15-inch Double Refractor Astrograph

In the westernmost part of the observatory grounds, the dome of the historic astrograph rises on a small hill. This double telescope installed in 1911 - one for photography and a second for visual observation and tracking - enabled participation in the international photographic sky survey Carte du Ciel. The positions, proper motions and brightnesses of stars were measured and a large number of variable stars, comets and minor planets were discovered. The Carl Zeiss blink comparator, financed by Albert Freiherr von Rothschild, was used to evaluate the celestial images.


To the west of the main building is the Coudé Tower donated by Albert Freiherr von Rothschild. The main instrument, which gives the building its name and is very rare worldwide, was of the Coudé type and its complicated beam path with plane mirrors behind the 38cm objective enabled a fixed and thus stable installation of heavy analytical instruments, especially the spectrograph still used in teaching. On the dedication plaque above the entrance to the building, the letters referring to the donor Rothschild in the Third Reich have been made illegible, but they are still visible in special light.