Musées de Langres – Maison des Lumières Denis Diderot – Musée d'Art et d'Histoire

This telescope is unsigned. Comparative analyses suggest that it was probably made by Claude Paris, a leading Parisian manufacturer of telescopes and microscopes from 1733 onward. The Gregorian reflecting telescope is composed of a main brass barrel and two optic devices. A primary concave steel mirror located at the bottom of the main barrel reflects the light – and therefore the image – back up to a smaller secondary concave mirror. This image can be observed at the other end of the telescope through an aperture at the centre of the primary mirror. The image is seen through the lenses of the eyepiece, which is the narrow barrel at the end of the main body of the telescope. A worm screw fitted along the length of the main barrel helps to adjust the distance between the two mirrors and focus the image. This telescope was used for both terrestrial and astronomical viewing because the image was not inverted.