Newtonian reflecting telescope
Telescopio reflector newtoniano
- Date
- 1668 · confidence high
- Place
- Cambridge, England
- Credited to
- Isaac Newton; earlier proposals by Gregory (1663) and Cassegrain (1672)
- People
- 👤 Isaac Newton1642–1727👤 James Gregory1638–1675
- Field
- Communication
⚠️ Disputed: the sources disagree.
What it is
A telescope using a concave metal mirror (speculum) instead of an objective lens, with a flat secondary mirror at 45°, avoiding chromatic aberration. Newton presented it to the Royal Society in 1672.
James Gregory designed a reflector in 1663 that he could not build; Cassegrain proposed another in 1672. Newton was the first to build a working one.
What it led to
- Large mirror telescopes (Herschel, Rosse) and galactic astronomy
- Speculum alloys and mirror polishing
- Newton's theory of colours and light
Built on
- Conic sectionsc. 200 BCE
- On Burning Mirrors: focus of the parabolic mirror (Diocles)c. 200 BCE
- Glass mirror with metal backingc. 100 CE
- Refracting telescope1608
- Dispersion of white light and theory of colour1666
- Concave mirrors
- Newton's optics (decomposition of light, 1666)
Made possible
- Cassegrain mirror system1672
- Silvered-glass mirror and the Foucault test1857-1858
- Maksutov telescope1941
- Dobsonian telescope1965
- Hubble Space Telescope1990
- Herschel's telescope (1789)
- Cassegrain telescope
- Silvered glass mirror (19th century)