A solar eclipse occurs when the Moon blocks our view of the Sun. It happens when the Moon is exactly between the Earth and the Sun. By a strange coincidence the Moon is 400 times smaller than the Sun but also 400 times closer. This results in their angular size being about the same, allowing the Moon to completely block the Sun at times.
But the Moon’s orbit is not perfectly circular so sometimes the Moon is farther from the Earth and at other times it is closer. When the Moon is farthest from the Earth it is said to be at apogee. When at apogee during a solar eclipse, the Moon will appear slightly smaller than the Sun and will not cover it completely, and a ring of Sun will remain visible. This is called an annular solar eclipse from the Latin word annulus, meaning ring.
The Moon was at apogee during the annular eclipse of 1994. I took this picture of that event through a special solar filter attached to a telescope. Using such a filter is the only safe way to directly view the Sun. Sun glasses are NOT SAFE to look at the Sun even during an annular eclipse. Never look at the Sun without a proper filter.
As you can see in the picture, the Moon was too small in angular size at apogee to completely cover the Sun. Daylight became ‘very weird’
because most of the sunlight was blocked, but yet it did not get dark. If you look carefully in the picture at the black silhouette of the Moon against the Sun you will notice it is not a smooth circle. The outline of the Moon is
visibly jagged, the result of lunar mountains, craters and valleys seen in
silhouette against the bright surface of the Sun.
The same type of annular eclipse will occur May 20, 2012.
Sadly, it will not be visible if you are located east of Texas, so we will not
be able to see it from Connecticut. But you may hear about the upcoming annular eclipse in a news broadcast, or see pictures of the event displayed on the internet, or perhaps you will be traveling out west. If so, you hopefully now know more about annular solar eclipses and that such an eclipse should only be viewed with a special solar filter.