The École Normale Superieure was given three 7.5 m diameter Würzburg Riese that the British had seized from the Germans during the war.

6 m wide railway tracks, one running east–west and one north–south were constructed, which would carry the equatorially mounted 40 t Würzburg antennas.

This design made possible a large collecting area and high resolution, with only moderate need for moving parts.

The mirrors were extended to their full, current size in 1964 and the telescope was officially opened in 1965 by Charles de Gaulle.

[4][1] The primary and secondary mirrors are formed by metal wire mesh with holes of 12.5 mm.

[4] The radio wave detector is cooled to 20 K to reduce noise from the receiver and thereby to improve sensitivity to the celestial radiation.

[3] Observational projects include:[4][3] The heliograph is a T-shaped interferometer made up of equatorially mounted antennas of several metres (mostly 5 m) diameter.

Half the cones are coiled in the opposite sense than the other, permitting the distinction between left and right circularly polarised radio waves.

Further, a phased array can be re-pointed at a different direction of observation instantaneously by changing the electronic signal delays between the individual antennas.

The temporal changes of signals from the Sun and Jupiter are very rapid, so that at Nançay very fast receivers have been developed for these observations.

[9] NenuFAR will be a triple instrument:[8] In recent years and decades, projects of astronomical observation have become international co-operations, due to the necessary pooling of expertise and funding.

[10] Located at Nançay and Westerbork, EMBRACE (Electronic Multibeam Radio Astronomy Concept) is a prototype installation for phase 2 of the SKA.

[7][10] ORFEES (Observation Radiospéctrale pour FEDOME et les Etudes des Eruptions Solaires) is a 5 m diameter antenna dedicated to space weather and prediction of solar flares.

It observes the solar corona daily between 130 MHz and 1 GHz and can monitor the radio emission of the Sun in near real time.

[7] An antenna, situated above the treetops on a 22 m high mast, has been monitoring the radioelectric quality of the Nançay site for 20 years.

[7] The large radio telescope, a number of display panels about the observatory, and one or two of the heliograph antennas can be seen from the car park of the visitor centre Pôle des Étoiles.

During opening times, the visitor centre offers a permanent exhibition about astronomy and the work of the observatory.