Updated: Aug 2
The total solar eclipse of 2020 December 14 started at sunrise in the middle of the Pacific Ocean, fortuitously reached its maximum duration of 2m 10s as it swept across a thin strip of south America and ended at sunset off the coast of Namibia. The centre of the umbral shadow swept across Chile and Argentina in less than 19 minutes and these were the only two countries where observation from land was possible. The weather prospects were generally better to the east of the Andes and so Astro Trails selected an observation site at Fortin Nogueira near Piedra del Aguila, in Neuquen province, Argentina. At our site we would have an eclipse duration of around 2m 6s.
This eclipse would be very different to the one that we saw from Argentina in 2019. That eclipse was almost at sunset in the southern winter, this one was near mid-day with the sun 72º up in the southern summer sky. The main difference though was nothing to do with astronomy, geography or weather. The emergence of the COVID19 virus pandemic resulted in massive restrictions on everyday life around the globe and it had a huge impact on international travel. Countries closed their borders to international visitors and airline schedules were in a constant state of chaos. Astro Trails is a company that is used to organising eclipse trips in difficult circumstances but this was on a different level entirely. Travel to Chile and Argentina was just not possible through most of the year and many other groups decided that the effort and risks were too great and so they dropped their tours.
Against all the odds Astro Trails, and their local agents Eurotur, managed to arrange special access for a small group of 40 people to visit Argentina and to travel to the eclipse. We were the privileged few who would be lucky enough to travel to the path of totality in a very strange year. A lot of paperwork was required: we had PCR tests before flying out and on arrival and we had to abide by a special COVID safe travel protocol but the trip was very well organised and went without a hitch.
My plan was to get images of the eclipse using four cameras which would operate without much input from me during totality. This would let me watch the eclipse with the naked-eye and binoculars and forget about imaging for that critical two minutes. I had a GoPro Hero 6 camera for wide-angle video, this had a wide enough field to get the horizon and sun in at the same time, a Panasonic TM700 camcorder for medium scale video and a Sony A7s camera with a 100mm f/2 lens taking medium-wide field stills through totality. All of these were on fixed tripods and the A7s was pointed to get the starfield west of the Sun where a known comet (C/2020 S3 Erasmus) would be visible around 11º west of the Sun. My final setup was a ZWO ASI183 camera and a 500mm, f/8 Tamron mirror lens on a Star Adventurer equatorial mount. This had a field of view of 1.5º×1.0º with a resolution of 5.5×3.7 k and was capable of taking 7.5 frames per second generating around 70GB of image data through totality. I was hoping to get some good prominence and inner corona images with that.
As eclipse day approached it became apparent that the forecast for our site was pretty good. Cloud was expected in the morning but this would clear around noon, leaving us with a clear sky for totality which was just after 1pm local time (3 hours behind UTC). Other sites to the west, in Chile, were plagued with cloud and rain. The forecast did, however, predict high winds of 50mph or more at eclipse time. These winds are not unusual in Patagonia in the summer but I was worried that they would cause problems by shaking my narrow field camera during the eclipse.
When we arrived at the site a few hours before first contact it became apparent just how windy it was going to be. In the open it was a howling gale but we managed to set up in a horse paddock which was surrounded by tall trees which acted as a very effective wind-break. The howling gale was reduced to just a very blustery wind. Since the Sun was going to be very high in the sky at totality we could all keep tripods very low to the ground and this helped too. The most important thing though was that the sky was completely clear. My equipment set up was straightforward and food and drinks were distributed ahead of first contact so that we were all well relaxed by the time of first contact.
First contact was at 11:45 am local time as the moon rapidly started to cover the sun. There was only one small sunspot on the sun (AR12792) and this was covered up around 15 minutes before second contact. As the sky darkened, Venus, around 24º to the left of the sun, was clearly visible around 5 minutes before second contact.
With a few minutes to go until second contact the wind gusts became even stronger and the previously clear sky was suddenly full of very fast-moving low clouds. One of these passed over the sun at the critical moment of second contact but it was thin enough to allow us to see the diamond ring and a beautiful multi-coloured corona on the clouds. We also saw shadow bands on the ground and projected onto the thin clouds above us. Even through the thin cloud, totality was a gorgeous sight with an extensive corona visible to the naked eye and multiple prominences visible in binoculars.
Thirty seconds after second contact the sun came back into clear sky where it remained for the rest of totality. The corona was now visible in all its glory showing a typical solar minimum shape with long, equatorial streamers and prominent polar brushes. Mercury was visible 3º to the left of the sun and Jupiter and Saturn approaching their conjunction were visible 36º to the right of the sun.
In binoculars there were multiple prominences and at least four were easy to see as soon as totality was underway. The moon was moving from left to right and so, as the large prominences on the right hand (eastern) limb of the sun were covered up the ones on the left became more prominent. A long row of low prominences near the third contact position made me think that the eclipse was almost over since I thought that they were the chromosphere. In fact, they appeared more than a minute before the third contact diamond ring and they became more and more prominent as the moon slowly uncovered them.
The diamond ring when it came was spectacular and was a fitting end to a beautiful eclipse. Very few eclipse chasers were lucky enough to be in the right place to see this one and I felt very privileged to be part of this trip. We all celebrated with champagne after the eclipse as we watched the horses re-occupy their paddock and start to demolish our hay bales. A few weeks earlier most of us thought that it was unlikely that we would make it to Argentina, but the persistence of Julie and Brian and the local expertise of Eurotur managed to pull this trip off against all the odds.
Looking at my wide field images after the eclipse I had managed to record two comets close to the sun during totality. C/2020 S3 (Erasmus) was there in its expected position along with a sungrazer comet C/2020 X3 (SOHO) which had been discovered the day before. I believe that this may be the first time that two comets were imaged at the same totality. Andreas Möller, who was also on our tour, also picked up this sungrazer in his excellent corona images and he was mentioned in a NASA press release:
Miloslav Druckmuller has processed Andreas' corona images which can be seen here:
The day after the eclipse those of us in Bariloche had the opportunity to travel out of the town to a very dark spot for some stargazing. As we arrived at the observing site, we had a great view of the crescent moon, only 33 hours after we had last seen it in front of the sun. To the right of the moon was the close pairing of Jupiter and Saturn. As dusk turned to night, we had a great view of the southern summer sky including the Southern Cross low to the south and the two Magellanic clouds high above the southern pole. A fitting end to a wonderful and extraordinary trip.
Our thanks to Nick James for this report - Nick travels regularly with Astro Trails as one of our tour leaders and expert lecturers. A version of the report also appears in the Journal of the British Astronomical Association - TSE2020 British Astronomical Association Journal report