IX. Drawings of the coroma from photographs at total eclipses from 1896 to 1922

In the various Eclipse Expeditions from the Royal Observatory or sent out by the Joint Permanent Eclipse Committee, a number of excellent photographs of the Corona have been taken. Drawings of these photographs, embodying the more important features, have been made, but no reproductions have as yet been published. As the form of the Corona is intimately related to other Solar phenomena, it is desirable that permanent records should be kept of its appearance at every Eclipse. Sir William Christie took a great interest in obtaining large-scale photographs of the Corona. By the use of a negative enlarging lens he avoided the necessity of telescopes of very great focal length. Even so, the total length of the instrument was 12 feet. The equatorial mounting of such a telescope in Eclipse Expeditions presents some difficulty, as it necessitates the transport and erection of heavy mountings for the instrument and provision for its housing accommodation. These were largely obviated by the use of the cælostat introduced in 1896 by Prof. Turner and constructed for the Expeditions by Dr. Common.