Ring of Fire: Annular Eclipse over Spain, 3 October 2005


Introduction

Following the disappointment of being clouded out in the Orkney Islands two and a half years earlier, now comes an eclipse where the weather did us proud, with scarcely a cloud in the sky. Well, we were in Oliva, on the Mediterranean coast of Spain coast between Valencia and Alicante, and this area had the best weather prospects of anywhere in Europe to see the eclipse.

The roof terrace of the house of a friend proved to be the perfect location to see the entire annular eclipse. Oliva was nearly on the centre line of the eclipse track, and the Moon was predicted to be entirely on the face of the Sun for 4 minutes 14 seconds.

An annular eclipse occurs when the Moon crosses the Sun but is too far away from the Earth to cover it completely. Therefore, at maximum eclipse you see the sun as a ring of light (or annulus) surrounding the silhouette of the moon - this is the Ring of Fire. However, eclipse glasses or filters are required at all times because some of the Sun's bright surface, or photosphere, is always visible, so none of the faint corona ever becomes visible as in a true total eclipse. Nevertheless there was still plenty to enjoy, as my account below describes...


The Experience

I initially had my doubts as to whether our rooftop location would be adequate to catch the start of the eclipse because I wasn't sure whether the Sun would clear a nearby house in time...

Oliva skyline
Looking East from our rooftop terrace at 9am, 40 minutes before the start of the eclipse.

Having arrived in town only the evening before, it had not been possible to do a dry run, but in the event there was nothing to worry about. Even the clouds that initially lay to the East disappeared almost completely by the time the eclipse started so we enjoyed an uninterrupted view of the whole event.

We set up our equipment on the roof, Bruce with a Fuji Finepix with a solar viewer taped over the lens at maximum zoom, Mark with a Canon EOS digital with a mylar screen over a telephoto lens, and myself with my Minolta Dimage 7 attached to a Helios 80mm f/5 telescope. First contact, when the first small bite starts to appear on the edge of the Sun, was detected at around 0741 (9.41 am local time) 1 hour 19 minutes before annularity. Because the Moon was near apogee (i.e. its maximum distance from Earth), not only would it be too small to cover the Sun completely, but also it would be travelling relatively slowly so the whole eclipse would take longer than normal. As a rough guide you can reckon on an eclipse lasting around two hours in total - here it lasted 2 hours 40 minutes. Conversely, a fortnight earlier when the Moon was opposite the Sun in the sky, it was at perigee (i.e. at minimum distance from Earth) so appeared slightly larger than the Sun as this picture (taken by Mark on 14 Sept 2005) reveals.

As we watched and recorded the Moon's progress onto the Sun we were joined by other interested friends, who used the additional viewers I had brought with me. Rumour had it that the local Spanish had been told that it was OK to view with sunglasses alone as many places had run out of eclipse viewers. The next day Valencia newspapers reported 5 people admitted to hospital with eye problems. I hope that no permanent damage will result from this bad advice, but it shows that you must be careful.

We also successfully projected the Sun onto walls and other buildings with a small mirror to show the changing shape of the Sun as the Moon advanced. Most successful of all though was using small holes made by a satellite dish on the roof, and made by our own fingers and heads, where casting an image onto a neighbouring wall made some very curious shapes indeed.

As annularity approached a noticeable chill developed in the air, and the sky, now virtually free of clouds, grew darker, much like what you see when looking out of an aircraft window at altitude.

View NW across Oliva at 10.05 CED
Looking North West from our rooftop terrace at 10.05am (0805UT), 25 minutes into the eclipse. At this stage the Sun was only about 30% eclipsed so no change in light level or temperature was evident yet. Exposure: 1/1000s @ f/4.5

Rooftop gathering at 1043CED
Rooftop gathering. The time is now 10.43am (0843UT), an hour into the eclipse, and 17 minutes before the start of annularity. By now the Sun was 75% eclipsed, with the sky showing a noticeable darkening (compare with the previous picture) and temperature levels starting to fall. Exposure: 1/1000s @ f/3.5 (65% more exposure than the previous shot)

Pinhole images 3 minutes before annularity
A satellite dish in the corner of the terrace proved the ideal way of monitoring the progress of the eclipse without any optical aid at all. Where sunlight passed through a small hole an inverted image of the Sun was formed on a wall of a neighbouring house. This was the apearance at 10.56am, (0856UT), just 3 minutes before the start of annularity. Our own heads and fingers acted in the same way, creating the outline of some alien lifeforms!

Pinhole images during annularity
4 minutes later the crescents had turned into bull's eyes as the Moon moved completely onto the Sun. Even edges produce a sort of half image and where two met near the lower left corner of the dish an interesting cross pattern was produced.

Here at 11.14am (0914UT), 11 minutes after the end of annularity, the crescents were back. However, they were now turned round so the frowns became smiles and a different sort of alien cast its shadow onto the wall. This is an interesting demonstration of the pinhole effect - when an light is shone onto a surface at a sufficient distance in relation to the size of the hole, the result is a true image rather than simply an outline of the shape of the hole.

As the Moon continued to move off the Sun the light levels and temperature were quickly restored to what you would expect for a fine Spanish morning.

We later learned that in the Pyrenees and southern France, where the eclipse was about 85% partial, that there was no noticeable darkening of the sky, but the temperature fell far enough for it to snow in Andorra and on the high Pyrenean peaks, practically unheard of this early in the autumn. Passing through Andorra on our return to France snow still remained beside the road above about 1300m altitude - there may have been more but this was all we could see because it was dark by the time we got there. A visit to Barrage de Soulcem the following day, in daylight, indeed revealed snowcapped peaks.

