First floor

Octant: invented in 1731 by John Hadley, it takes its name from its ivory arc, which corresponds to the eighth part of a circle (45°). The frame was mainly constructed from ebony wood, while the arc and the engraved plaque bearing the names of the maker and the owner were made of ivory. Each instrument came with its own case.

Sextant: an evolution of the octant, it is an instrument used to measure the elevation angle of a celestial body above the horizon. It is so named because its arc is the sixth part of a circle (60°). Compared to the octant, it was more practical, as it was made of brass and silver instead of wood, as well as being more compact, manageable, and durable.

Refecting circle: created around the mid-18th century by the German astronomer Johann Tobias Mayer (1723–1762) to refine the measurement of angles, it features a full 360° circle. It was used to determine latitude during night navigation. In 1787, Jean-Charles de Borda perfected its design, giving his own name to the model.

Tellurium: a 19th-century educational instrument used to explain the movements of the Moon around the Earth and both around the Sun (the latter represented by a candle, whose light projected onto the Earth indicated the position of the Sun throughout the year on a dedicated calendar).