Astronomical observatories in Sweden
by Östen Bergstrand (1873 to 1948)

Even before Dunér's took over the leadership, the extensive meteorological observation activities in Uppsala had been transferred to a new institution, the meteorological observatory, and the magnetic observations had been taken over by the physical department. The Uppsala Astronomical Observatory was thus now able to devote its activities in part to purely astronomical research and teaching. With energy, Dunér tackled a reorganization of the business along the new lines. He managed to obtain funding for a new large double refractor by Repsold with a visual lens of 36 cm opening and a photographic one of 33 cm. The large tower was enlarged and fitted with a new swivel dome. Assistive devices were procured for the astrophotographic work. After Dunér's time, the instrument equipment has been further supplemented, partly with the help of individual donations, including two new astrophotographic refractors, so-called astrographs, equipped with Zeiss lenses of modern construction, and with measuring devices of various kinds for processing the photographic material.

At the same time, the entire observation facility has gradually been developed in accordance with the 'pavilion system': of the main instruments, only the large refractor is set up in the tower connected to the main building; all the others are located in independent observation pavilions with rotating domes.

Through these improvements and expansions, the Uppsala Observatory had developed into the foremost in the Nordic region in terms of the possibility of conducting modern astronomical research. A fairly extensive observational activity has also been conducted there in recent decades, mainly regarding determinations of stellar distances, studies of star groups and nebulae, photometric and spectral analytical studies and more. The characteristic of this entire research activity is that it was almost exclusively conducted using the photographic methods.

Of the many highly significant advantages that these methods bring in most cases over the older, only one may be emphasized here, which is extremely important precisely for our Swedish observatories. The climate in our country is not very favorable for astronomical observation activities. During certain parts of the year, the sky is mostly cloudy, sometimes for months on end. In addition, the summer months with their bright nights are useless for most types of astronomical observations. Since the surveys and measurements were to be carried out directly in the sky, in order to carry out a series of observations one often had to content oneself with working in rather poor conditions, which of course had a very detrimental effect on the nature of the results. Many kinds of observation work were simply impossible just because of the weather conditions. When applying the photographic procedure, one can concentrate the photographs in the sky on those occasions when it is fully clear and the air is particularly good, and thereby, so to speak, store a first-class observation material. A single photographic plate, whose exposure to the sky has taken a comparatively short time, can absorb thousands of stars and provide ample material for month-long measurement work, performed in peace and quiet without being disturbed by worries about the weather changes.