Großer Refraktor
The Großer Refraktor stands on Telegrafenberg in Potsdam, inside the Wissenschaftspark Albert Einstein. Its protective dome spans twenty-one metres across. Two tubes share one parallactic mount, forming a double refractor for photographic and visual observation.
Inaugurated in 1899 in the Kaiser’s presence, the instrument helped Johannes Hartmann discover the diffuse interstellar medium in 1904. Hartmann observed stationary calcium lines in spectroscopic binary stars. War damage in 1945 preceded modernisation in 1953, while operation ended in 1968. A Potsdam association formed in 1997 and led the restoration. Re-inauguration followed in 2006, leaving the protected monument fully operational.
The larger tube carries an eighty-centimetre objective and a 12.2-metre focal length for photography. The smaller lens measures fifty centimetres across. Its 12.5-metre focal length serves visual observation, while the roughly 250-tonne structure remains beneath the dome. Guided tours introduce visitors to the instrument and its restored structure. On clear nights, visitors can view stars through this historic instrument.
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