American Eclipse Expedition to Japan: The Total Solar Eclipse of 1887

"Preliminary Report of Prof. David P. Todd, Astronomer in Charge of the Expedition."

Published by the Observatory

Amherst, Mass., 1888

I left Boston the 9th June for Japan, going by way of Montreal and the Canadian Pacific Railway to Vancouver, the coast terminus, and thence embarking for Yokohama in the steamship 'Abyssinia.'

Yokohama was reached the 8th July, and steps were at once taken toward locating the instruments in the most advantageous spot. I was most fortunate in having . . . permission to establish my station on the ruin of the celebrated old castle occupied by the Abe family until the revolution of 1868.

Our main instrument was a horizontal photoheliograph of nearly forty feet focal length. Two weeks' time was quite sufficient for the substantial completion of this instrument, in so far as the parts required for photographing the partial phases of the eclipse were concerned. Of these we had planned to secure 100 pictures; but I had determined also to attempt coronal photography with the same apparatus, hoping to obtain eight or ten negatives of the corona of such size that subsequent enlargement would be undesirable.

Special modifications of the exposing-shutters and the plate-holders had to be made, and a light-proof tube or camera the whole length of the telescope had to be constructed, before the complete drill for the eclipse could begin, and this required a week or ten days more. As was anticipated, too, we found on photographing artificial crescents--very slender ones--that no image of the plumb-line appeared on the plate: there was thus no initial line of reference for the measurement of the position angles. Mr. Hitchcock, whom I had appointed photographer of the Expedition, undertook a variety of experiments to overcome this difficulty, and with entire success.

To assist in the operations of the photographic house, we were fortunate in securing the services of Mr. K. Ogawa of Tokio [sic], a Japanese photographer of wide experience, and Dr. Y. May King of Amoy, also a highly skilled manipulator. For some minutes immediately before the beginning and after the end of totality, the partial phase exposures were to be made every 15 seconds; while the large plates for the corona, with exposures varying from 1 second to 15 seconds were to be handled as rapidly as possible. We found that there was a loss of about 5 seconds between the plates--or something like one-sixth the entire duration of totality. With so efficient a photographic corps, and the drill which we all underwent, I had the best of reasons for anticipating complete success.

I had long had the idea that, by means of a system of light rods, or of cords and pulleys, led from the heliostat into the photographic house, the chief astronomer making the exposures might have the reflecting mirror under his immediate and constant control, and thus dispense with the customary assistant at the heliostat pier for adjusting the mirror in right ascension and declination. All the devices for this rather complex system were practically executed by Mr. Pemberton, and sufficed to give me perfect command of the mirror from the dark room.

I had an occulting-disk mounted on a rod attached firmly to the gable of the photographic house, so that its shadow as cast by the eclipsed sun would fall about fifty feet away, in the area enclosed by the upper castle wall. Here I stationed Mrs. Todd, assisted by Professor Kikuchi, of the Imperial University, and provided with all the paraphernalia for seeing and sketching in their correct relations the faint, outlying streamers of the corona. On the north-west corner of the castle I stationed Mr. K. Acino, a student of astronomy in the University, and interpreter to the expedition . . . he was to make detailed and precise observations of the diffraction bands, and to observe, if possible the sweep of the lunar shadow across the extensive rice-fields below.

The forenoon gave us a perfect sky, with no indication whatever of approaching cloud: all were confident of entire success. But about an hour before the time of first contact, a slender finger of cloud began to rise from the west, coming at first directly above the summit of Nasu-take, a volcano about 25 miles away, and which had sprung into unwonted activity during the past night, belching forth for hours enormous volumes of smoke and steam. The dense clouds . . . lay over the sun until the eclipse was past . . . . In general, the whole of the main island was obscured on the eventful afternoon.