Leiden Observatory () is an astronomical institute of Leiden University, in the Netherlands. Established in 1633 to house the quadrant of Rudolph Snellius, it is the oldest operating university observatory in the world, with the only older still existing observatory being the Vatican Observatory. The observatory was initially located on the university building in the centre of Leiden before a new observatory building and dome were constructed in the university's botanical garden in 1860. It remained there until 1974 when the department moved to the science campus north-west of the city. Notable astronomers that have worked or directed the observatory include Willem de Sitter, Ejnar Hertzsprung and Jan Oort. History 1633–1860 Leiden University established the observatory in 1633; astronomy had been on the curriculum for a long time, and due to possession of a large quadrant built by Rudolph Snellius, Jacobus Golius requested an observatory in which to use it. The observatory was one of the first purpose-built observatories in Europe. Though Golius used the observatory regularly, no publications came from its use by him. It is not known whether Golius had any instrumentation other than Snellius' quadrant at the observatory. In 1682 Burchardus de Volder became professor of mathematics at the university and thus took over responsibility for the observatory. During his tenure, the observatory was enlarged, including a second turret to house a brass sextant which he purchased, and the rebuilding of the old turret. Both turrets had rotating roofs. Upon retiring in 1705, de Volder handed over a catalogue of instruments which showed that the observatory owned two other quadrants, a 12-inch telescope, two objectives, and several smaller telescopes. For the next two years, Lotharius Zumbach de Coesfeld ran the observatory until his appointment as professor of mathematics in Kassel in 1708. Between then and 1717 the observatory went without a director until Willem 's Gravesande was appointed director. During his time at the observatory, 's Gravesande purchased a number of new instruments including new telescopes and tools, before his death in 1742. 's Gravesande's successor was Johan Lulofs who used the observatory to observe Halley's comet in 1759 and solar transits of Mercury (in 1743 and 1753) and Venus (in 1761). In November 1768 when Lulofs died, Dionysius van de Wijnpersse took over responsibility for the observatory until Pieter Nieuwland became its director in 1793 for a year until he died in 1794. For a number