OASI: eclipse

By the mid-1990s I had already seen several solar total eclipses and was keen to record photographically all the different aspects that they presented: Baily's Beads, the chromosphere, the corona, the shadow and so on. This really requires more than one camera and I found that it was very easy to spend the entire period of totality fiddling with knobs and buttons and looking through a viewfinder. I required automation!

I developed my first round of automation for the 45 second eclipse visible from India in October 1995. A simple circuit based on a 555 timer opened and closed a pair of relays. The relays were connected to a pair of cameras so that they periodically took wide-angle pictures of the shadow while I used two other cameras. This worked well - the only problem was knowing when to turn it on.

For the next eclipse, Mongolia in March 1997, I wanted something more sophisticated, something with an onboard clock and the ability to control several cameras. Unfortunately, although I had started construction of such a system, I did not complete the project in time so took the 555 timer to the eclipse. In the event the eclipse was clouded out but the 555 timer did control a camera that showed the darkening of the sky as totality approached and the lightening of the sky when it departed.

For the next eclipse in Curacao in February 1998 the more automated system was ready. This was based on a Psion 3c organiser and a custom built relay box that could potentially fire up to 8(!) cameras. See [1] for a description of this system. It was not fully automatic as there was no means of changing the shutter speed when photographing the corona - this camera was partly manual and I still spent too much time looking through a viewfinder.

For the August 1999 eclipse in Turkey I rolled out my final step in automation. The camera I used was a Pentax ME Super with a power winder. It does not have the conventional shutter speed knob but a pair of buttons, one to increase the shutter speed and one to decrease it. This was quite a novelty when it was launched in about 1980. I did not want to perform surgery on a perfectly functional camera and instead decided to arrange for shutter speed adjustment by a solenoid held over one of the buttons. This was the first eclipse during which I could leave the picture-taking to a machine leaving me free to enjoy the spectacle in person without looking through a viewfinder. So, did it all work? Of course not! The eclipse occurred on the very day that the solenoid wiring somehow developed a short circuit. The battery became so hot that the spring terminals melted their way out of its plastic holder. As a result, the speed-changer did not work and I ended up with 27 pictures of the corona all taken with the same speed. They were nice but I didn't want 27 of them!

Onto 2001 and Zimbabwe. I discovered that the buttons that adjust the shutter speed merely connect a line to ground, so if I could extend this function to a relay outside the camera I could control the speed. By chance I was able to obtain a partly disassembled ME Super from which I learnt a great deal about how I could extend the up and down buttons through the flash hot shoe and how to both disassemble the relevant parts of the camera AND reassemble them. Using the hot shoe (and disabling the flashgun functions) provides a really neat way of joining the relay to the camera - thanks to Nick Quinn for this tip as he has performed an identical operation on a Canon T70.

And did this work? Yes and no! The speed changer worked brilliantly under the direction of the Psion-controlled relay box, first increasing the speed and then decreasing it. Unfortunately the power winder underneath the camera did not co-operate: each and every picture was blurred because of a kick given when the shutter opened. Yet it was the very same power winder I used two years previously. To this day I do not understand what went wrong but of one thing I was certain: I was not going to waste any time trying to fix it. The Pentax was not going to the next eclipse!

So, on to December 2002. One of my early purchases was a replacement for the Pentax ME Super. The more modern cameras have a thumb-wheel that can control different functions, so don't obviously lend themselves to the sort of modification I was planning. I knew of only one camera that would do the job - a Canon T70 (which has an integral motor wind). None of my other cameras have the FD fitting but this was a "special project" camera that does not need to be compatible with anything else. There may even be other suitable cameras but I knew from Nick Quinn's experience that the T70 could do the job. Testing with the Psion showed that, by keeping a tight check on the times needed to change shutter speed and take pictures, it was possible to go from 1/125^th to 2 seconds exposure and back in 24 seconds. It is not possible to follow that sequence so quickly by hand.

Two things made this eclipse different from all the others that I have seen: the low altitude of 6° and the extreme brevity of 26 seconds. The low altitude meant that the Sun and everything else would be darker than usual due to absorption through a thicker layer of the atmosphere. This meant that the exposures should be longer than for a "normal" eclipse with the Sun at higher altitude. I estimated that a 2-stop increase would be sufficient to compensate. The extreme brevity meant that all cameras would be operating almost simultaneously and that running out of film would not be a problem (in fact it would be difficult to use all the film).

