Have you ever read H.G. Wells’ War of the World? It was first serialized in 1897, and the main character goes to an astronomical observatory to see explosions on the surface of the planet Mars at the beginning. This made me feel like I really don’t know anything about the history of astronomy (I already know I didn’t know a lot about astronomy already, except for that Pluto story). I asked myself:
Who Invented the Telescope?
Before exploring the history of the invention of the telescope, what is a telescope? Let’s take a look at Merriam-Webster’s definition:
A usually tubular optical instrument for viewing distant objects by means of the refraction of light rays through a lens or the reflection of light rays by a concave mirror
Apparently, it’s one of those inventions for which multiple people claim to have invented it. Officially, we can trace the invention of the telescope to Hans Lippershey, an eyeglass maker in the Netherlands, who submitted a patent in 1608.
A Dutchman named Jacob Metius, an instrument maker, also applied for a patent for the telescope a few weeks after Hans Lippershey did. The Dutch government went with Lippershey anyway. Apparently, there are claims that he stole it from another eyeglass maker named Zacharias Jansen. They were colleagues living in the same city (Middleburg). But everything is not clear on that front, some facts didn’t corroborate every claim made.
Another angle is the British one. Elements found in Thomas Digges’ 1571 book “Pantometria” referred to a “fare seeing glass”—which would be based on an idea by medieval English philosopher Roger Bacon. That said, it was probably a “perspective glass,” not a telescope. There are not enough details to be certain.
Also, let’s not forget the notebooks of Leonardo da Vinci and Girolamo Fracastoro that contain imprecise information about water-filled crystals or a combination of lenses to magnify the Moon. Or the later claims about the French Juan Roget.
In the end, it’s Hans Lippershey who got the patent that led to other experiments by scientists from other countries.
The Evolution of the Telescope
After hearing about the “Dutch perspective glasses” in 1609, Italian astronomer, physicist, and engineer Galileo Galilei designed his own telescope—with about 3x magnification. He quickly improved on it, going up to 9x magnification (and later up to 20x), and introduced his creation to the Venetian Senate. He started to sell them to merchants but also worked on his own telescopic astronomical observations.
In the first months of 1610, Galileo Galilei discovered four satellites orbiting Jupiter. He then asked for German astronomer, mathematician, and astrologer Johannes Kepler’s opinion about it. This led Kepler to publish his own telescopic observations of the moons, and also to investigate the telescopic lenses. This led to an improved telescope—call the Keplerian telescope, using a convex lens as the eyepiece instead of Galileo’s concave one. This allowed for a much wider field of view and greater eye relief, but the image for the viewer is inverted. This design also allowed for higher magnifications and for use of a micrometer at the focal plane in order to determine the angular size and/or distance between objects observed.
The design of the Keplerian telescope was later improved by Dutch mathematician, physicist, astronomer and inventor Christiaan Huygens. First, in 1655, he discovered the first of Saturn’s moons, Titan, using a refracting telescope. In 1662, developed “the Huygenian eyepiece,” a telescope with two lenses in order to diminish the amount of dispersion.
And then, in 1668, Isaac Newton introduced the first reflector, a small flat diagonal mirror to reflect the light to an eyepiece mounted on the side of the telescope. The second one came in 1672, designed by Catholic priest Laurent Cassegrain.
The next improvement took time. In 1721, English mathematician John Hadley developed ways to make precision aspheric and parabolic objective mirrors for reflecting telescopes. In 1733, British lawyer and inventor Chester Moore Hall built a telescope that used an achromatic lens that reduced color aberrations in objective lenses and allowed for shorter and more functional telescopes. His invention was not well-known at the time—this only changed in 1758 in fact.
Through the years, new discoveries led to new improvements. It never stops. For more information, go check “The History of the Telescope” written by Henry C. King.