Unfortunately the weather was unfavorable, but plates were exposed through light clouds, the longest exposure being 10 seconds. The photographs obtained show the prominences sharply defined, but only slight traces of corona are visible. Mr. Sutton, at Mautawali Kiki, and Drs. G. Fritsch, H. Vogel, and W. Zener, at Aden, were, from atmospheric and other causes, unsuccessful with refractors.
At the eclipse of August 7, 1869, many attempts were made to photograph the corona. In all cases where the image was enlarged before it fell on the plate, slight traces of the corona were obtained; while Professor Winlock and Mr. J. A. Whipple, at Shelbyville, with a 5½-inch lens of 7½ feet focal length, obtained seven pictures taken in the primary focus, one with 40 seconds’ exposure, showing more detail than had previously been photographed.
At this eclipse, Messrs. Hoover photographed the corona with a lens of 12 inches focus, and Professor Stephen Alexander also obtained photographs at Ottumwa some of which give good ideas of the coronal structure.
At the 1870 eclipse, December 22, a 4–inch Dallmeyer lens (rapid rectilinear), stopped down to three inches aperture, and with a focal length of thirty inches, was used by Mr. Brothers at Syracuse. Wet plates were used, and the photographs were taken through light clouds, the best of the pictures having had eight seconds’ exposure. Details in the corona are very well shown in these photographs. In discussing his results, Mr. Brothers says, “The photographs taken ... prove that the light of the corona is very actinic, and that several photographs of this beautiful phenomenon can be taken during the time of totality.” He further adds, “That it is impossible to obtain satisfactory photographs of the corona either with reflecting or refracting telescopes as ordinarily used is, I think, now conclusively proved.”
Professor Winlock, at Jerez, during the same eclipse, obtained two good photographs with ordinary telescopes; while Lord Lindsay, at Maria Louis Observatory, with a 12–inch mirror of 6 feet focus, obtained plates so much fogged as to be useless.
On December 21, 1871, splendid photographs were obtained at Baikul by Mr. Davis (Lord Lindsay’s observer), and by Colonel Tennant, J. B. Hennessey, Esq., and Captain Waterhouse, at Dodabetta. In each case Dallmeyer 4–inch rapid rectilinear lenses of thirty-three inches focus were used, the exposures varying from five to forty seconds. Herr Dietsch, in Java, also obtained two good photographs with a “lens of short focus,” with exposures of half and one-third second. Captain Hogg, at Jaffna, also got fair results with cameras 16 inches and 23 inches long. At the eclipse of April 6, 1875, Dr. Schuster, in Siam, obtained good photographs, although small, with an ordinary camera.
The eclipse of 1878 marked another departure in photography. Dr. Draper used wet plates, and got much detail in 165 seconds. Mr. Ranyard used Mawson & Swan’s extra sensitive dry plates, with a 13–inch lens of 6 feet 2 inches focus, and obtained photographs extending 6′ (one-fifth of a sun’s diameter) from the limb with exposures of one and three seconds. Professor Harkness, the director of the American operations, arranged two cameras, with 6–inch Dallmeyer lenses of 37.9–inch focus, and Mr. J. A. Rogers and Mr. Clark with these, using specially prepared dry plates made by Mr. Rogers, obtained two good series of photographs. In the report on the eclipse operations published from the United States Naval Observatory, Mr. J. A. Rogers not only discusses the value of photographs as compared with drawings, but enters fully into all the details of eclipse photography, concluding by strongly advocating the adoption of dry plates. Mr. O. L. Peers during this eclipse obtained a wet plate photograph showing greater extension of the corona than any of the dry plate ones, but there seems some doubt about the apparatus he used. He used either a 2⅛-inch or 3⅛-inch Voigtlander portrait lens, and exposed either for twelve or for twenty-three seconds. Mr. Peers says he used a 2⅛-inch lens, and twelve seconds’ exposure, while Voigtlander declares he makes only 3⅛-inch lenses of the focus 1:8 Mr. Peers used, and on examination of the photograph it is found that the trail of the moon on the plate indicates an exposure of twenty-three seconds. After the 1878 eclipse dry plates were universally adopted by eclipse observers.
The photographic arrangements of the expedition to Sohag, in Egypt, for the eclipse on May 17, 1882, were made by Captain Abney, the chief objects of the expedition being to photograph the spectra of the corona and prominences. Arrangements were also made by Captain Abney for corona photographs with a 4–inch lens of sixty inches focus belonging to him. The spectrum photographs taken show as many as thirty lines in the prominences, while the photographs of the corona obtained by Dr. Schuster with exposures of from three to thirty-two seconds show great extension of the corona with the most exquisite detail. These plates are also remarkable for the discovery of a comet in the photographs, although the comet was not seen by observers. Captain Abney and Mr. J. Norman Lockyer were responsible for the methods of photographic attack adopted by the English observers, Messrs. Lawrence and Woods, at the Caroline Islands, on May 6, 1883. The spectroscopic results and the corona photographs taken with the 4–inch lens of Captain Abney, previously used in 1882, were most successful. Janssen on this occasion used two objectives, one 6–inch and one 8–inch diameter, and using long exposures, photographed the corona extending two diameters from the sun, this being much further than it could be traced with a telescope.
Photography was again used on September 8, 1885, at the total eclipse in New Zealand.
At the eclipse of August, 1886, visible at Granada, Captain Darwin used a chronograph as devised by Dr. Huggins, consisting of a mirror inclined in a tube in such a manner as to enable photographs to be taken in the primary focus without the intervention of a flat. Good results were obtained. Dr. Schuster and Mr. Maunder used 4–inch lenses of 60–inch focus, and obtained good results. Their spectrum photographs were also successful. Professor Pickering, of Harvard, used a heliostat and a photo-heliograph of 38 feet focus, supported horizontally, but no results were obtained with this apparatus, although he was partially successful with his other instruments.