The Estonian-German optical engineer Bernhard Voldemar Schmidt (1879-1935) in his workshop. Despite having lost his right arm in an accident with explosives, Schmidt ground and polished mirrors for telescopes unaided. He is well known for the design of a new telescope named after him. The Schmidt telescope is formed by a primary spherical mirror with a glass corrector plate of complicate figure placed in front of the primary mirror at its centre of curvature. In this way he created a telescope almost free from optical aberrations such as coma and spherical aberration. The Schmidt telescope is usually used as a camera, and it revolutionised optical astronomy.