Nançay Radio Observatory, Radio astronomy observatory in Nançay, France

The Nançay Radio Observatory is a facility in the Cher department, about 30 km from Bourges, with instruments operating since 1956. Its main telescope, completed in 1965, uses a flat 200 m by 40 m metal-mesh mirror that tilts to reflect radio waves onto a fixed spherical mirror 460 m south. The site also hosts a T-shaped radioheliograph, a decametric array, and the NenuFAR and LOFAR networks.

Radio astronomy began in France when Yves Rocard's team at the École Normale Supérieure used three 7.5 m Würzburg-Riese radar dishes seized by the British. A 150-hectare plot near Nançay was bought on 25 November 1953, and the station opened on 21 October 1956. The Grand Radiotélescope, built from 1960, was inaugurated by Charles de Gaulle on 15 May 1965; observations started in 1967.

The visitor center presents astronomy exhibitions and operates a planetarium where groups can learn about the research conducted here. This space helps people understand how radio telescopes work and why they matter for studying the universe.

The site sits in a quiet woodland area and is accessible to visitors who want to spend time exploring the exhibitions and planetarium. It's worth checking in advance if tours or special events are scheduled, since the facility is located in a remote setting.

The heliograph's 19 east-west antennas sit on a 3.2 km baseline and its 25 north-south antennas on a 2.5 km one, forming a T. It observes the Sun seven hours a day between 150 and 450 MHz, matching the resolution of the naked eye in visible light.