The early telescopes as manufactured in the Netherlands are refracting. "The first known practical telescopes were invented in the Netherlands at the beginning of the 17th century, using glass lenses."
"The earliest recorded working telescopes were the refracting telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, and Jacob Metius of Alkmaar. "The Hague discussed the patent applications first of Hans Lipperhey of Middelburg, and then of Jacob Metius of Alkmaar... another citizen of Middelburg, Sacharias Janssen had a telescope at about the same time but was at the Frankfurt Fair where he tried to sell it"."
"Galileo always insisted that the ancients had telescopes."
"The Russians have found crystal lenses, perfectly spherical and of great precision, in ancient Egypt, during the African-dominated period."
"It is also only within recent years that the discovery of a seminal black kingdom in the Nile Valley, predating the Egyptian dynasties, has settled the question, once and for all, of the roots of classical Egyptian culture and technology (see Journal of African Civilizations, vol. 4, no. 2, November 1982)."
- 1 Astronomy
- 2 Minerals
- 3 Theoretical telescopes
- 4 Keplerian telescopes
- 5 Air telescopes
- 6 Possible telescopes
- 7 Armillary spheres
- 8 Sighting tubes
- 9 Dioptras
- 10 Camera obscura
- 11 Tubes
- 12 Sceptres
- 13 Spindles
- 14 Torches
- 15 Eyes
- 16 Early lenses
- 17 Hypotheses
- 18 See also
- 19 References
- 20 Further reading
- 21 External links
“For we can so shape transparent bodies, and arrange them in such a way with respect to our sight and objects of vision, that the rays will be reflected and bent in any direction we desire, and under any angle we wish, we may see the object near or at a distance … So we might also cause the sun, moon and stars in appearance to descend here below.”
"Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. ... Pure quartz, traditionally called rock crystal (sometimes called clear quartz), is colorless and transparent or translucent."
"Iceland spar, formerly known as Iceland crystal, is a transparent variety of calcite, or crystallized calcium carbonate" "It has been speculated that the sunstone (a different mineral than the gem-quality sunstone) mentioned in medieval Icelandic texts was Iceland spar and that Vikings used its light-polarizing property to tell the direction of the sun on cloudy days, for navigational purposes."
"A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality almost no gem-sized natural diamonds are absolutely perfect."
"c. 3500 B.C. Phoenicians cooking on sand discover glass."
"Natural glass has existed since the beginnings of time, formed when certain types of rocks melt as a result of high-temperature phenomena such as volcanic eruptions, lightning strikes or the impact of meteorites, and then cool and solidify rapidly. Stone-age man is believed to have used cutting tools made of obsidian (a natural glass of volcanic origin also known as hyalopsite, Iceland agate, or mountain mahogany) and tektites (naturally-formed glasses of extraterrestrial or other origin, also referred to as obsidianites)."
"According to the ancient-Roman historian Pliny (AD 23-79), Phoenician merchants transporting stone actually discovered glass (or rather became aware of its existence accidentally) in the region of Syria around 5000 BC [7,000 b2k]. Pliny tells how the merchants, after landing, rested cooking pots on blocks of nitrate placed by their fire. With the intense heat of the fire, the blocks eventually melted and mixed with the sand of the beach to form an opaque liquid."
"The earliest man-made glass objects, mainly non-transparent glass beads, are thought to date back to around 3500 BC, with finds in Egypt and Eastern Mesopotamia. In the third millennium, in central Mesopotamia, the basic raw materials of glass were being used principally to produce glazes on pots and vases. The discovery may have been coincidental, with calciferous sand finding its way into an overheated kiln and combining with soda to form a coloured glaze on the ceramics. It was then, above all, Phoenician merchants and sailors who spread this new art along the coasts of the Mediterranean."
Def. "[a] monocular optical instrument possessing magnification for observing distant objects" is called a telescope.
Def. "any instrument ... for observing distant objects" is called a telescope.
"From Latin telescopium, from Greek τηλεσκόπος (tēleskopos), far-seeing, from τῆλε (tēle, "afar") + σκοπέω (skopeō, "I look at)."
