The Reichenbach & Ertel Meridian Circle at the Tartu Old Observatory: Great Moments from the History of a 200 Years Old Instrument

Abstract

This article examines major events in the 200-year history of the meridian circle of Tartu’s (Dorpat) Old Observatory based on archival sources and primary literature. It analyses why and how the Reichenbach & Ertel meridian circle was ordered in 1817/1822 and gives an overview about the three major works done with the help of it: the position measurements of 3220 stars in Friedrich Wilhelm Struve’s famous catalogue of binary stars (1827), the Struve Geodetic Arc (UNESCO Heritage site since 2005), and the so-called zone observations in the last quarter of the 19th century under the leadership of Ludwig Schwarz, when the meridian circle and the observatory were already somewhat deteriorated. Besides contributing to large projects, the Tartu meridian circle was used for everyday astronomical timekeeping and training of the younger generation of astronomers for at least 140 years (1822-1964).