Eclipse-viewing equipment has to be light enough to fit into the airline baggage allowance for two people, so making things as light as possible is essential. I made wooden clamps if I could, instead of metal ones. My main effort was in making mounts for the two main lenses. I rejected the idea of an equatorial mount, which would make it much easier to move the cameras to follow the Sun, as it was both too heavy and unnecessary for such a short eclipse.

On previous eclipses I have had two long focal length cameras mounted together on the same (equatorial) mount. Vibration from one camera did not affect the other because they were used alternately - the long lens took photos at 2^nd contact then the 500 mm lens took pictures of the corona, then the long lens took pictures of 3^rd contact. However, in December 2002, there would not be enough time to operate the cameras alternately in this way. For this eclipse the mount on top of the tripod was a custom barn-door mount with the hinge pointing towards the South Celestial Pole (SCP). Once approximately aligned only one axis would need to be adjusted to keep the Sun in the field-of-view. I planned to locate the SCP by using a plumb-line sundial drawn for the place and date of the eclipse. Testing of a f/10 1000 mm lens on top of the tripod and a 500 mm lens clinging to one of the legs convinced me that it was possible to run the two cameras simultaneously without any mutual interference. (I did test an ETX 90 instead of the 1000 mm, but it was more susceptible to shutter vibration as it weighs only half as much as the 1000 mm lens).

The second tripod would carry the other three cameras with shorter focal length lenses, where the mutual effects of blurring are less noticeable. Attached to the leg of the tripod would be a camera with a 250 mm lens that looked downwards onto a diffraction grating that itself was mounted on the ground. This would record the chromosphere which, being principally composed of hydrogen, glows primarily in certain wavelengths. The diffraction grating then splits the light into a series of distinct images of the chromosphere. Midway up the tripod would be a 16 mm fisheye lens to capture a wide-angle view of the shadow of the Moon. At the top of the tripod, looking straight up, would be an 8 mm fisheye lens to give round images of just about everything in front of it. If there was a time to catch the asymmetric shape of the lunar shadow then this should be it.

We travelled with Explorers Tours, flying first to Hong Kong, where we sampled the usual sights - Victoria Peak by day, the Peak Tram, Victoria Peak by night, the Star Ferry, the night market, afternoon tea in the Peninsula Hotel, and so on. One of the more unusual buildings on Hong Kong Island is the Lippo Towers. They look as if they have koalas clinging to their sides, reflecting their original owner - Australian Alan Bond. Don't read the next part of the paragraph if you are eating. One of the lesser tourist attractions was a visit to a shop selling Chinese products, in particular the food hall. The Chinese are well known for eating virtually any part of any animal and this shop had a wide selection of things we couldn't recognise and didn't really want to identify. The fruit-based food looked quite nice - indeed we bought some ginger there. The wine display looked harmless, with wines from different parts of China. We then found some wines labelled "tonic wines", but this had nothing to do with gin. There was snake wine - floating inside the bottle was a small snake. Gecko wine had a drowned gecko and three snake wine had (parts of) three different types of snake. At the end of the display was yet another - field mouse wine. Sure enough, there were the corpses of six small mice (an entire family?) hovering near the bottom of the bottle.

Then it was onto Sydney, where we took in the harbour, the Blue Mountains, Featherdale Wildlife Park, Sydney Tower and the Aquarium. After the day tour to the Blue Mountains we met up with Nick James and went for dinner. The kangaroo was very tasty indeed.

We travelled from Sydney to Adelaide. At lunch time on Tuesday 03 December John Mason gave his usual entertaining talk on what to expect at the eclipse site. Apart from being hot there would be the problem of creepy-crawlies (ants, scorpions etc). I expected to be out in the Sun the next day assembling my viewing equipment - during this I might want to sit on the ground yet did not want to be bitten. I pondered how to resolve this problem... After a restful afternoon we met up with Nick James at 5.00pm to go shopping, not realising that everything shut at 5:30! Through the window of a surplus store we saw just the solution to my problem - a buy one get one free offer on some camping chairs. Shame the store was shut. As Nick was on the coach to Woomera early the next morning, we decided that Alex and I would buy a pair and then rendezvous on the eclipse site. Two collapsible "film-director" chairs for a total of AUS$30 and a three-legged fishing stool for AUS$11, about £15 the lot! Nice though they were there was no prospect of bringing them back to the UK.

