The Total Solar Eclipse of June 30, 1973
by George O. Abell
Excerpts from Mercury The Journal of the Astronomical Society of the Pacific
My wife and I boarded the year-old Adventurer at San Juan, Puerto Rico, late in the afternoon of Saturday, June 23, 1973. The ship was one of two charatered by Eclipse Cruises, Inc., to carry more than 2500 passengers into the darkness of the total solar eclipse on June 30. Our sister ship, the Canberra (actually 'big sister', for the Canberra is actually older and larger) had left New York the day before to take up a position at sea in the path of totality somewhat off the Mauritanian coast of West Africa. The Adventurer was to begin with a tour of the Caribbean Islands and then rendezvous with the eclipse in mid-Atlantic
A special feature of Eclipse Cruises, Inc., is their "Science at Sea" program series of lectures by experts representing various fields of science. Our instructional staff included Von Del Chamberlain of Michigan State University, who acquainted passengers with the night sky, and Harvard's Frances Wright, who trained budding navigators to find our position at sea. Expert photographic instruction was provided by William Swann and Richard Madigan, both of Eastman Kodak. Astronaut Russell Schweikart described his own experiences in space. Former astronaut Wally Schirra (now an environmental consultant) discussed our energy and conservation problems, and Ronald Oines, a NASA project director at Oklahoma State University, described the future space programs. Peter Vogt, of the Naval Oceanographic Office, discussed the changing ocean floor and continental drift, and Howell Williams, retired Berkeley Volcanologist, explained the role of vulcanism in changing the face of the earth. Meteorologist Norman Macdonald, from MIT, was responsible for finding the location with the clearest skies for our ship on eclipse morning. James Thomas of the Florida Audubon Society taught birding. Writer Arthur C. Clarke provided much thoughtful insight into what we can expect during the coming century. My own lectures were, of course, on astronomy.
The passengers' interest in these programs seemed to continually increase as June 30 approached, and so did a feeling of excitement and anticipation. There was also an increasing restlessness not quite an apprehension, but concern for the kind of weather we could expect on that great day. One concern to us was the intertropical convergence (ITC) zone, where equatorial trade winds coming together force warm moist air aloft, resulting in extensive cloud condensation. Fortunately, at that time the ITC zone seemed to be limited to within about 7° of the equator, and we were planning to see the eclipse from a latitude between 11°N and 12°N. Still we had been having pretty consistently cloudy weather, especially in the mornings, and for us the eclipse would be total less than an hour and a half after sunrise. In our weather briefing late Friday evening, however, we learned that the satellite data showed that we could expect to be out from under the worst clouds by about midnight, and that only scattered altocumulus lay before us. We knew that the forecast was an accurate one when we went out on deck, and could see alpha and beta Centauri and the Southern Cross shining brightly between scattered clouds.
By this time we began to realize that we might have a better shot at the eclipse than the Canberra stationed along the path of totality nearly 1500 miles east of us. From the outset the Canberra was considered to be the "shoo-in" for seeing the eclipse. Well north of the ITC zone, she expected to be in a region of the Atlantic where the sky is almost always clear. However, to escape a high layer of dust being blown off the Sahara Desert and out over the ocean, our sister ship was steaming westward to take up a position a few hundred miles closer to us than originally planned, in a region that satellite data now showed to have scattered cloudiness. I suppose it is an interesting commentary on human nature that we all received a sort of perverse pleasure from this knowledge. It isn't that we wished bad weather for our colleagues on the Canberra, but if it had to be them or us, we hoped it would be them! By midnight, there was nothing better for most of us to do than retire, try to get a few hours of nervous sleep, and hope for a clear view of the eastern horizon at sunrise. Some, however, stayed up through the night. Among them was Rusty Schweikart and some friends who engaged in an all-night vigil that involved a semi-mock, religious ritual. A few others, including meteorologist Norm Macdonald, stayed awake for more serious reasons.
