Artifacts that could be lenses found in a sacred cave on Mount Ida, Crete date to this period.

Chinese philosopher Mozi writes on the use of concave mirrors to focus the sun's rays.

Aristophanes writes about the use of a burning glass in his play The Clouds, first performed in this year.

This is the legend of the burning of the Roman fleet at Syracuse through the use of specially directed mirrors arranged by Archimedes. Modern experiments indicate it was a realistic possibility. During the fifteenth and sixteenth centuries solving the puzzle of how it was done became popular with scientists. Cavalieri and others correctly determined that the science behind the burning mirror was in many cases the same as the science behind the reflecting telescope.

Seneca the Younger describes magnification by a globe filled with water: 'Letters, however small and indistinct, are seen enlarged and more clearly through a globe of glass filled with water.'

Pliny the Elder 'And yet, we find that globular glass vessels, filled with water, when brought in contact with the rays of the sun, become heated to such a degree as to cause articles of clothing to ignite.' I find it stated by medical men that the very best cautery for the human body is a ball of crystal acted upon by the rays of the sun.

Visby lenses possibly used to make a telescope. The lenses may have been imported from the Middle-East via Viking trading routes, but there is also evidence of local manufacture of lenses.

Ibn Sahl completes a treatise On Burning Mirrors and Lenses, describing plano-convex and biconvex lenses, and parabolic and ellipsoidal mirrors.

Ibn al-Haitham (Alhazen), a Muslim academic from what is now Iraq, writes treatise Kitab al-Manazir - 'Book of Optics'. Discusses the optics of lenses and mirrors and some say he even discovered the law of refraction (Snell's Law). Also discussed camera obscura as had the Greeks before him.

Robert Grosseteste, an English bishop, describes the use of 'optics' to '...make small things placed at a distance appear any size we want, so that it may be possible for us to read the smallest letters at incredible distances...' in his work De Iride.

Roger Bacon , an English Franciscan monk, documents the use of a telescope in his treatise Opus Majus, using terms very similar to his mentor, Robert Grosseteste.

Witelo , a Polish monk, writes Perspectiva - 'Optics' incorporating much of Kitab al-Manazir.

Florentine manuscript documents the use of lenses to correct the vision of the elderly. Florence will become the dominant center for lens manufacture in Europe for the next few hundred years. The name lens was probably derived around this time, because of similarity of its shape with the lentil bean (ventri lenticche).

From 1300 onwards concave mirrors similar to makeup or shaving mirrors used to aid in reading as an alternative to reading glasses.

Some time in the latter half of the 15th century, lensmakers develop technique to produce concave lenses. By this point, everything was in place to create both Keplerian and Galilean telescopes.

Leonardo da Vinci in Codex Arundul describes using a primitive reflecting telescope (based on a concave mirror) for astronomical purposes.

... in order to observe the nature of the planets, open the roof and bring the image of a single planet onto the base of a concave mirror. The image of the planet reflected by the base will show the surface of the planet much magnified.

Leonardo da Vinci in Codex Atlanticus mentions use of lenses to view the Moon.

...making glasses to see the Moon enlarged.

1520-1559 - Thomas Digges has described how his father, English mathematician and surveyor Leonard Digges, had built a 'perspective glass' which enabled the user to see small objects from very far away.

Girolamo Fracastoro, an Italian professor, poet and personal physician of the the pope suggests combining lenses to produce a telescopic effect in his work,Homocentricorum Seu de Stellis Liber Unus

Various Italian scientists (Benedetti, Barbaro, della Porta) experiment with optical projection systems based on various combinations of camera obscura, biconvex lenses, and concave mirrors. This would have required skilled production of lenses and concave mirrors.

In Le Api (1539), Giovanni Rucellai, Italian poet and cousin of the pope, describes the use of concave mirrors to magnify insects. This may have been the first dissecting microscope. This and da Vinci's reflector demonstrates that the practical application of mirrors for magnification was recognized well before the seventeenth century.

In Natural Magic, della Porta discusses telescopic and optical projection devices consisting of camera obscura, biconvex lenses, and a concave mirrors that could be used to project images. The passage below describes a telescopic device.

With a Concave Lenticular you shall see small things afar off very clearly. With a Convex Lenticular , things nearer to be greater, but more obscurely. If you know how to fit them both together, you shall see both things afar off, and things near hand, both greater and clearly.

Hans Lippershey, a Dutch lensmaker, and other Dutch lensmakers Jacob Metius and Zacharias Janssen ) engage in patent fight over the Galilean telescope design (convex objective and concave ocular). Patent denied because of prior art.

Galileo Galilei creates an improved version of the telescope based only on reports of the Dutch instruments. His improvements resulted in telescopes of 20 power. Telescopes with a convex objective and a concave eyepiece are known as 'Galilean' even though several described and used this design before him.

Christoph Scheiner, a Jesuit priest, constructs first modern astronomical telescope based on Kepler's design laid out in the Dioptrice (1611)

Niccolo Zucchi, a Jesuit priest, constructs a reflecting telescope using a lens and a borrowed mirror. First documented use of a combination of lenses and mirrors to make celestial and terrestrial observations.

While in the service of Archduke Maximilian of Tyrol, Christoph Scheiner, the Jesuit scientist, builds first modern terrestrial telescope. Scheiner had presented Maximilian with a Keplerian telescope which inverted the final image. When Maximilian complained, Scheiner added a third lens to correct the image. Modern terrestrial telescopes based on this design use four lenses.See Jesuits and the Telescope

In Discourse on the Method and Essays, Rene Descartes, the great scientist and mathematician, publishes his work on reflection and refraction. Is the first European to publish Snell's Law.

Keplerian design used by Scheiner and others replaces Galilean design as dominant design used in the larger research telescopes. This dominance would continue until about 1900 when reflecting telescopes would start to dominate.

By 1650 Telescope technology had been spread around the world. In 1613, Portugese mariners bring first telescope to new world. Use of the telescope was mentioned in records of the battle of Guaxanduba, Brazil between the French and Portugese. In 1621, Johannes Schreck, a Jesuit, brings first telescope to China. See Jesuits and the Telescope. Jean Bourdon, an engineer in Quebec, records using a telescope given him by the Jesuits in 1646.

Christiaan Huygens produces his design for a compound eyepiece.

Scottish mathematician, James Gregory, describes a reflecting telescope with a perforated concave main mirror and convex secondary mirror. Marin Mersenne had proposed a similar design 30 years before.

Isaac Newton produces his own design of reflecting telescope using a paraboloid primary mirror and a flat diagonal secondary mirror.

Robert Hooke produces an experimental model to the Gregorian design.

John Hadley constructs the first working telescope to the Gregorian design.

James Short , a Scottish optician and astronomer, succeeds in producing high-quality telescopes to the Gregorian design.

Chester Moore Hall invents the achromatic lens which combines two different types of glass in a lens to reduce optical distortions.

John Dollond patents the achromatic lens and begins a successful company building telescopes using these achromatic lenses. There is some controversy over whether Dollond independently invented the achromatic lens or borrowed the idea from Chester Moore Hall.

Jesse Ramsden invents his eponymous eyepiece.

Ernst Abbe designs the first orthoscopic eyepiece.

George Willis Ritchey and Henri Chretien co-invent the Ritchey-Chretien telescope used in many, if not most of the largest astronomical telescopes.

Bernhard Schmidt invents the Schmidt Camera.

Dmitri Maksutov invents the Maksutov telescope.