The day started in the traditional Explorers' Tours fashion - getting up at a ridiculously early hour for breakfast before departing to the station to catch the train, then having a second breakfast at 7.30am. After breakfast on the train we spent some time partially assembling the tripods and the mounts that clung to them, loading the cameras with film and assembling the barn-door mount for the 1000 mm lens. After lunch we arrived at Pimba and set off for Woomera, where we toured the open-air museum under absolutely clear skies, then indulged in a spot of retail therapy for eclipse souvenirs. There we bumped into Pete and Nicky Richards from OASI. Then off for a short tour, passing the CANGAROO gamma ray Cerenkov telescope [2] then stopping at the ELDO Launch site at Lake Hart, where we bumped into Dr Steve Sweet. Last stop - the eclipse site.

Upon exiting the bus at the eclipse site, the first thing to hit us was the WIND! This was a real kite-flying wind, maybe 30 knots, but also mercifully much cooler than the 35°C or so that we had expected. The only dust about was that lifted by the coaches as they approached - fortunately blowing away from the both eclipse site and the Sun. The sky was still absolutely clear, and remained so for the rest of the day. The eclipse site itself was a long thin strip of land within the Woomera Prohibited Zone that gave all the observers a good view of the Sun during the eclipse. I don't think I've ever been anywhere where the landscape was so flat. Even the plants were very short, only 15 cm or so (after all, Woomera is in a desert). The boundary of the observing site was marked by a white chain link fence, behind which we were supposed to remain, as there was a theoretical risk of unexploded munitions beyond.

Choosing a pitch was made remarkably easy as they were all the same! Up with the chairs and off to work, following the script that had been written beforehand. Assembly of my kit went pretty smoothly, except for the problems caused by the wind that was coming from the direction of the Sun (no "solar wind" gags please!) The plumb-line sundial was a dead loss. The group next to me seemed to have one as well. In the end I just had to guess the direction of due south from the location of the Sun. The longer lenses had Baader solar filter material on the front. The main concern was for the 1000 mm lens - a combined solar filter and sunshade on the front of it had the wind pushing onto the filter. I was worried, whether justifiably or not, that the wind would push the filter material out of its mount - not very amusing if I happened to be looking through it at the time. I found it strangely difficult to focus on the Sun through this filter - I could not obtain a sharp image. The 250 mm lens and camera on the tripod leg (for the flash spectrum) had images that were dancing all over the place, with a real risk that the small tripod carrying the grating would be blown over. Enter one large rock to hold the small tripod in place. The images didn't stop dancing about though, as the camera with a 250 mm was side-on to the wind and could not be protected.

As I had a pile of cameras to attend to I was rather immobile - sitting on the chair also stopped the wind blowing it over, as happened on at least one occasion when unoccupied. This meant I could not go and wander down the line to meet old friends. However a few did manage to drop by on me. Shelley Fey, a veteran of many eclipses showed up. So did Fraser Monks, a New Zealander I met in Turkey in 1999.

As totality approached I felt remarkably calm, probably because everything seemed to be in order, as much as the wind permitted. I made a quick last adjustment of the two long lenses to ensure that the Sun was in the centre of the field of view. The first of the cameras fired at 30 seconds before 2^nd contact, indicating that it was now too late for fiddling and it was time to just sit back and enjoy the spectacle. A tremendous cheer went up at 2^nd contact and it was now the time to look at the shadow, the corona and - what's that on the horizon? Valuable seconds were wasted realising that someone, several miles in front of us, was letting off fireworks!

All too soon the Sun reappeared, signalling the end of totality. And I didn't see it through the rectangular frame of a camera viewfinder. I was elated - I felt as if all the time and effort put into planning had paid off. A quick check of all the cameras showed that the film had been consumed in the correct amount, except for the 1000 mm lens which showed only 26 frames used instead of 33 planned. I could not do much about that now. Time to start packing up, but keep the camera with the long lens for later - sunset of a partially eclipsed sun, something that I had never seen before. I took several frames of the sunset and managed to record the green flash on several of them. (In the images below, the montage of sunset pictures was taken with a Russian 1000 mm f/10 telephoto using a Canon EOS500N on Elitechrome 200 at 1/2000 sec, the fastest shutter speed available. The lens weighs about 2.5 kg - I think it used to be a part of a tank barrel! The six frames are sequential and the camera was positioned only about one metre above ground level.

On to the coach and off to the post-eclipse barbecue. Hmmm! Not one of the culinary high-points, I'm afraid. The barbecued food was cold, the site was so dark that we could not see what we were eating and the musical entertainment was, well - rural. Still, we managed to catch up with Nick James and John Mason for a beer before we had to depart for the train for the overnight journey to Alice Springs.

