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 daytime darkness for a brief period and allowing observers to see a range of unusual natural phenomena. The most spectacular sight is a total solar eclipse, when the moon completely covers the Sun, with crimson prominences licking around the jet-black disk and streamers of the solar corona reaching far out into space.
The orbit of the Moon
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. Whilst it is not possible to detect this difference in size without accurate instruments, 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 the longer the duration of the eclipse.
The path of the shadow
A total eclipse of the Sun is only visible from a very small strip on the Earth's surface, occurring once every eighteen months or so. Unless you are exceptionally lucky, as the shadow can pass over any part of the Earth, you are almost certainly going to need to travel away from home to see this event. For most people travelling to see an eclipse, this is a large part of the attraction as nature has set the destination and the journey is usually a discovery of unknown places and new people.
Astro Trails current eclipse projects can be viewed here