Gotcha, again: tons of Beads and the chromosphere caught during annular eclipse

Even the thick ring of October 3, 2005 - as seen in excellent skies from close to the Sahara desert in Tunisia - couldn't stop a daring astrophotographer ...

By Daniel Fischer, Königswinter, Germany

The central phase of the eclipse as seen from our site near the northern edge of the zone of annularity - and a splendid chain of Baily's Beads cutting into the arc of chromosphere between the crescent horns seconds after the ring broke up at 3rd contact.


Leading up to the ring phase: the chromosphere begins to appear between the horns of the crescent into which the Sun has shrunk, soon to the punctuated by a growing number of Bailys Beads where the solar photosphere peeks through lunar valleys. Then the chain of Beads merges into one thin line, and the ring is closed.

Phases of the eclipse, close to its dramatic maximum (sorry, this being my 19th »full-silhouette« eclipse and the 15th clear one, I just don't bother to shoot the partial phases anymore :-). With the exception of the center shot, they are deliberately overexposed to bring out faint detail at and inbetween the crescent horns.

There goes the ring - and what a way to loose it! At first some lunar mountains cut the ring into pieces, then those arclets shrink into isolated Beads which disappear behind the Moon and leave an arc of chromosphere, plainly visible for several seconds before being lost behind the Moon, too (but then the film was already full).


To see the full set of pictures - on a black background - click here,
and to see the (approx.) times and all techical data
(plus a report on a workshop held about this eclipse in November 2005), go here!!!

These pictures were taken with the famous »Russtentonne«, a Russian Maksutov telephoto lens with 1 m focal length and f/10 that was purchased in 1993 and has now joined me for its 9th solar eclipse since 1994 (6 total and 3 annular ones). For the first time at an annular eclipse (this being my 7th) I was shooting on print film (Fujicolor Superia 100), for its great latitude would be needed for the extreme contrasts to be expected during a thick-ring annular. The idea was actually spawned by the wild experiences during the hybrid eclipse ½ year earlier in the South Pacific - which I always treated as trial run for the »real« eclipse in October. :-)

Most of the time I was either shooting through one layer of »Rettungsfolie«, a metal-coated mylar(?) foil found in German first-aid kits to keep accident victims at temperature: It has much less density than a typical photographic - let alone visual - filter, and you can easily see the landscape in daylight when you hold it in front of your face. But when going for the »meat« of an annular eclipse, those highly dynamic phenomena at the very tips of the crescent horns and the tiny Baily's Beads of photospheric light, filters of this low a density are a better choice than those used for normal solar disk photography: They take care of the substantial darkening of the very limb of the Sun which is what we are looking at, of course, and not the much brighter center of the disk.

The view of the solar crescent in the viewfinder of the SLR - an old Canon AE-1 Program, its shutter still sounding strange because of remnant dust from the 1995 Rajasthan eclipse :-) - is dazzlingly bright, so for centering and focussing the Sun precisely, another layer of Rettungsfolie helps (or would have helped; the focus setting was not too good before 2nd contact though improved later). But an amazing lesson I learned from the 2005 annular experience is that when you use print film, you can shoot annular solar eclipses without any filter! Most of the pictures shown above were in fact obtained by pointing the Russentonne at the Sun completely unprotected.

This way of operating is very risky, can be hazardous for your eyes and should never be tried without many precautions!!! In particular you are absolutely not allowed to look through the SLR viewfinder anymore after the last layer of Rettungsfolie is removed. And it must be guaranteed that the mirror flips right back after every exposure, guiding the barrage of solar photons out of the camera - otherwise the shuttler would probably burn through in no time. For recentering the Sun once in a while (necessary when operating from a simple photographic tripod as I was using) the foil has to come back on first: A simple hinge mechanism pasted to the Russentonne's front helps a great deal in swiftly changing between filtered and unfiltered views.