From Alice Springs we travelled the 400 km or so to Uluru. At Uluru, clouds unfortunately obscured the sunset, but the sunrise was clear. On the 1500 km overnight journey from Uluru to Adelaide the train was able to stop for about 40 minutes in the middle of nowhere. We all piled out to see the southern sky and I attempted some star trail photographs - however, the film in the cameras at the time was not what I would have chosen, so the pictures are not brilliant. Then we travelled from Adelaide to Melbourne via The Overland; the cabin accommodation on this train was similar to the previous days' but the dining car was not nearly so luxurious. In Melbourne we went on the evening tour to Philip Island to see the penguins coming home at sunset.

How did the pictures come out? The 16 mm fisheye pictures were disappointing because they were all of a fixed exposure and all overexposed by at least one stop. The horizon colours were bleached. Mercury was visible in some of the pictures of later stages of totality.

The 8 mm fisheye lens gave all-round images of the sky that were OK. It captured the horizon colours well but the actual zone that showed them is surprisingly narrow - a large part of the frame is dark blue. It did not record Mercury; not that I expected a lens of only 2 mm effective aperture to achieve this.

The 250 mm lens with the diffraction grating worked well but suffered from buffeting by the wind. Whether it was movement of the diffraction grating or the camera (side-on to the wind) or a combination of both, the effect was to blur the pictures. A few of the shorter exposure pictures were reasonably sharp, but none of the long (half-second) exposure frames were.

The 500 mm lens worked a treat. The camera set shutter speeds from 1/125^th of a second up to 2 seconds, then back down again to capture the corona, under the control of the Psion. One of the 2-second exposures did show a slight hint of blurring from the wind but the exposure was probably in excess of what could show the outer corona. The background sky was quite bright in those images. The camera also took frames before 2^nd contact and after 3^rd contact, when it imaged the last part of the photosphere on one side of the Sun together with the inner corona and some prominences on the other side. These revealed something I did not want to see - they were out of focus, not a lot but it meant the other photographs of the corona were also out of focus.

Lastly - the 1000 mm lens. For some reason the camera only took 26 instead of the planned 33 frames. Once back home I re-tested the camera and it took 33 frames, so the reason why it took only 26 of the eclipse remains a mystery. So the absolute chronology of the eclipse frames was lost, as I did not know which were missing. But worse was to come, as each and every frame was out-of-focus! I was devastated. And it was a focus problem, not blurring due to wind-shake; frames damaged by the latter were easy to identify.

To find that the two long lenses were both out of focus was extremely disappointing. I have yet to work out what went wrong. Certainly the wind was a factor in preventing me from looking through the long lenses. The solution to that will be to buy the metal-on-glass filters (which I have for the ETX), which will not be at risk of being compromised by a head-wind. As far as I recall the lenses looked in focus when I aligned them on the Sun in the closing minutes before totality. In the coming months I will test the two lenses. Temperature change is a possibility, from the cooling caused by the Sun being obscured by the Moon. I will also study closely my eyesight to see if there something wrong with it.

The night-time shots were OK. The 8 mm and 16 mm shots were on slow film, so got a rather hard scan. I am pleased with the 50 mm shots of the polar region. The longer exposure captured stars in the polar region fainter than magnitude 9.

In spite of the disappointment with the eclipse photographs I nevertheless had a thoroughly enjoyable time in Australia and Hong Kong, met some wonderful people and, most importantly, saw the eclipse under perfect conditions.

I am afraid that the next two total eclipses, in 2003 and 2005, are both out of range of my wallet. The next total eclipse of the Sun that I expect to see will be in 2006. The eclipse will be longer and higher in the sky, so some of the unique features of the Australia eclipse will not apply. I expect I will have bought a digital camera or two by then and maybe the Psion 3c (brand new in late 1996) will have been retired.

16 mm fisheye lens.

Montage of images of the corona with 500 mm lens.

Montage of images of the corona with 1000 mm lens.

Corona, 1000 mm lens.

Flash spectrum, 250 mm lens.

Montage of images with 500 mm lens close to totality.

16 mm fisheye view of the eclipse shadow by Alex Evans.

A very happy Nigel at the end of totality!

Montage of sunset pictures. Note the green flash visible on the middle two.

Green flash on the setting Sun.

Green flash on the lower horn of the setting Sun.

Southern polar star trails.

References

Paul Whiting, Woomera, Australia

July 2000: Where shall we go to see the 2002 eclipse? The choices were South Africa, specifically the extreme NE tip of the Kruger National Park or Zimbabwe (safaris, animals - sounds good), or Australia (dry desert, spiders but no bullets). The choice boiled down to one thing, the weather, and specifically the likelihood of a clear sky. The obvious choice was to sacrifice duration to maximise opportunity to view, therefore we chose Australia.

