No coin nor oath required. For personal study only.
About two years ago a 9-inch astrographic camera lens was designed by I. C. Gardner, chief of the optical instruments section, and last year this lens was constructed in the Bureau's optical shop from glass produced by the Bureau's glass plant. The lens, which is of the telephoto type, consists of 4 components grouped into two well separated doublets, and was specially constructed for eclipse work. It was corrected for a field 20 inches square, corresponding approximately to 4ยฝ degrees.
A camera and mount for this lens was constructed of aluminum. In designing the mount the purpose was to make the complete equipment as light as possible for ease of transportation and to make the camera self-contained so that the focusing could be done in the laboratory before the equipment was packed for shipment. The plate holder was driven by clockwork so as to follow the sun's image, the camera remaining stationary.
The National Geographic Society and the Bureau cooperated in sending Doctor and Mrs. Gardner with this apparatus to Ak Bulak, in western Siberia, where photographs were made during the total eclipse of June ~9, 1936. Six satisfactory color films and two black and white negatives of the corona were made. On account of the excellent definition over the entire field, the outer corona can be traced to the extreme edges of the plates. The structure of the inner corona, particularly those lines indicating the presence of magnetic fields, is also faithfully recorded.
At the request and with the financial support of the Bureau of Aeronautics, Navy Department, an investigation * Communicated by the Director.
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