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A Total Solar Eclipse

An eclipse of the Sun occurs when the orbit of the Moon passes in front of the Sun as seen from the Earth. The shadow of the Moon follows a narrow path on the surface of the Earth, bringing darkness for a brief period during the day and allowing observers to see a range of unusual natural phenomena. A total solar eclipse is when the Moon completely covers the Sun, with flames of crimson prominences licking around the jet black disk and bright streamers of the solar corona reaching far out into space.

 

As the Moon goes around the Earth it follows an orbit which is elliptical, appearing very slightly smaller when further out and larger at the closer point. It is not possible to notice this difference in size without measuring instruments but when the Moon is at its closest point it is large enough to completely obscure the disk of the Sun and the closer it is to the Earth, the longer the duration of the eclipse.

The part of the shadow which completely covers the Sun is known as the umbra. The part of the shadow outside the umbra is known as the penumbra and if you are in a location covered by that part you will see a partial solar eclipse.

When the Moon is at a point of its orbit further away from the Earth, the Sun is not completely covered and a very small, bright circle or annulus remains visible. This eclipse is known as an annular eclipse and although it lacks the unique drama of a total, it remains an unusual and interesting event particularly when it is possible to observe the effect of the declining light levels on wildlife.

A total eclipse of the Sun is visible from a very narrow strip on the Earth's surface. Totality lasts for a few minutes and total eclipses occur on average only once every eighteen months or so.

Unless you are exceptionally lucky, you are almost certainly going to have to travel away from home to see this event. Success in observing an eclipse is going to require a mix of competent research and, as far as the weather goes, an element of good luck.

 

Planning for an eclipse expedition involves plotting where the track the shadow cross, then looking at the climate data along the track the time of year of the eclipse.

 

The eclipse will be of shorter duration if your observation point is towards either end of the track, but it is better to sacrifice some duration length in favour of improved prospects of a clear sky. Desert or open dry savanna are a good choice.

Once the location is chosen, it becomes a matter of logistics.  — flights, hotels and such like and then you usually need local transport on the day. The increased interest in viewing an eclipse makes it essential to fix all these matters up a long time in advance.

On the day of the eclipse you will want to get to your observation site in good time before “first contact”, when the edge of the Moon first touches the edge of the Sun. At this stage you will need a special viewer to look at the Sun as a curved 'bite' is taken from one side. Now the tension starts to build as the Moon progressively covers the Sun. The light level goes down, but at the same time your eyes adapt to the gradual changes so the change remains almost unnoticed until the eclipse is well advanced.

The landscape is drained of colour and shadows sharpen as the Sun is reduced to a bright crescent and eventually a single point. Look at the shadows under a tree and you will see the leaves create a thousand small arcs of light. The temperature only drops a degree or two, but there is a sense of chill in the air as the radiant heat from the Sun is cut off. A blue sky has turned to a pale morning grey and bright planets have reappeared.

 

The last couple of minutes before totality race through at top speed as the Moon's shadow hurtles towards you. The Sun is reduced to a single searing point of brightness and as this final point is extinguished, bright beads remain momentarily along the edge as the sunlight shines through the valleys on the Moon. Suddenly the brightness is gone, leaving a jet black disk of the Moon clothed in the flowing robes of the solar corona and surrounded by the delicate red rim of the chromosphere. Crimson licks of prominence's reach out from the rim and as your eyes become accustomed to the dark, the fine structure of the corona becomes visible.

 

There is an unearthly red glow around the horizon and a sense of a large dark shadow looming above. The time of totality ticks by, then a few flickers of bright beads on the edge of the dark disk herald the end of the performance. The burst of light which shocks your dark adjusted vision is the final climax. Always expected but always a surprise: sunlight returns, colour and warmth are restored and everything is back to normal. Until next time...

Eclipse Tracks

 

All eclipse tracks on this site are reproduced from the site constructed and maintained by Xavier Jubier, we acknowledge are grateful to him for his permission to use them. Without doubt he has produced the best web site for detailed information about the tracks of the Moons shadow across the earth’s surface  http://xjubier.free.fr/en/site_pages/SolarEclipsesGoogleEarth.html . 

 

The site is maintained by Xavier Jubier as a free service and provides a vast amount of technical detail about the time and place of eclipses.  Using Google Earth maps as the basis for the geographical locations, the program gives details of exactly what eclipse will be observed at any point on the planet.  If you enjoy maps as much as we do, you will find this site a real treat!

Nick James