Following the successful restoration, the association continues to support the interests of the Great Refractor. It contributes its specialist expertise, keeps the public’s interest alive, organises guided tours and observation evenings for visitors, and continues to seek donations, which are essential for the preservation of the Great Refractor.
Foundation and scientific purposes
One of the most renowned scientific achievements of the Astrophysical Observatory Potsdam was the introduction, encouraged by the first Director, H.C. Vogel, of the photographic plate for the determination of radial velocities of stars. Observations in those days were carried out with a 30-cm refractor, which rather limited the application to bright stars; in order to include fainter stars in this prestigious programme, more powerful telescopes were required.
The idea to construct what in those days was considered to be a huge astronomical telescope had already been discussed shortly after the founding of the Observatory in 1874. In 1889 a double refractor, with apertures of 32.5 and 23.5 cm and a focal length of 3.4 m, had just been mounted in the Photokuppel to the west of the main Observatory building; it was used mainly for cartography of northern-hemisphere stars as part of the Observatory’s contribution towards the Carte du Ciel which had been planned by the Paris congress of astronomers in 1887. Although this instrument was very practical and successful for taking photographic records of star fields, it was to small to take over the spectroscopic observation of radial velocities.
Plans for a new and bigger double refractor had been proposed by Vogel in 1890. The preference for a refractor rather than a reflector was due to the relatively primitive technology of the latter at the time, whereas the necessary technical experiments with big lenses could be carried out in the Observatory’s own laboratories. The dimensions of the lenses were carefully calculated according to the laboratory tests of the properties of different kinds of glass.
The large telescope, called the Great Refractor was completed just before the turn of the century, and was inaugurated in the presence of Emperor Wilhelm II on August 26, 1899.
You can save the future of the instrument by a donation to
Förderverein Großer Refraktor Potsdam e.V.
account number: 350 201 1809
MBS Potsdam BLZ 16050000
IBAN: DE28 1605 0000 3502 0118 09
BIC: WELADED1PMB
Text: Dr. G. Scholz; Arrangement: Kurt Arlt