Instruments past and present
Early telescopes were supplied by the famed craftsman Giuseppe Campani. Cassini, an astronomer who worked in the early days of the Observatory, had used Campani's telescopes in the 1660s, and continued to do so when he moved to the Paris Observatory.
The Marly tower, moved to the observatory in 1685 for mounting telescopes, was demolished in 1705. The Marly tower was originally made for the Versailles water supply system (see Machine de Marly), but was moved to the southern gardens area near the Paris Observatory. The tower could hold the objective lens for extremely long focal length aerial telescopes.
In 1732 a quadrant instrument made by Langlois was established at the Observatory.
In 1804 a telescope of 8.4 cm aperture, made by Bellet, was established on the roof of the observatory. In 1807 a Short reflector telescope was acquired, and there were several instruments available including a 9 cm aperture Dollond telescope, and a telescope by Lerebours.
One of the special telescopes in the collection of the observatory, was the Passy telescope of King Louis XV. This telescope was built by Dom Noel in the late 18th century, and was a reflecting telescope with a 61 cm aperture bronze mirror. In 1805 the mirror was re-polished, but it was tarnished again within two years; it remained at the Observatory until it was dismantled in 1841.
A Lerebours telescope of 24.4 cm aperture was installed in 1823, at a cost of 14,500 francs. In 1835 Arago used this telescope to observe the return of Halley's Comet that year.
In 1837 the Gambey mural circle was installed, and also a transit instrument, also by Gambey.
In 1857 a refracting telescope of 38 centimetres (14.96 in) aperture objective, the Arago equatorial telescope, was completed. This telescope was proposed by director François Arago in 1846. It was installed in the east tower and was made by Lerebours. This instrument is known to have conducted photometry measurements of Jupiter's moons (there were only four known at that time) in the late 1880s.
In 1863 a large transit circle was installed, and in 1878 a meridian instrument. The transit circle of 1863 was made by Secretan and Eichens.
In 1875 a 120 cm aperture silver-on-glass reflecting telescope was built, for 400,000 francs.
This 120 cm diameter aperture telescope was a silvered glass mirror polished by Martin. However, when it was mounted it was realized the gravity altered its shape because of the mirror's weight, thus causing an image quality issue.
In 1886 a Henry astrograph with 13-inch objective was acquired.
For the 1907 Transit of Mercury, some of the telescopes used at the Paris Observatory included:
Foucault-Eichens reflector (40 cm (16 in) aperture)
Foucault-Eichens reflector (20 cm (7.9 in) aperture)
Martin-Eichens reflector (40 cm (16 in) aperture)
Several small refractors
The telescopes were mobile and were placed on the terrace for the observations.
