When the Moon, during its monthly orbit of the Earth, directly crosses the position of the Sun, the result is a central eclipse. If, at the time of its crossing, the Moon is close enough to us that its angular diameter is greater than that of the Sun, a total eclipse is the result. These are the eclipses we travel around the world to see, and will be the subject of Chapters 7, 8, and 9. But what if the Moon's angular diameter is less than that of the Sun? Then we have what is called an annular eclipse, which we can also call a ring eclipse. During these moments the Moon's black silhouette is surrounded by a brilliant ring of sunlight.

As exciting as an annular eclipse might be, it is still a partial eclipse. Thus, all the strict rules about looking directly at the Sun unfortunately apply. And more: because there appears to be so little sunlight, observers are tempted to look directly at the ring of Sun. Thus, if the annularity lasts more than a few seconds, blindness can result. Therefore, use a filter whenever looking at the Sun during all phases of an annular eclipse.

The annular eclipse of September 2005

Of the several annular eclipses I have seen over the years, none was as inspiring as the October 2, 2005 eclipse in Madrid, Spain.