1710-1768

English astronomer who built some of the first telescopes to employ the design developed by French inventor Cassegrain. The Cassegrainian reflector used curved mirrors instead of lenses to concentrate light into a sharp and useable image for study. Although first designed in 1672, the technology to shape mirrors to the precise specifications needed for an effective instrument was lacking until 1740. The Cassegrainian reflector is still used today, as is its primary competitor, the Newtonian reflector.