As it turned out during the 2005 annular, which was observed at an elevation of 45° through cloud-free and pretty transparent skies, working at ISO 100, f/10 and 1/1000 sec exposure only pictures shot through two layers of Rettungsfolie - which together mimick a typical photographic solar filter, albeit at lower optical quality - result in what one could call the correct density on the negative. Correct with respect to the main part of the solar crescent, that is, not the subtle near-limb phenomena we are after. Pictures with one layer of Rettungsfolie are heavily and those without any filter extremely overexposed, i.e. the negative looks pretty dark: The thick photospheric crescent left free by the Moon and scattered by the atmosphere and the optical and film surfaces alike takes a heavy toll.

A slide film would be more or less white, without any chance of recovering the things that interest us - but print film has so much more latitude that the faint Beads and the chromosphere can be extracted from the darkish »mess« on the negative even by ordinary photo printers (the lab operator just has to set the density control near max) or film scanners: The pictures above were all created by moderately processing such scans. And because the additional optical artefacts that the Rettungsfolie introduces are absent, the extracting and processing task is actually easier than when working with negatives shot through one layer of Rettungsfolie. I have no idea how the CCD chip of a digital SLR would react when treated with the same approach ...

It takes a certain boldness to go after an annular eclipse without any filtering and the author wishes to discourage everyone but the most experienced of solar and eclipse photographers from even starting to experiment with this technique, but the results can obviously be quite impressive. The idea - which had been inspired by fine results by others in the 1990s - had worked for me already once before and beyond all expectations, during the 1999 annular when the remnant ring was much thinner. But now I know that it can be be done (minus the detection of the inner corona, though) with a thick-ring eclipse, too - and it is now clear, too, that the internal reflections of the Russentonne are no showstopper either.


The eclipse making news on the front page of the Tunisian newspaper Assabah on October 2nd - apparently a picture from the 2003 sunrise annular over Iceland was used, albeit tilted by 90°.

Eclipse day was the second-best of the seven days I spent in southern Tunisia: Most of the others were severely affected by cloud bands from a vast low-pressure system over the Mediterranean - incidentally European meteorologists had code-named it »Boris«, just as the infamous tropical storm that had so badly affected many eclipse chasers going after the 2002 Mexican annular. Even the day before the eclipse. when the skies had been dark blue and cloud-free for a change, the BOLAM weather model - accessed from an internet café in Midoun on the island of Jerba - had predicted new cloud bands over the eclipse zone.

The morning of October 3rd had dawned cloudy indeed over Jerba, but in the past few days, the conditions had often been somewhat better in the southern mainland and later in the morning. So off we went with our rental car at 6:22 local time (5:22 UTC), reaching the major logistical center of Medenine by 7:40 - 2 hours and 40 minutes before annularity. By now all the clouds were gone, and some remnant haze was dissolving by the minute while the Sun crept higher. All »plans B, C, D, ...« - based on the dire and apparently incorrect BOLAM model from yesterday - were quickly dropped while we (a couple from Hamburg we were sharing our rental car with, my girl friend and I) were having some coffee and tea in a very typical local café. And indeed this morning's new BOLAM chart - accessed quickly through a nearby internet café - showed hardly any clouds in our region for eclipse time.

While driving from Jerba to Medinine, there had been constant reminders of the upcoming eclipse on the radio (at least on the station in French we were listening to), with contact times given and some warnings about dangers to the eye. This reminded me of an ad I had seen in the French-language La Press de Tunisie on September 29 which had given somewhat misleading figures about the percentage of eclipse to be expected (it was nowhere 100%, of course, and Gabès was even outside the track of annularity) - and had announced that protective glasses could be found at your pharmacist. (Other articles in the French Tunisian press had concentrated on the geometrical circumstances of the eclipse, its rarity - and the fact that Richard West, formerly ESO's spokesman, had come to Tunisia for the event and actually named an asteroid »Tunis« to honor his hosts.)

Walking into the next-best pharmacy, a stack of apparent eclipse glasses was obvious: »ASTROOPTIC« it said on them, that they were made in China, certified in the UK, fulfilled EU norms and were imported by some »AERUS SARL ARIANA TUNISIE«. But when I picked one up and looked through I was shocked: The actual filters were made of bright blue plastic of the kind used in effects lights in theatre - they simply were no solar filters at all! Obviously the Chinese had sold them incredibly stupid and dangerous fakes - and no one in Tunisia had recognized that! In most countries I had travelled to for my - now 19 - full-silhouette eclipses the »eclipse glasses« on sale locally were fine, and in one case (Mexico 1991) they were actually way too dense because panicking authorites had put so many different filters at once into the frames that you could hardly see the uneclipsed noon Sun through them.

