Similitudes

Watching a lunar eclipse is like many things. It is like reading Hamlet and understanding every word, every cadence. It is like having a candlelit dinner at home. It is like watching your favorite movie. But even more suggestive is what a lunar eclipse is not like. It is not like a total solar eclipse, with its massive emotional buildup, brief exultation at totality, then a partial letdown after. An eclipse of the Moon is more like a two-hour long massage, pure relaxation followed by joy at the event's having taken place over your head. So long as the weather is clear, you really can't go wrong with a lunar eclipse.

In the spring of 1997, as Wendee and I were preparing for our March 15 wedding, we faced the problem of our on-campus ceremony being marred or postponed by crowds attending a basketball NCAA playoff game. We telephoned Mike Terenzoni at the Flandrau Science Center, the place we had chosen for our nuptials. “What about changing it to one week later, March 23?” we asked. “Not then,” his answer came. That's Hale–Bopp.”

I considered the impact of having a wedding on a night near closest approach to the Earth of the great comet of 1997. “Actually,” I explained, “Hale–Bopp will be bright for so long that it really doesn't matter.” But Michael was already looking at his calendar. “And,” he added, “there's a lunar eclipse that night.

Of the many eclipses of the Moon that I have enjoyed, none can approach, or will likely ever come within reach of the unbelievable blackness of the eclipse of December 30, 1963. That eclipse had the Moon pushing its way through an atmosphere clouded with dust from a recent volcanic eruption. Constantine Papacosmas, an experienced observer who saw it with friends, barely saw the Moon at all, and then only faintly through binoculars. He estimated that the eclipsed Moon was no brighter than a fifth-magnitude star. From where I was, finding the Moon in a city sky was almost impossible. I recall enjoying the clear, bitterly cold night, then rushing indoors to sit atop an electric heater.

Solar eclipses

In the next 20 years, eclipses of the Sun will cross a variety of paths over the world. Here is a list of what's in store (total eclipses are in bold).

Remember: Do not ever look at the Sun without proper protection for your eyes. Permanent blindness can result from even a quick look. Normally the Sun is so bright that you are forced to squint, then quickly turn away, as a built-in protection. But during an eclipse, when the Sun is partly obscured by the Moon, you are tempted to look at it longer and more intensely. The Sun's ultraviolet rays can actually burn a hole in your retina, resulting in permanent, partial blindness. A welder's glass (No. 14 strength), or specialized eclipse glasses that are available from telescope stores, will block enough of the Sun's ultraviolet rays to make it safe to look through.

During the total phase of a solar eclipse, when the Sun is completely covered by the Moon, it is completely safe to look at the Sun. Protection must be in force again, however, right after the end of totality.

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.

A total eclipse of the Sun is one of the most thrilling events that Nature has to offer. That one thought is enough motivation to travel the length and breadth of the world to see one. But, in the past, astronomers learned amazing things about our solar neighborhood from watching one. In the second millennium BCE, according to the Shu Ching, the Chinese observed eclipses and became so proficient in predicting them that two of their astronomers, Hsi and Ho, were put to death after they failed to predict one. This story is apocryphal. It is unlikely that astronomers were really able to predict eclipses accurately that long ago. By the sixth century BCE the Chaldeans might have been able to make rough predictions of eclipses.

Any solar eclipse – even the tiniest of partial eclipses – is an event worth watching. I believe that Shakespeare and his colleagues, in a little studied, probably multi-authored play Edward III, were describing a total eclipse even though this was years before the great solar eclipse of 1605. (The full quote opens Chapter 5.) Although it is highly unlikely that Shakespeare ever witnessed a total eclipse of the Sun, he probably heard or read reports about them from those who had. Also, he had the opportunity to witness several partial eclipses from London, including one on July 31, 1590, during which half the Sun was covered by the Moon at maximum. There were other, shallower ones, like the sunset eclipse on August 11, 1589. More important, the great writer's fertile imagination would have allowed him to imagine what a solar eclipse, continued to totality, might have looked like. It is this sense of imagination and dreaming that leads me to believe that he had an eclipse in mind when he wrote (if he wrote) the lines that begin the next chapter; this was a play of multiple authorship.

In July 1990 Steve Edberg and I drove for several hours along back roads to a spot in Northern California where we watched the Sun begin to set.

Whether day ended 400 years ago in Sir John Davies's time, or as it does today, the night sky that has attracted people for thousands of years begins another nightly show. For committed astronomers, amateur or professional, that darkening sky is all that is needed to get our juices flowing. Others require a little more, not just a static display that changes subtly from hour to hour, but something startling, something that crashes upon the celestial stage. A bright meteor, or an eclipse, can spark a lifelong interest in the sky. Eclipses are predictable, and there is usually nothing subtle about them. We can take the experience of an eclipse and put it into a bottle of fond memories. Eclipses show that the sky does change, that the sky is the show that never ends. Eclipses can inspire, and that is why I wrote this guide to getting the most from them.

