Reflecting telescope
Mirror-based telescope scalable to large apertures.
Overview
Newton's reflecting telescope of 1668 replaced lenses with a mirror, eliminating chromatic aberration and enabling far larger apertures. Modern observatories are almost entirely reflectors, culminating in segmented mirrors tens of metres across.
Key discoveries
- Discovery of Uranus by William Herschel (1781)
- Resolution of spiral structure in nebulae (Lord Rosse, 1845)
- Hubble's Cepheid-based distance to the Andromeda nebula (1924)