The »ASTROOPTIC« trash sold in Tunisia - in pharmacies!!! - in 2005, however, was the first dangerous fake I have ever encountered myself. Even if those »glasses« sold in the Medenine pharmacy were an exception (I wish I had checked in more places, but I at least heard a story of someone getting headaches using locally-bought »eclipse glases«) this incident alone is a true eclipse scandal worthy of a formal investigation, perhaps by the eclipse committee of the IAU. But now was not the time: The first contact had just happened and we had to find the right observing spot. With weather no longer a dominant factor, it was all about distance from the edge of the annularity zone: The closer you get, the more dramatic and prolonged the Baily's Bead effects get and the shorter the phase of the closed ring is (which, most eclipse veterans agree, is rather boring). But if you get too close to the edge of the zone, you lose the ring completely and things get rather hectic, with the Bead-ing of 2nd contact directly merging into the 3rd and the show over rather quickly.

Precise coordinates for the edge had been calculated long ago, but there was still intense debate in the community about the best place to be relative to that thin band, for various tastes. With about an hour to go before annularity we found another group of German observers we had been in contact before: The had just SMS-d us their GPS coordinates and we had then located them with our GPS! Their chosen site at 33° 21' 40.1" N, 10° 33' 11.7" E felt too close to the edge for us, plus there were some low clouds hovering in the North now: Thus we sped south a bit, through Medenine again and finally positioned ourselves - 30 minutes before annularity - just south of the city next to the road to Tataouine. If the clouds would move south, we could try to outrun them by diving deeper into the zone of annularity. They didn't, though, and neither did we.

At our spot at 33° 17' 45.9" N 10° 28' 29.9" E we would be somewhat inside the zone on the one hand - with a guaranteed closed ring, providing for some spacing between the two contacts - but also two phases of Beads and possible chromospheric windows much prolonged as compared to the central line. Quickly the tripods and telephoto lenses were set up, plus two video cameras that were only second thoughts: While the image quality is much inferior to the still photographs, they still managed to capture some of the dynamics of the eclipse plus the clicks of the camera and some commentary. While we were preparing ourselves - and the Sun shrinking to a crescent with the two horns closing in on each other with increasing speed - quite often local motorists would stop and visit us: They were all very friendly and interested in our setups, and one even started a debate on where the best observing location would be; at least the concept of a central line had apparently been communicated in the Tunisian media.

During the precious moments of annularity we were alone, though, while cars and trucks were moving by as if nothing unusual was going on. Other than our inconspicious colleagues which we had only found thanks to GPS we had not seen one other obvious eclipse observer, neither foreign nor local, and while there had been coverage in the media - and the sale of the dangerous non-filters - the eclipse didn't seem to have much of an impact on the country (other than that the new moon it marked would start Ramadan. Things were very different in Spain, according to some papers I bought on the way home, with huge crowds in the streets and public life »paralyzed« by the eclipse, as one headline put it; whether the Algerians, Libyans, Sudanese etc. who were also hit by the track of annularity made more of it, has been hard to find out so far.

The appearance and rapid changes of the Baily's Beads between the crescent horns were easy to follow in the view finder of the Canon camera with the Russentonne Maksutov, as long as one layer of Rettungsfolie was on: This was what we had come to see, for the flickering of sunlight through the lunar valleys is actually much more dynamic - and prettier to look at - than the similar effect when a total eclipse is imminent. In contrast to the latter it is not possible to look at the show directly with the unprotected eye, however, and the ring phase is not observable directly, too: The huge amount of photosphere left uncovered by the Moon is way too bright to look at without a real solar filter. The first phase of Beads lasted approximately 10 seconds (judging from the crappy videos and the audio commentary), the ring stayed closed for 1 minute and 50 to 55 seconds (time to catch your breath and check the equipment - I used it e.g. to refocus the camera), and the second Beads phase was even longer at 15 to 25 seconds.

