Acknowledgments

Information on these pages is gleaned from many eclipse sites all over the world.  Thanks to them, and especially to Fred Espenak of the Goddard Space Flight Center.  Fred has unarguably the best eclipse resource on the Internet - be sure to visit his page. Click here to go there in a new window.

Please feel free to e-mail me with any comments or criticisms.  Also, if you want any further information on the eclipses of 2001 & 2002, e-mail me.

All artwork for the Africlipse Logos on this web site are by kind favour of good  friends at Online Advertising,  Click here to e-mail them!

Why and How Eclipses Occur

As the Moon orbits the Earth, it reaches points along its orbit where it is in line with the Sun. When the Moon is between the earth and the Sun, we call this new Moon, and when the earth is between the Sun and Moon, we call this Full Moon.

A Solar eclipse can only occur when it is New Moon, as this is the only position where the Moon is able to block the Sun's light.  Strictly speaking, this is not an eclipse, but an occultation (for total eclipses) or a transit (for annular and partial eclipses)

A Lunar eclipse is only possible when it is Full Moon, as this is the only position where the Moon can pass into the earth's shadow and be eclipsed.

The question naturally arises as to why a Solar eclipse is not seen with every New Moon, and a Lunar eclipse with every Full Moon. The explanation is quite simple, and is because of another highly significant factor on which the occurrence of an eclipse depends.

However, during every lunation, the Moon passes through the ecliptic twice, once on the way down (southwards) and once on the way up (northwards). These points where the Moon's orbits intersects the ecliptic are called the nodes. The node in which the Moon crosses the ecliptic from south to north is the ascending node, and opposite to this lies the node known as the descending node where the Moon crosses the ecliptic from the north to the south.

At least twice a year (sometimes three times a year) the nodes are closely aligned to the straight line between the Sun and the earth, forming a “eclipse window” period when an eclipse is possible.  The alignment of the nodes denotes the ending and beginning of an eclipse season and is 173.3 days apart.  Hence an eclipse year is 346.6 days long.  If an eclipse year begins early in January, the next eclipse window will be in June/July and a further window will occur in late December.  The years 2000 and 2001 have three eclipse windows.

An eclipse window lasts between 30 and 36 days centered on the nodal conjunction with the earth and Sun.  The line between those two nodes rotates once very 18.6 years and this is important for another reason - the Saros cycle.

As mentioned above, the Earth and Moon cast their shadows into space. When a New Moon occurs in the vicinity of a node, it is possible for its shadow to fall onto the Earth, and we will see the Moon eclipsing or partially eclipsing the Sun. When a Full Moon occurs in the vicinity of a node it is possible for the Moon to pass through the shadow of the Earth, and we will see a part or the whole Moon eclipsed by the shadow of the Earth.

The next pages detail the types of shadows cast by the moon and earth, and also detail the types of solar eclipses that occur. A “technical” page on the Saros Cycle is also included.

This Africlipse InfoSite developed, executed and maintained by Peter Tiedt 2001-4.  Please advise me if you link to my site!