cost of 4465 Thalers and the plan was approved on 7 April 1800 and the required conversion was completed by June 1801. The construction work was supervised by Oberhofbaurat and Schlossbaumeister Bock. In 1797 Johann Georg Soldner arrived in Berlin as Bode's co-worker and in 1801 (″Astronomisches Jahrbuch für 1804″) Soldner's work appeared on the weight of light with implications for the curving of light rays in a gravitational field. In 1805 Jabbo Oltmanns came to Berlin and assisted Bode with his astronomical observations and his work on the Jahrbuch, in which also the first of his own articles appeared. Oltmanns also became an assistant to Alexander von Humboldt and processed the positional data from his just completed research expedition through Mid- and South America; during this work, Humboldt was ordered to Paris on a diplomatic mission after Napoleon's occupation of Berlin in 1806 and Oltmanns followed him in 1808. Until 1811, the astronomical institute financed itself almost exclusively from the monopoly on the calendar calculations, which had been conferred on the Academy at the time of its founding; in that year the Academy lost its calendar privileges and became dependent on the state budget and on charity. When the time came to seek a successor by virtue of Bode's retirement, both Carl Friedrich Gauß and Friedrich Wilhelm Bessel turned the post down. On the recommendation of Bessel, Johann Franz Encke, since 1822 Director of the Seeberg Observatory near Gotha, was called to Berlin by King Frederick William III in 1825 and named director of the Berlin Observatory. Thanks to the influence of Alexander von Humboldt, expensive instruments were obtained and with his aid Encke was also able to get the Prussian King to agree to the construction of a new observatory, situated on the edge of the city at that time. A condition was that the observatory should be made available to the public on two evenings in the week. The main instrument was a new refractor from the München (Munich) workshop of Joseph von Fraunhofer with an inner aperture of 9 inches (24.4 cm) and an inner focal length of 4.33 meters. Humboldt submitted a request for its purchase on 9 October 1828, including a meridian circle from the instrument maker of Berlin and a chronometer from the Berlin clockmaker. As a result, six days later, Frederick William III granted 8500 taler for the refractor, 3500 taler for