Then it was over: After three consecutive successes with annular eclipses in 1992, 1994 and 1999 and another three failures (of seeing the annulus in the sky, that is; partial phases were always caught, and the trips were great) in 2001, 2002 and 2003, annular # 7 had been a full success again. That is as far as getting to about the right spot (well, perhaps one could have dared to get even closer to the interior limit of the graze zone, for just 30 seconds of annularity) in perfect weather - with outstanding atmospheric seeing - and without obvious technical breakdowns. But only when I held my precious photos in hands exactly 50 hours later back in Germany, the success was really complete ...

The trip to Tunisia had lasted only one week, but much sightseeing and many interesting encounters with a culture both deeply Arabic and influenced by France in many ways could be packed into it. To get to southern Tunisia conveniently and on the cheap we had actually booked a package tour with flight from/to Düsseldorf, transfer and half-board stay at a hotel on the Plage de la Seguia on Jerba's SE coast - later we had found many strange remarks on that very hotel, but in the end those who wrote in favor of it mainly got it right: The service worked, the food was gorgeous, and there was indeed free (and local!) wine every evening. For four days we had booked a rental car and did 1307 km with it: Driving in this part of the world is actually fun (except in the crowded town centers), and the gas is cheap (compared to Germany; it costs some 60 Euro-cents per liter).

Jerba itself is very flat, mainly a heap of sand in the ocean (actually a part of the mainland that broke off), though filled with 500,000 or so date palm trees and very characteristic white »Menzel« houses; the many hotels on the coast often try to mimick that style and some actually succeed. There is a bit of Roman archaeology here (a major excavation but also fascinating building fragments just lying around near the sea, if you know where to look); a long dam connected Jerba with the mainland is even built on Roman foundations. The landscape on the mainland is at first dominated by agriculture, too, but wait until you get to the mountains in the west beyond Medenine or to the Sahara that dominates the southern third of Tunisia! Here the boredom of the plains all of a sudden turns into a dramatically different world (often used for movie productions), with mountain villages, cave houses and ksars: The latter are often huge old storage facilities now either preserved as historical sites - or integrated into village life.

Heading south it's either the Sahara that beckons, with great sand dunes and lots of camels, waiting for customers (we declined) or ranging freely in the desert. The warning signs for them are great fun for (German-speaking) astronomers, because they often say »Vorsicht, Dromedar-Durchgang«, with Durchgang being a German word rarely used other than for transit in the astronomical sense (as in »Venusdurchgang« = transit of Venus). The brand- new road between Douz and Matmata is particularly appealing. And another new road let us through the Sebkret el Melah, a salt lake with spectacular salt formations and unearthly colors. The cities sprinkled throughout that varied and fascinating landscape are full of nice and often helpful people, and even exotic wishes can be fulfilled: I needed a map and a ruler to plot the graze zone for our planning and got it easily - and when I wanted some cardboard for building a holder for the Rettungsfolie in front of the Russentonne, a friendly shop owner in Midoun actually emptied a box full of matches and gave it to me for free. Even when the Tunisians didn't get much out of their eclipse, they surely help us strange visitors to get our fix ...

