Studies of Aurora ¹

Abstract

ONE or two photographs of aurora seem to have been taken before, but Prof. Störmer is the first to meet with marked success. In the earlier of the volumes before us he describes with full detail the apparatus and methods employed in photographing aurora during a stay of some months at Bossekop, in the extreme north of Norway, early in 1910. Photographs were taken by Störmer and an assistant from the two ends of a base of about 41/4 kilometres, simultaneity of exposure being: secured by telephonic signal. Using special plates, satisfactory photographs were obtained with a few seconds' exposure. One or more prominent stars were always included in the photograph, and the time was carefully noted. From the known co-ordinates of the stars, it was thus possible to fix the position of the auroja. The base was long enough in general to give a parallax which could be measured with sufficient accuracy to determine the approximate position and height of selected prominent points. The heights calculated for the different auroras varied from 36 to 461 kilometres. Fig. 1 shows a photograph—from the original negative—taken with 3 seconds' exposure; Fig. 2 is an enlargement, the original of which had a 5 seconds' exposure.