A photographic refractor with aperture 0.33 m and focal length 3.438 m, giving a plate scale of 60″ to 1 mm. The usable field is about 2° × 2°. This type of telescope was designed in Paris by the brothers Paul Pierre Henry (1848–1905) and Prosper Matthieu Henry (1849–1903) in about 1880. Many such telescopes were constructed and were used for the Astrographic Catalogue and Carte du Ciel.