History of the Telescope

Glass discovery

3500 BCE

Phonenicians cooking on sand discover glass.

Lenses

1400

Lenses were discovered

Hans Lippershey

1608

In the Netherlands, Hans Lippershey discovers that holding two lenses up some distance apart bring objects closer. He applies for a patent on his invention. This is the first documented creation of a telescope. The idea is independently developed by Jacub Metius and Sacharias Janssen. The patent to Lippershey is denied.

Thomas Harriot

1609

Thomas Harriot (1560 – 1621) English astronomer, mathematician, ethnographer, and translator becomes the first person to make a drawing of the Moon through a telescope, on July 26, 1609, over four months before Galileo.

Galileo

1609

Galileo, after simply hearing that the device was invented, builds several telescopes of his own and turns them toward the heavens. He dared to publish his findings and was nearly burned at the stake for it. There are other earlier recorded astronomical uses including viewing stars with Lippershey's own first telescope during its demonstration and Thomas Harriot's views of the moon not long after.

Marin Mersenne

1636

Marin Mersenne hit upon the idea of using two paraboloidal mirrors instead of lenses, but he never builds this telescope, having been persuaded by Descartes that it could never work. The main advantage of using mirrors over refracting lenses is that mirrors focus all points of the spectrum at the same point--no chromatic aberration!

Rene Descartes

1637

Rene Descartes demonstrated that speherical lenses cannot produce pinpoints of light. Although the lenses corrected for spherical abberation, they introduced another probelm--chromatic abberation, which made the problem worse. Chromatic abberation means that different colors are focused at widely differing points, producing smeared images with halos around them.

Newton

1668

Newton produces the first successful reflecting telescope, using a two-inch diameter concave spherical mirror, a flat, angled secondary mirror, and a convex eyepiece lens.

Johannus Hevelius

1673

Johannus Hevelius realized that the longer the telescope was, the closer together the different colored points of light would be at the focal point, yielding a sharper image. He constructs a telescope 140 feet long which probably gave very sharp images, but it was almost impossible to keep the two lenses aligned because the supporting structure (usually a long tube) could not be made rigid enough.

Christian Huygens

1675

Christian Huygens suggests getting rid of the supporting structure and mounting the objective lens on the top of a long pole. These were called "aerial telescopes" because they were open to the air. They were also much easier to build and use. At the same time, Huygens developed a compound negative eyepiece using two air-spaced convex lenses. This arrangement cancelled out some of the chromatic aberration that occurred in a single lens eyepiece.

James Short

1730

The Scottish Instrument maker James Short invents the first parabolic and elliptic, distortionless mirror ideal for reflecting telescopes.

H. Dennis Taylor

1893

H. Dennis Taylor, optical manager of T. Cooke & Sons of York, makers of astronomical telescopes, designed and patented the revolutionary, and now famous, triplet design (British patent no. 1991). This lens eliminated the optical distortion at the outer edge of lenses. The Cooke Triplet was a significant improvement of the Dolland triplet of more than a century earlier.