‘Excellentissimo tubo Dollondiana’: The Stockholm Observatory’s 10-foot Dollond achromatic refractor

Abstract

The instrument collection at the Royal Swedish Academy of Sciences houses a historically significant 10-foot achromatic refractor crafted by London instrument maker John Dollond. The telescope came into use at the Academy’s Observatory in Stockholm in 1761 and remained in service into the 1820s. This paper aims to add to the biography of this instrument, encompassing its six decades of active service and, after 150 years in storage, its transformation into an exhibition showpiece. The paper begins by introducing the telescope, its maker and the conflict involving Dollond and the Swedish mathematician and physicist Samuel Klingenstierna over the discovery of the achromatic lens. This dispute ultimately resulted in the telescope finding its way to the Stockholm Observatory. Subsequently, the paper delves into how Academy astronomer Pehr Wargentin perceived and utilized this state-of-the-art refractor, along with brief mentions of its use by his successors. The final section narrates how the telescope ended up in the permanent exhibition of the Stockholm Observatory Museum.