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3500 BCE
Phonecians discover how to make glass
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A man discovers that putting two pieces of glass some distance apart makes objects appear closer
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 makes the first drawing of the moon
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 build his own telescopes
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. -
Johannes Kepler changes the lens used
Johannes Kepler switches from a concave eyepiece to a convex eyepiece. This not only allowed a larger field of view, but it allowed for the projection of images (such as the sun) onto a flat white screen. Although the images are inverted, Kepler demonstrates how a third convex lens turns the images right-side-up again. The use of a third lens also degrades the images, so this form of the telescope is not widely used. Most used for military purposes. -
Rene Descartes discovers that spherical lenses cause a phenomena
After Kepler said the human eye is hyperboloidal, Rene Descartes demonstrated that spherical lenses cannot produce pinpoints of light. After studying both lenses he demonstrates that different combinations of hyperboloidal lenses or elliptical lenses will produce a pinpoint of light and a sharper image. His lenses fail.They introduced another problem- a chromatic aberration.This means that different colours are focused at widely differing points, producing smeared images -
James Gregory designed a new telescope
James Gregory designed a telescope using a concave primary mirror (slightly hyperboloid) concave ellipsoidal secondary mirror. The first mirror gathers the light and reflects it onto the secondary. The secondary mirror focuses the light back through a hole in the primary mirror. This is the basis for many telescopes made today, but the opticians of his time were not able to produce mirrors of high enough quality to give good results. -
Newton produces a telescope
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. As is often the case in physics, the simplest solution is often the most practical one. The reflector telescope that Newton designed opened the door to magnifying objects millions of times--far beyond what could ever be obtained with a lens. -
Robert Hooke demonstrates how to shorten the tube
Robert Hooke demonstrates how to shorten the tube by using three or four perfectly flat mirrors to reflect the image back and forth in a shorter tube. A 60-foot long telescope can be reduced to 12 feet long, greatly simplifying support and stability. -
Cassegrain developed a similar design
Cassegrain proposed a similar design using a convex secondary mirror that allowed the tube to be shortened even more. More importantly, it cancelled abberations from the primary mirror and would have resulted in much sharper images, had opticians been able to produce quality mirrors. It is interesting that Gregory, Cassegrain, and later Newton were able to invent designs that were so far ahead of their time that no one could actually make one. -
Johannus Hevelius
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. -
Aerial telescopes were invented
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. -
Scottish instrument maker invents a different telescope
James Short invents the first parabolic and elliptic, distortionless mirror ideal for reflecting telescopes. Short accomplished this in a very practical manner: Since parallel rays nearer the center of a spherical mirror overshoot the marginal rays coming from the edge of the mirror, why not just deepen the center to bring all the rays of light to the same point of focus? James Short built over 1,360 telescopes. All had speculum mirrors. His instruments were on the ship with Captain Cook -
John Dolland improves a different lens
John Dolland improves upon the achromatic objective lens by placing a concave flint glass lens between two convex crown glass lenses. This triplet uses the natural differences between the refractive indices of the two types of glass to cancel out chromatic aberration even more. Some historians claim that the triplet was introduced in 1765 by Peter, son of John Dollond. Many excellent telescopes of this kind were made by him. -
A british man patents a telescope
Dennis Taylor, optical manager of T. Cooke & Sons of York, designed and patented the revolutionary, triplet design.This lens eliminated optical distortion at the outer edge of lenses. The Cooke Triplet was a big change over the Bolland triplet of more than a century earlier. The cooke triplet, is made of three different types of glass. It has baryta light flint glass. It has boro-silicate flint glass, and has Schott's light silicate crown glass. The lenses are not touching