Object of the month: The first auroral cameras were developed in Alta
The object of the month for November is a "Krogness-Størmer camera", the first camera produced especially for taking photographs of the northern lights. It was developed 1909-1915 and used in extensive research projects in Alta. A considerable number of "Norwegian auroral cameras" were sold abroad. They used all over the world at locations where the northern lights were studied between 1910 and 1950.
Ole Andreas Krogness, the first director of the Haldde Observatory in Alta (1912-1918) cooperated with professor Carl Størmer in making the camera. Krogness made the final version of the camera at the Haldde Observatory. While Krogness had his headquarters on the mountain peak, Størmer stayed at a hotel in Bossekop in the centre of Alta. Størmer did extensive photographic work from a network of research stations down by the Alta Fjord in 1910 and 1913. Between 1910 and 1940 Størmer and his staff took more than 100 000 photos with this type of camera.
The importance of auroral photography
In 1885 attempts were done to take a picture of the northern lights using a camera with an exposure time of 8 minutes. The first published photograph of the northern lights was taken in Alta by the German astronomer Martin Brendel in 1892 with an exposure time of 7 seconds. In 1915 six photographs could be taken in rapid succession using the Krogness-Størmer camera on one photographic plate with an exposure time of 1 second.
It was absolutely necessary to use a camera when documenting the northern lights in order to get a purely objective concept of the aurora. Before the invention of photography scientists attempted to document the fleeting aurora by drawing the displays. Photographs were also needed to prove how high the northern lights were above the Earth.
Measuring the altitude
As early as 1838-1839 the so-called Recherche-scientists had determined that the altitude of the northern lights was between 90 and 150 km above the Earth. By taking pictures at the same time from different places along the Alta Fjord Størmer managed to prove that this calculation was correct. The maximum intensity of most of the aurora borealis was at a height of about 100 km and there is practically not any northern lights at altitudes under 85 km.
In memory of Kristian Birkeland
The development of the auroral camera is described in a thesis Krogness wrote in 1920 with another important Norwegian physicist, Lars Vegard. The title of the publication is «The Position in Space of the Aurora Polaris from Observations made at the Haldde-Observatory 1913-1914». The dedication is "In Memory of our Teacher Kr. Birkeland." Kristian Birkeland was born 150 years ago in 1867, and he died in Tokyo in 1917.
Hans Christian Søborg