National Geographic : 1970 Aug
National Geographic, August 1970 eclipse of May 30, 1965, hitting only remote islands. On July 10, 1972, the shadow will cut through inhospitable areas of Russia, Alaska, and Canada, before leaving land at Nova Scotia. The following major eclipse, on June 30, 1973, will occur over the Sahara. Washington, Oregon, Idaho, and Montana will lie within the umbral shadow on Febru ary 26, 1979. The U. S. East Coast must wait until August 21, 2017,for its next total eclipse. Fortunately for professional and amateur astronomers, the eclipse of March 7, 1970, represented a welcome exception to the rule of inaccessibility. The last total solar eclipse to occur over the eastern United States in this century cast its shadow across the homes of more than a million and a half people from Mexico to Newfoundland. Shadow Grazes Edge of North America Starting over the Pacific, the umbra first touched land in southern Mexico (diagram, page 232). The wave of midday darkness crossed the Isthmus of Tehuantepec and traversed the Gulf of Mexico before striking land again in northern Florida. The shadow streaked up the coast of Georgia, South and North Carolina, and Virginia, then quickly swept across Atlantic waters to blanket Nan tucket Island and touch Nova Scotia. The three-hour journey ended at sea beyond New foundland, 8,500 miles from touchdown point. Undoubtedly more people traveled to see this eclipse than any other in history. Some fifty million people lived within a day's drive of the umbra's path, from 80 to 100 miles wide. Countless thousands lined highways and beaches during the eclipse, awaiting the two to three minutes of totality to watch a vision of rare beauty, the sun's corona. Totally or partially, the eclipse could be seen over nearly every section of North America. Many interested scientists, however, estab lished observation posts not in the populated centers of the East but in the mountains and valleys of southern Mexico. There we were promised the clearest weather and longest duration of totality, about 31/2 minutes. Our 17-member expedition, sponsored by the Harvard College Observatory, the Smith sonian Astrophysical Observatory, and the National Geographic Society, chose as its base of operations the Indian community of Miahuatln.* Some 300 miles southwest of Mexico City, the town lies in the midst of magnificent archeological remains from the Zapotec civilization. The state government at Oaxaca, 50 miles north of Miahuatlan, arranged for a suitable observation site and headquarters. Our advance party arrived in Mexico on February 7, allowing only a month to set up our complex equipment. The temporary quar ters delighted us. We had two rooms and the courtyard of an old music school, the Escuela Filarmonica Municipal, atop the tallest hill in town. The school's high adobe walls blocked the sweeping winds and dust, and offered protection from friendly but curious Miahua tlecans who might have unwittingly inter fered with our work. Electric lines, toilets, and running water *Additional support came from the Air Force Cam bridge Research Laboratories; National Science Founda tion; Austin Stanton Foundation; Duncan H. Read of Middleburg, Virginia; John J. Terlep of Pueblo, Colorado; and Videonics, Inc., of Cambridge, Massachusetts. Awesome rendezvous of sun and moon draws villagers to Miahuatlan's main square and cathedral roof. Some watch the progress of the eclipse through smoked glass or goggles of dense film. Eclipse day nearly doubled the population of this Indian town of 16,500; the area offered astronomers from more than a dozen nations clear skies and a long period of totality-3 minutes, 23 seconds. Awaiting darkness at noon (left), Doctors Menzel, right, and Pasachoff check the solar image on the spectrograph that separates it into component colors for analysis. A ghost image of the partial eclipse, reflected in the camera lens, appears beside them.