Tuesday,
Sep. 27
Early morning flight from Düsseldorf, Germany, to Jerba, Tunisia; apparently both hand and checked luggage is X- rayed on arrival, and the Russentonne catches someone's attention. After actually looking through it, the customs agent seems satisfied, though. Bus transfer to the huge Djerba Melia Menzel hotel and getting some rest.
Wednesday,
Sep. 28
Meeting our travel companions from Hamburg and exchanging anecdotes from our travel so far - they had some trouble bringing a GPS receiver into the country because they faxed in the correct form before the journey; those who hadn't weren't bothered - and from world of planetaria, where we have much in common.
Thursday,
Sep. 29
Taxi trip to Houmt Souk, the capital of Jerba - the celebrated souk (=market) turns out to be way too tourist-oriented but I get the ruler I need in a real shop nearby. For the first time sunset can be »observed« from the hotel roof; with a nice cat conveniently posing as foreground. The rental car is delivered in the evening, with much buerocracy, but everything is o.k.
Friday,
Sep. 30
First big »expedition« to the mainland: Visit to the ksar in Medenine, on to Beni Kheddache in the mountains and then to the marvellous Ksar El Hallouf (»Castle of the Pigs«) - deep in the mountains and potentially a great site for an exotic star party, we feel. On the way back »inofficial« visit to the already closed Roman ruins of Gightis, until a guardian throws us out; return to Jerba with a ferry. Sunset in the interior of the island: With so many date palms, there is always one you can use as foreground!
Saturday,
Oct. 1
Second big expedition, this time via Gabès and Kebili to Douz: At noon this »gateway to the Sahara« is all but deserted, but many tour buses will soon arrive (as dozens of camel guys already are) - time to leave after visiting the huge date palm forest. Spectacular road - with one impressive dust devil nearby and many free-ranging camels - to Matmata where famous cave dwellings beckon: We visit the very one where Luke's home in the Star Wars movies was located and one that is still in use (or at least acts as a living museum - hard to tell). Spectacular mountain scenery with flocks of sheep and goats being let home at sunset; this time there is a huge trafic jam in front of the ferry, but the view of the Milky Way overhead makes up for the inconvenience (and interesting food being sold to the waiting motorists, too). Navigating home to the hotel through the island interior with the help of the stars and rising Mars in particular ...
Sunday,
Oct. 2
On the day before the eclipse - with gorgeous weather! - a lengthy odyssey (fitting for an island where according to the legend Odysseus did visit :-) on the search for an internet café to get a weather update; it is eventually found in Midoun, the 2nd-largest town on Jerba. Also many local newspapers in Arabic and French with eclipse stories can be bought as well as the latest Ciel et Espace from France - with the eclipse on the cover and even two (real!) eclipse glasses included. This is also the shop where I get my cardboard box. In the afternoon visit to another group of German eclipse chasers near Zarzis; I know there are some more around, but no contact is established. On the way back evening visit to Roman remains near El Kantara; a truly strange scenery. Sunset from the hotel used for trying out high-magnification video; the monochromatic nature of the red setting Sun masks a severe chromatic problem, though, that will make the eclipse video, hmm, colorful ...
Monday,
Oct. 3 -
Eclipse Day!
After leaving the hotel very early and then sitting around in Medenine a while, the eclipse is observed just south of the city with great success. Continuing the road to Tatahouine onwards soon after 3rd contact, a visit to the incredibly big Ksar Oued Soltane follows, the southernmost point of your journey. The landscape is just as a European would imagine Northern Africa at the edge of the Sahara - probably because many movies were shot in this area, e.g. The English Patient. Only the people are stranger - and poorer - than further north (and it seems to be cool for small boys to throw stones at cars with foreigners). Leaving this fascinating but somewhat scary world we see a surprising road sign to Jerba - apparently yet another new road. The 115 indeed leads us (via the salt lake) back to Zarzis for a little post-eclipse party with the other German group; then it's back to Jerba.
Tuesday,
Oct. 4
Again an early-morning return flight to Düsseldorf, this time with an interruption in Monastir - all passengers have to leave the plane while it is being cleaned; at first we stand around on the taxiway, then a bus comes but drops us off in the wrong place, and when the transit area is finally found, we have to get back aboard the plane immediately. End of story, but only for ½ year: Then a long total eclipse will hit the general area again (with the central lines actually crossing each other in the Libyan desert) ...

Links to more stories from this eclipse can be found in the header of the Cosmic Mirror # 292 and in a list by the Reisebüro in der Südstadt! Pictures of the chromosphere in particular - though with fewer or no superimposed beads - and sometimes also prominences were obtained by Birkner, Ewers, Kampschulte, G�hrken, van Kerkhof, Williams and Richardsen. And NightSky had long report from Tunisia.

First posted - already with the eclipse pictures - on Oct. 6, links added Oct. 10 and 13, times.html added Nov. 12, tunkarte.jpg added Nov. 14, 2005, more links added March 5, 2006.