Several of us on the instructional staff were on the bridge of the ship on eclipse morning. I had the responsibility of making periodic announcements over the public address system concerning the progress of the eclipse, and also to make radio contact with the Canberra. Macdonald was present, albeit bleary-eyed by then, to advise on what maneuver would be appropriate in case of clouds. Sunrise occurred just after 5:30 A.M., but we did not see the sun immediately because the scattered clouds appeared to be much thicker when seen in projection near the horizon, and the eastern horizon was particularly occluded. By 6:00 A.M. however, when first contact took place, the sun was high enough in the sky to be free of the worst of the clouds, and we could by then only hope that during totality one of those scattered tufts of high cumulus would not float by in front of the sun. In another quarter of an hour we decided that our position was about as optimal as we could hope for. The ship was then turned port side toward the east, and all engines were shut down to eliminate vibration. A peaceful quiet fell upon us, and the only motion was a slow easy pitching of the ship with the gentle seas. About the same time we received a message from the Canberra; she was still in the clouds, but because of her location well east of us, first contact would not occur there for another ten minutes or so.
The Adventurer is a modern ship, equipped with the latest inertial-guidance system. It was thus with some surprise (and pleasure) that I saw the navigator take out a sextant just before sunsrise and make a celestial fix. He explained that he just wanted to "make sure." He said he had been having nightmares about stopping at a place where the moon would pass the sun by without covering it in the least! When we did stop, our position was 43° 03'W: 11° 30'N.
By shortly after sunrise the passengers had scattered themselves about the various open spaces on the decks. The decks themselves had been cleared of lounge chairs and other items the night before, and that morning the lifeboats were lowered below deck level so that they would not obscure anyone's view. In place of the familiar furniture there was a forest of camera tripods and telescope mounts. Many passengers had tape recorders to preserve their impressions of the moment. One had a video tape recorded on board. The ship's crew, most of whom had never seen a total solar eclipse, were incredulous during the previous days of the cruise, and many wondered what this odd bunch of people were all excited about. Nevertheless, all who could be were on deck, and those whose duties kept them below were, for the most part, spelled by colleagues for a few minutes during part of totality so that they would not miss the phenomenon altogether. Everyone passengers and crew had been provided with special viewing devices consisting of heavily overexposed film for watching the partial phases. It was amusing to see cabin stewards and cocktail waiters, some of whom had, the night before, joked about the silliness of getting up early to see an eclipse, out there on deck with their viewing devices. All was in readiness. Now, if only those few scattered clouds would just stay away from the sun!
Second contact, i.e. the beginning of the total phase, was to occur about 48 seconds before 7:00 A.M. The predicted duration of totality at our location was 4 minutes and 5 seconds. As the moment approached, the gentle easterly wind increased from about 10 to 15 knots. The morning temperature stopped rising and actually dropped more than a degree centigrade. Then, in the last lingering seconds of the partial phase, the thin remnant of the photosphere disappeared and the full corona burst forth to surround the moon's black disc with streamers of pearly white light. This, of course, was what we had made our journey to see. Fortunately, the sky in front of the sun remained completely clear, save for twenty or thirty seconds when one tiny wisp of a cloud passed by a cloud so thin that the corona shone brightly through it. The sun was then about 18° above the horizon and we could easily see the ghostly reflection of the corona in the eerie, deep green, surface of the ocean. It was all most beautiful.
Some of us on the bridge had dark-adapted one of our eyes by covering it with a surgical eye patch about half an hour before totality. We removed the patches after second contact, and found that with the dark-adapted eye the corona appeared almost twice as large as with the other eye. The sun is approaching its spot minimum, and the corona had the elongated shape characteristic of that period of the solar cycle. In the east-west direction, coronal streamers could be traced to at least a full degree (that is, two solar diameters) in either direction from the limb of the sun. We also found, as some of us did in the 1970 eclipse we watched from Mexico, that we could easily see the corona at least the inner brighter part, for several minutes before and after totality. It was only necessary to eclipse the crescent of the sun not quite covered by the moon with a thumb held at arm's length. I presume that observers just outside the path of totality would be able to similarly view the inner corona.
