars visible, the comet photos taken that night - when I couldn't see NEAT with the naked eye and didn't even bother to try with binoculars - were the best of the whole trip! For the strictly linear CCD chip of the Mintron, of course, the opposite rule applies: It can only play out its full sensitivity when the sky is really dark. Fortunately this happened promptly: Already on May 6 a brief moonless interval existed in the evening - and as our group was out there in the desert somewhere, late as usual, we could make full use of it (plus watched the Moon rise over distant hills - this can be a striking view, too).

The dark evening window grew in length every day now, and hardly did I miss the opportunity to watch NEAT both fade slowly and move from Canis Major towards the North. On May 2 and 9 I also had the opportunity to look at NEAT's innermost comet with high magnification through a Celestron 14 at Sonja Itting-Enke's observatory near Windhoek where both expeditions found wonderful hospitality and where I stayed for three nights: There were some dusty structures near the nucleus (evident by their yellowish color), but few details were evident. In the 2nd week of May, when the actual comet expedition commenced, NEAT would also become visible for Europe - but LINEAR would not: This comet, still stuck in the moonlit morning skies and checked for only occasionally, was still to reach its maximum brightness and would be visible well only South of the equator. On May 17th this comet would move rapidly by the Sun and appear in the evening sky, joining NEAT: For these double-comet-days we had made arrangements to stay in one place, but before that our group travelled around a bit.

First we paid a visit to the famous Hakos farm (where many German amateur astronomers tend to end up for very serious work but which was now booked to and beyond capacity by a group from Vienna): In the evening we watched NEAT set, and rising LINEAR fought nicely against the Moon with its long plasma tail (that was forked more dramatically than on any other day we looked, the Mintron revealed in realtime). The next few days were spent at the coast in Swakopmund (where we liked it so much that we stayed one day longer than planned): Heavy light pollution and frequent fog put a momentary brake on serious astronomy (instead we enjoyed the gastronomy all the more :-), but it was still possible to follow NEAT's approach to the open star cluster Messier 44 (the Beehive) from our hotel's garden. Not even tripods were needed, by the way: It was possible to »mount« a Mintron directly to a birdhouse and still get decent comet videos ...

Then came the most romantic of comet nights: On May 14 we camped out next to the Spitzkoppe mountain in an amazing eroded rocky formation, really far from any artificial lights. Catching NEAT in the evening was still easy as it materialized some 50° up when dusk fell - but LINEAR, already pretty close to the Sun, was another matter. Using detailled predictions for its azimuth and elevation (calculated with the enormously powerful JPL Ephemeris Generator) and a compass I had directed our group's old VW bus to a camp site from which LINEAR should rise between two distant rocks the next morning - and it did! Although the waning crescent Moon was of some nuisance, LINEAR's long and narrow plasma tail could easily be imaged that morning, raising further hopes for an interesting simultaneous comet duo in a few days time. On the 17th we arrived at our destination: the little guest farm Matunda we had scouted out on the web (they hardly do any classical advertising), not known at all in the astronomical community - until now.

Located just 11 km from the small town of Outjo, on the road to the Southern gate of the Etosha National Park, Matunda suffers from a bit of light pollution, but only in the low Southeast. In the Southwest and Northwest, where our comets were to appear, the skies were perfect - and there was even a nice large African tree, in a perfect bearing to be placed between the two comets in fish-eye views. To make use of this perspective we had to set out all our telescopes on the main road leading to the farm house - but this was no problem for the owners who even helped us fight back the ubiquitous dust with a huge tarpaulin. The setting was almost idyllic, with lots of varied vegetation (but not in the critical directions, as I checked with the compass) - a dramatic contrast to the barren landscapes of the deep South of Namibia. And still the prospects for clear skies were decidedly better here than down there, as one of us had found out by comparing satellite images of the last few years. Reality, to our amazement, would comply nicely.