The main town on the centre line was Ceduna - a two horse settlement with one hotel. The hotel still had vacancies but the town as a whole had just started to realise that something special was due to happen in early December 2002, and was expecting so many visitors that a new sewer was being installed! However, in the end we decided to use Explorers Tours, as they had previously provided a good service and, indeed, they did so again, facilitating a successful trip for the eclipse and for all the add-ons. You cannot go to the other end of the world for just 26 seconds! Three weeks sounds a lot better.

November 2002: Flying into Adelaide, via Bangkok, we got ready for the run up to the big day by visiting several vineyards in the Barossa Valley (Jacob's Creek wine). The day before the eclipse we were issued with security bracelets, which we had to wear for three days, and were taken to the Woomera Restricted Area - a former military zone covering an area larger than Wales. Following the Second World War, Woomera was used jointly by the British and Australian governments as the site for several rocket and satellite launches; nowadays it is operated by BAe and used for weapons tests, but not any longer rocket launches. We were staying in the ELDO "hotel", where the European Launch Development Organisation billeted their staff in the 1960s. The rooms left something to be desired but were functional.

The night before the eclipse we were given an orientation lecture on eclipses - what to do and what to expect, as there was a large number of first timers in the party. However it was still very interesting for the more experienced - there's always something to learn. Later that night we were taken by coach to a dark site, miles from the nearest artificial light, well inside the Restricted Area, and were given a conducted tour of the perfectly clear southern night sky. Wonderful! Especially the SMC, LMC and an upside down Orion. I also took the opportunity to make naked eye and binocular observations of the Pleiades for OASI's Pleiades Observing Project which was underway at this time. But boy was it cold! By day, 26°C, by night approximately 3°C. Back to the hotel by 2am. Sleep and late start for a morning at leisure on the day of the eclipse.

At noon we boarded coaches and were again taken to the interior of the Restricted Area. To start the afternoon we were treated to a ride round some of the site, seeing some old launch sites, rocket test ranges, some high energy particle telescopes and the odd kangaroo. About four hours before the eclipse we were taken to our viewing site. BAe had done well: they had levelled a mile long, 100 m wide track in the middle of the outback desert and placed a ribbon fence along which we would set up our equipment. There were probably a dozen "enclosures", one reserved for each tour group. There must have been approximately 2000 observers, including Pete and Nicky from OASI, who had somehow managed to sneak into our private area!

Bearing in mind that we were in the middle of the outback with nothing but red sand, some scrub bushes and the occasional emu, the facilities provided were excellent: portaloos, the famous Ozzy barbie and a cheap bar (iced beer). We were told to drink at least one litre every two hours, but I think they meant water rather than iced beer! In fact there was everything you could possibly want - except a chair. The red dust got everywhere so you couldn't sit on the ground.

The shadows got longer and longer, and eventually the eclipse started. The wind had been blowing all day, causing a lot of sand movement so we had to keep the cameras covered with plastic bags on their tripods until the last minute. At long last the countdown to totality started. All the observers fell silent. Even the wind dropped a little. Even though the eclipse was just before sunset and hence at very low altitude, there was not a cloud to be seen and the Sun entered totality spectacularly. But as soon as totality started, it finished - 26 seconds isn't very long! I captured some good video footage (see the two stills below from the video) but unfortunately my photos did not come out.

Totality.

"Diamond ring" effect at end of totality.

After the Sun set in eclipse, we all wended our way back to the ELDO for another barbie, and on with the holiday.

We seemed to have had the best location: Ceduna had some cloud and further north, along the Stuart Highway, they had trouble with dust storms, but everyone saw something of the eclipse. We were told that the Explorer's party in Africa missed the eclipse altogether due to cloud cover.

In the following fortnight we looked into the possibilities of the Antarctic eclipse in November 2003. A firm in Perth had hired a 747 to fly over the South Pole - but at AU$1100 for an inside seat with no window I thought this was a non-starter. Other thoughts included a five week boat trip from Australia, New Zealand or Argentina at around US$12000. Perhaps we'll give the Antarctic eclipse a miss; there is, after all, an annular eclipse visible from Orkney in May 2003.

Nigel Evans, Woomera, Australia

A Nerd's Grand Day Out - The Story of Heroic Failure

References

Paul Whiting, Woomera, Australia

More Information on Eclipses