# Newtonian reflector

> A big concave mirror and a small flat at 45° — Newton’s reflector with an eyepiece off to the side.

![Newtonian reflector](https://www.loomrume.com/optics/stills/newtonian-reflector.png)

**Isaac Newton** · 1668 — shown to the Royal Society

A refracting spyglass of the 1660s threw coloured fringes — the same colour problem as the [prism](https://www.loomrume.com/examples/newton-prism.md) demo. Newton ground a metal mirror instead, put a small flat at 45° to send the focus out the side, and avoided glass dispersion altogether. The tube he showed in 1668 was a few inches long.

Speculum metal tarnished; later mirrors were silvered glass. The layout stayed. This bench is the classic: concave primary, diagonal, eyepiece, white sky in.

## Sources

- [Newtonian telescope](https://en.wikipedia.org/wiki/Newtonian_telescope)
- [Isaac Newton](https://en.wikipedia.org/wiki/Isaac_Newton)

## Links

- [HTML](https://www.loomrume.com/examples/newtonian-reflector)
- [Open in Studio](https://www.loomrume.com/experiments/new?template=newtonian-reflector)
- [llms.txt](https://www.loomrume.com/llms.txt)