Eclipse snow: even on 6th October, 3 days later, snow still remained on the peaks south of Barrage de Soulcem, south west of Tarascon in the eastern Pyrenees. The further ridge has an extensive covering, while the nearer peak still has a little snow on its north facing slope.


View through the Lens

Bruce's pictures, taken with a solar viewer taped onto a telephoto lens, give a good impression of the visual appearance of the eclipse. This animation using frames at approximately 15 minute intervals (more frequent near and during annularity) shows in a few seconds what we saw over two and a half hours. Time lapse through eclipse viewer

This view is orientated exactly as we saw it. The Moon moves almost vertically from top to bottom, which is explained by a number of factors all working to increase the angle...

The sum of these angles is 79 degrees, only 11 degrees off the vertical, so it is easy to see why the Moon appeared to move almost straight down from top to bottom.

My telescopic setup produced larger views than a telephoto lens alone, and by using an equatorial drive to track the Sun's movement, the pictures are aligned with respect to the sky rather than the ground. North is straight up and East is due left. Therefore the Moon enters from the upper right and departs at lower left.

This picture shows the view 6 minutes after First Contact, when the Moon first makes a bite out of the side of the Sun. The Sun is completely devoid of any sunspots, often the case when it is near the minimum of the Solar Cycle as it is at the moment. However, a little over two weeks earlier a large naked eye sunspot was visible, but by the time of the eclipse it has rotated out of view, carried round by the Sun's 30 day rotation period.

I deliberately kept the exposure of this and similar shots at a level to stop the Sun being too bright - the darkening towards the edge of the disk is a genuine effect caused by light from the surface of the Sun being dimmed by having to pass through the Sun's own atmosphere. It helps to give a 3-D appearance to the scene.

This and all the other brownish pictures taken through the Orion filter have, except where indicated, been reduced to 1/3 of their original size for quick loading and ease of viewing.

Eclipse at 0748UT

The Moon has now reached a little over half way across the Sun. However, the shape of the Moon means that well over half the Sun is still visble, so there is no noticeable reduction in light levels at this stage. Eclipse at 0826UT

A little over an hour after First Contact the Moon had moved 85% of the way across the Sun. Light levels were beginning to fall and it was now becoming evident that the Moon's diameter was less than than of the Sun, so the eclipse would be annular. Of course, we knew this was true, but it was interesting to note at what stage it would become apparent.

On clearer shots you can also see that the Moon is not a perfect circle but that the edge is slightly jagged. This is caused by mountains and craters being seeing edge on at the very edge (or "limb") of the Moon.

The photo below is a full size view of the lower part of the one at right, and shows the uneven topography. Later, this unevenness will cause a phenomenon called Bailey's Beads. Note that the pinkish tinge to the Sun by the edge of the Moon is an artefact of the unsteady air and the imaging system, and is not the result of a lunar atmosphere!

Eclipse at 0850UT

Uneven limb profile of the Moon at 0850UT

10 minutes later the Moon was on the verge of moving completely onto the Sun - Second Contact. By now, it was abundantly clear that the Moon was smaller than the Sun.

The slight irregularity on the right arm of the crescent Sun is the result of lunar topography of the sort mentioned above. This is Bailey's Beads, where with naked eye viewers it seemed that the edge of the Sun had momentarily broken into individual beads of light - this phenomenon lasted only a few seconds and was better photographed at Third Contact.

Second Contact

Annularity lasted a little over 4 minutes, and the picture at right shows, we were practically on the centre line so the Moon created a perfect bull's eye at mid eclipse. The central track passed about 3km south of Oliva and on the central track at this point the duration of the eclipse was calculated to be 4 minutes 14 seconds.

Careful inspection of Mark's photos, which he took every few seconds at the critical moments, reveal that annularity lasted from 08:59:52 to 09:04:04, taking the times from the maximum appearance of the Bailey's Beads. While the absolute times might be out by a few seconds, the duration is reasonably estimated as 4 minutes 12 seconds - the missing 2 seconds is explained by us being about 3km from the true centre line.

Click the picture or here for an alternative view taken 30 seconds later through the Helios / Orion setup as for the pictures above.

This and all the other blueish pictures taken through the mylar filter have been reduced to 1/2 of their original size for quick loading and ease of viewing.

Maximum Eclipse

Third contact was the point at which the Moon starts to leave the face of the Sun. When the leading edge of the Moon reaches the edge of the Sun, Bailey's Beads formed again for a few seconds, caused by the last vestiges of sunlight streaming through valleys and depressions on the Moon's surface.

This enhanced picture, timed at 09:04:04, shows the effect quite nicely, but the irregularities made difficult to judge the exact moment of Third Contact, when annularity ended.

3rd Contact with Bailey's Beads

After Third contact the Moon continued to leave the Sun, uncovering it at the same rate at which it had covered it in the build up to annularity. Eclipse ar 0912UT

80 minutes after the end of annularity the Sun is almost completely uncovered again and the Moon will leave it completely (Fourth Contact) at 10:29UT. Eclipse at 1024UT


Conclusion

This was the first annular eclipse any of us had seen, and with a clear view in a pleasant location ranks as a complete success. While it lacked the splendour of seeing the corona and other effects that occur during a Total Eclipse, it was still worth the travel to Spain to see it for the first time.

Here is a selection of links to details and other pictures of this eclipse...

British Astronomical Association eclipse gallery
Mr Eclipse (Fred Espenak) track, timing and weather predictions
Space Weather Solar Eclipse Gallery


31 May 2003 Solar Eclipse Home 29 March 2006


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