We lost exactly one night due to clouds, May 18, during the whole 3½ weeks, and even then managed to catch both LINEAR - now in the evening skies but barely above the horizon - and NEAT through gaps. Other sites farther South, we later learned, lost several nights around that time. The clouds were gone the next morning, and the prime time for the comet duo began: On May 19 but especially on May 20 and 21 they were easiliy visible to the naked eye at the same time and without any moonlight. While LINEARs long tail in the Southwest was pointing towards the upper left, NEAT's, in the Northwest, was at a right angle, pointing to the upper right. This was an awesome sight, even with the comets at near 3rd magnitude - especially when you remembered that the last naked-eye comet pair came in 1911, when Namibia was still a German colony. If you really looked hard, you could follow LINEARs plasma tail with the naked eye for some length now: It looked somewhat like comet Hyakutake if one would have observed it with sunglasses ...

Even when the Moon came back with force to the evening sky, the visibility of the comets didn't suffer much: Especially LINEAR remained an easy sight - even on the very last evening when I caught it with the naked eye from the very center of Windhoek on May 24. NEAT had become difficult for Southern Africa now as it was heading towards Ursa Major - which, on the other hand, made it visible all the better for Germany to which I returned briefly. Both from my backyard on May 26 and from the Bruder Klaus Heim in Violau (Bavaria) where the annual national meeting of planet and comet observers is held on May 28 and 29 NEAT was obvious is binoculars, despite the strong moonlight. The same techniques as used in Namibia were applied once more, and NEATs dusty tail plus plasma component could once more be extracted, though less glorious than in the previous weeks. But what had happened to LINEAR which continued to be inaccessible from Europe?

On June 4 I saw this comet again, under horrible sky conditions from a suburb of Pretoria in South Africa: It was easy to find, next to an isolated and very bright star in Hydra, but under these conditions just the coma could be detected. It was surprisingly bright, though, more than one month after that comet's perihelion. Two days later I could see LINEAR again, under much better conditions from a lodge at the edge of the Pilanesberg National Park. And on the evening of June 8 - the day of the Transit of Venus - the skies were perfectly transparent: Now LINEAR, very high in the evening sky, could be spotted one last time with the naked eye. And in binoculars (and for the Mintron) it was a sight even better than the previous month: The tail was much shorter now, but the surface brightness seemed to be higher. And near the Northern horizon even NEAT, now at the »feet« of upside-down Ursa Major, was an easy binocular sight. What a grand finale to a unique double comet show!

Key Links about the Comet Duo Lüthen has analyzed his 15 hours of comet video from the trip - amazing pictures! Another comet expedition in Namibia reports via the DCP. And when you follow the "Hakos" links in this collection of Austrian observations you see what the Vienna did during their stay at this farm (plus find long reports about the whole trip by Hartl and Schröfl as well as a dedicated website by Schefler from later that year, w/o the comets). F. Viladrich also has a few pictures of NEAT and LINEAR, taken from Angola. The only view of both comets in one picture I've found on the web so far is from Australia (but we have better ones). Many more links about the comets can be found in story 3 of the Cosmic Mirror # 277 and in MegaLithos Online News Nr. 900c. And to see how the expectations regarding the comets developped over time (until the end of April 2004), check this English/German collection, with further links about the comets.

... and travelling to the transit

Behind the veil: a transit has begun ... (all photos in this chapter by S. Hüttemeister)

The white guy in front is me - and the thing in front of me is the
Russentonne with solar filter I used both visually & photographically

The students were eagerly taking notes; obviously they had to write a paper on their experience ...

Projecting the Sun with the help of a large dobs turned out to be the most crowd-pleasing approach

World-class astrophysicists observing with their own eyes ...

The egress as imaged by Bert van Winsen from the Bakubung Lodge -
click on the image to get more frames and a full-resolution view!

Key Links about the Transit of Venus Countless links can be found in the lead story of the Cosmic Mirror # 277 and MegaLithos Online News Nr. 905 and 925. Other sites about the transit in South Africa (that Google found): viewing the transit at Jo'burg Planetarium, the Univ. of Pretoria and the HartRAO (they all shared our weather fears), preview sites from SAAO and Jo'burg Planetarium, an AFP story on what the Zulus think, an AFP photo in which a "South African healer calls upon Venus to bless Earth with abundance as he watches the planet's transit," an ad for a luxury VT tour by Astronomy Vacations to the RSA and some Dreams of Fire (whazzat???).