What kind of machine did Leonardo da Vinci design for grinding concave mirrors?

Leonardo da Vinci designed a mirror-grinding machine for shaping concave mirrors.

Leonardo studied optics, reflection, and the geometry of curved surfaces throughout his notebooks. His designs sought to mechanize the difficult process of grinding and polishing a concave mirror, which required a carefully controlled matching motion between the tool and the mirror blank.

A concave mirror can collect and focus reflected light, so accurate curvature is essential. Leonardo’s proposed apparatus used mechanical motion to make the grinding process more regular than purely hand-guided work.

The design belongs to Leonardo’s broader investigations into optical instruments and light. It should not be confused with a telescope: the machine was a manufacturing device for producing a mirror, not an observing instrument itself.