An eclipse journey

Eclipses are so interesting that some people travel the world to catch them. My wife Wendee and I did this quite literally in late 2003, when we flew across the Atlantic from our home near Tucson, Arizona.

Because eclipses of the Moon are so much more relaxing than those of the Sun, it can be fun to set up your camera and photograph the progress of one. The first thing to recall about night photography involving the sky is: never ever use a flash. If you are trying to photograph the Moon, which averages 240,000 miles distance, it is useless to expect that a small flash attached to a point-and-shoot camera would light up an object so far away. That said, I proudly present a picture (overleaf) that I took of a full Moon taken with a flash, which did not light up the Moon but did fill in the earthly foreground.

The other thing to remember is that eye protection is unnecessary for lunar eclipses. They are perfectly safe to watch and enjoy. The full moon is dazzlingly bright through a telescope, but nowhere near bright enough to damage your eyes. I have taken good pictures of an eclipse just by holding a camera next to the eyepiece of a telescope – a low-power eyepiece, preferably – and snapping some shots.

Using point-and-shoot cameras

The cheapest camera that you can buy these days is a point-and-shoot camera. These little wonders are actually pretty sophisticated. All but the cheapest have built-in light meters that set the exposure automatically.

I love asking children what happens when the Moon gets in between the Sun and the Earth. The answer, of course, is a solar eclipse. And what happens when the Earth gets in between the Moon and the Sun. As the Earth's shadow strikes the Moon, we have a lunar eclipse. So what, I finally ask, happens when the Sun gets between the Earth and the Moon? I love their expressions as they start to think of the absurdity of that ever happening. It is a question that makes them think about the wonderful dance of worlds that results in these eclipses. The most important thing to remember about eclipses, then, is not their cause, but their beauty. For lunar eclipses, our thoughts can ruminate on how the shadow of our troubled Earth can move so gracefully across the Moon, as Thomas Hardy noted after the eclipse of 1903, and whose poem is printed at the opening of the chapter on total lunar eclipses (p. 112).

I think that this is the right way to think of a lunar eclipse, because the shadow that falls upon the Moon is that of the Earth – all the Earth – from its continents and oceans to its people and nations.

After more than half a century of observing, I thought I had seen it all – total solar eclipses, penumbral lunar eclipses, occultations of stars by the Moon, and transits, but as yet I had never seen a planet occulted by the Moon. So it goes without question that I was thrilled at the prospect of seeing the waning crescent Moon swing over Venus in the predawn sky on Wednesday morning, April 22, 2009. While the occultation was visible from much of North America, it was only in Arizona and parts of other surrounding states, where Wendee and I live, that the ingress would take place in a completely dark sky. It would be a highlight of the International Year of Astronomy, which reached its peak during 2009.

So with the best of intentions, and the chance to add something new and different to my observing accomplishments, I set my alarm for 4:30 am (Oh-dark thirty, as an airline pilot friend once commented). But I stepped outside to see the first cloudy sky in several days. I walked to the observatory to go through the motions. However, as my eyes became more dark-adapted, I could see that there was a small break in the clouds toward the east.

Here is a list of the 77 times that I've been touched by the wandering shadows of Earth and Moon. This personal canon of eclipses begins with an almost clouded out partial solar eclipse on October 2, 1959. On March 12, 1960, my mother promised me a lunar eclipse, but since I do not recall seeing it, that event might have clouded out also. (The eclipses that are lettered, not numbered, are events I planned to see but did not see.) However, according to this canon, I did see that eclipse – perhaps not in 1960, but when lunar saros 122 repeated itself two cycles later on April 4, 1996. (See below.)

My first total solar eclipse, on July 20, 1963, was a part of saros 145. I saw it again on August 11, 1999. When the cycles of the solar system converge again, I hope to enjoy the eclipse one more time, when it crosses the United States on August 21, 2017.

What is the difference between a total eclipse of the Sun and anything else Nature has to offer? All the difference in the world. A total solar eclipse, it has been said, is Nature's grandest offering. Nothing – not even for me the discovery of a comet – can approach the ecstasy that accompanies the sight of the Sun vanishing and being replaced by a jeweled crown. It's not just the appearance of the Sun transformed that does it; it appears that the rapidly dimming crescent Sun, increasingly covered by the Moon, provides a real-time dynamic event that is truly breathtaking.

The eclipse of 1918 … and of 2008

Of all the eclipses I have seen, for now I'd like to focus on just one – the eclipse of August 1, 2008. It was a repeat of the total eclipse that occurred 90 years earlier, on June 1, 1918. In a sense totality never ended that day long ago. Of course, totality could never last more than seven minutes and a few seconds for any eclipse, let alone a century, but in the minds of those who watch, the experience never ends. There is really no other way to write it; a total eclipse of the Sun is likely Nature's most incredible spectacle.