1608: Dutch spectacle maker Hans Lippershey files the first known patent application for a refracting telescope, although it is unclear whether he actually invented the device.
1609: Italian astronomer Galileo Galilei builds his own telescope and makes observations of the Moon, Jupiter’s moons, and other celestial objects, leading to the publication of his “Starry Messenger” in 1610.
1611: Johannes Kepler publishes “Dioptrice,” a treatise on optics that includes a description of a refracting telescope with an improved design.
1668: Sir Isaac Newton builds the first reflecting telescope, which uses a curved mirror instead of lenses to gather and focus light.
1675: Danish astronomer Ole Rømer measures the speed of light using observations of Jupiter’s moons with a telescope.
1781: Sir William Herschel discovers Uranus, the first planet to be discovered using a telescope.
1839: French physicist François Arago develops the first achromatic lenses for telescopes, which greatly improve image quality by reducing chromatic aberration.
1845: The first photograph of the Moon is taken using a telescope by French photographer Louis Daguerre.
1871: American astronomer Henry Draper takes the first photograph of a stellar spectrum using a telescope.
1963: The first radio telescope is built, allowing astronomers to observe and study radio waves emitted by celestial objects.
1990: The Hubble Space Telescope is launched, allowing astronomers to make unprecedented observations of the universe from space.
2021: The James Webb Space Telescope is launched, representing a major advancement in space-based astronomy with its ability to see further into the universe and observe the formation of the first galaxies.