There were beautiful "diamond rings" at second and third contacts, and despite the stubby shape of the thin crescent of sunlight (because of the moon's relative nearness in this eclipse) we saw Baily's beads flash into view at the sun's western limb at third contact. Several prominences were visible, especially on the east limb. These were best seen just after second and just before third contacts, when the limb of the moon did not extend too far across the chromosphere. Even shadow bands were seen, both before and after totality, shimmering on the white-painted outside walls of the ship's cabin.
Venus and Mercury were still below our horizon, but the other three planets were very conspicuous. Fortunately the sun, at the start of summer, is surrounded in the sky by many bright stars, and we found that all of the first-magnitude stars were easy to find. Rigel and Betelgeuse, in Orion, happened to serve as excellent pointers to the sun, the three being almost equally spaced along a great circle. We even found second-magnitude stars, such as those in Orion's belt, when we knew just where to look for them.
After totality, I went to the radio room and sent a message to our colleagues on the Canberra, telling them of our success and wishing them the same luck when their turn came in another twenty minutes. Then, all hands assembled on the top deck for a success ceremony. To the accompaniment of the ship's band, a special eclipse flag depicting the eclipsed sun with corona, was hoisted to the highest mast to take a position just above the flags of the United States and Great Britain. This unusual banner had been flown only once before on the Olympia, the first ship chartered by our cruise organizers for their "Voyage Into Darkness" to successfully view the eclipse of July 10, 1972 from the North Atlantic. About the time our flag was raised, we received a message from the Canberra that they, too, had had a complete success. This time of jubilation was just right to go below for a champagne breakfast!
I had expected the return trip to San Juan would be a letdown, but it was nothing of the sort. Interest in, and enthusiasm for, the scientific and other cultural lectures were greater than ever. There were also parties, dancing, and the traditional passenger variety show the last night at sea, a show that included a brief recital by Captain Peter Jackson, who is a fine pianist as well as an excellent ship's master. We spent that last night, actually, in the harbor of St. Thomas. At midnight it became July the Fourth, and we were treated to a fine fireworks display from shore. By coincidence, the Olympia was anchored in the same harbor. Our eclipse flag was flying; we hoped that some of the crew members of the Olympia saw and remembered it.
As the reader must have discerned by now, there was much more to our eclipse cruise than having had the awesome experience of witnessing a spectacular celestial phenomenon. There are other memories, which we shall not soon forget: those horrible puns made by Wally Schirra at meal times: Arthur Clarke, who was seldom seen wearing shoes; Frances Wright, who was seldom seen at lunch because she was with her students doing a noon sight of the sun; Howel Williams, who found the roll of the sea a little much at times, and was seldom seen at any meal (indeed, his most brilliant lectures were delivered sitting down!); and Norm Macdonald, who before the eclipse was seldom asleep and after it was seldom awake. There were stimulating lectures, fascinating shore tours, top-notch entertainment, enjoyable socials and the drama and excitement of the rendezvous with the eclipse itself, with all the suspense of the weather, and the big question as to whether or not our technological ingenuity would be up to outmaneuvering the perversities of nature, so that she would allow us to share one of the most spectacular shows she can produce. Above all, perhaps, is the comradship of old and new friends sharing together a marvelous adventure, one that has already been relived in eclipse parties and reunions. There are other eclipses to come, and, doubtless, more "Voyages Into Darkness." Let us hope that they are all as fulfilling as this one was.
George O. Abell is professor of astronomy, and chairman of the department, at the University of California, Los Angeles. He received the Ph.D. degree in astronomy from the California Institute of Technology in 1957. Dr. Abell is well known for his combined abilities to do research as well as to teach and to popularize his science. This is evidenced by the fact that he was a lecturer at the Griffith Planetarium while working on his doctorate, and retained that position for four years after he got his degree. During the latter years he was also a guest investigator at the Hale Observatories where he studied clusters of galaxies, a subject that continues to be his main interest. He is the author of one of the most widely used college astronomy textbooks, first published in 1964 and revised five years later.
George Abell is a recent past president of our Society, and we are happy to present this breezy account of his recent encounter with the moon's shadow on the high seas, or: The Adventures of an Astronomer Afloat! The Editor
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