"The Keplerian Telescope, invented by Johannes Kepler in 1611, is an improvement on Galileo's design. It uses a [plano]convex lens as the eyepiece instead of Galileo's [double] concave one. The advantage of this arrangement is [that] the rays of light emerging from the eyepiece are converging. This allows for a much wider field of view and greater eye relief but the image for the viewer is inverted. Considerably higher magnifications can be reached with this design but to overcome aberrations the simple objective lens needs to have a very high [focal ratio] f-ratio".
"All refracting telescopes use the same principles. The combination of an objective lens 1 and some type of eyepiece 2 is used to gather more light than the human eye could collect on its own, focus it 5, and present the viewer with a brighter, clearer, and magnified virtual image 6."
At right is a woodcut illustration of a 45 m focal length Keplerian air, or aerial telescope built by Johannes Hevelius, "and even longer tubeless "aerial telescopes" were constructed".
"An aerial telescope is a type of very-long-focal-length refracting telescope built in the second half of the 17th century that did not use a tube. "After about 1675, therefore, astronomers did away with the telescope tube. The objective was mounted on a building or pole by means of a ball-joint and aimed by means of a string..." Instead, the objective was mounted on a pole, tree, tower, building or other structure on a swivel ball-joint. The observer stood on the ground and held the eyepiece, which was connected to the objective by a string or connecting rod. By holding the string tight and maneuvering the eyepiece, the observer could aim the telescope at objects in the sky. The idea for this type of telescope may have originated in the late 17th century with the Dutch mathematician, astronomer and physicist Christiaan Huygens and his brother Constantijn Huygens, Jr., though it is not clear that they invented it."
An even simpler air telescope is shown in the second image at left. To have only an air telescope, an ancient needs lenses. The ones in the schematic are called planoconvex. Convex on one side towards the target and planar on the viewing side.
The image at right is a painting by artist Giorgio Vasari (1511–1574). Behind and above the main focus on Cronus (Saturn) castrating Uranus (the Greek sky god before Zeus) is what appears to be "some kind of Armillary sphere". Specifically, the "[w]hole thing is some kind of Armillary sphere".
Even more than that is an object angled slightly upward (right to left) that appears to be pointed at or above the large metallic ring. This object seems to be painted as if it extends through the top hole of the armillary sphere. At the upper left end of the object is an embellished end piece that may have a lens (objective lens) or piece of material the diameter of which matches that of the tube behind the embellishment. The midsection appears to taper to a smaller diameter near the right end. The right end has an even smaller piece attached or inserted that looks like an eyepiece lens holder. This tubular object seems to be receiving hands in the air praise from two people to its left. The armillary sphere may be tilted ~23 1/2°.
The tubular object bares a striking resemblance to a telescope. The image taken as a whole suggests an interaction between Cronus and Uranus as observed near the plane of the ecliptic by someone through a telescope.
Another suggestion: "It would be the sceptre, the symbolic attribute of the ruler of the deities and of the universe. It was an attribute of Uranus and is about to pass to Cronus. The nature of a sceptre as a phallic symbol seems especially obvious in the context of this painting. The ruling god and owner of the sceptre during a given mythical era is also the main progenitor of that era. (Thus mirroring an alpha male in primate and some other animal societies.)". Bold added.
The Castration of Uranus is apparently a fresco by Vasari & Cristofano Gherardi (c. 1560, Sala di Cosimo I, Palazzo Vecchio, Florence).
"This painting is new to me, I must admit, and I have no idea what the object is that you refer to. It looks as though it might be [a] spindle of some kind."
"I don't think it really looks like a telescope, apart from anything else it would hardly fit into the iconography of the mutilation of Uranus by Saturn. Having looked at other paintings relating to this myth, I think your so-called spindle is more likely a torch that has gone out in the chaos of the scene depicted - Maybe a metaphor for upsetting the light of the Sun or similar, who knows."
The frontispiece from Johannes Kepler's Rudolphine Tables appears to have a telescope drawn in on the upper roof extension on the left side. While this would be no surprise if the drawing dates from after 1609, as suspected, it would be a surprise if this drawing dates from the 1500's.
"Richer wrote about another of Gerbert's last armillary sphere, which had sighting tubes fixed on the axis of the hollow sphere that could observe the constellations, the forms of which he hung on iron and copper wires. This armillary sphere was also described by Gerbert in a letter to his colleague Constantine. Gerbert instructed Constantine that, if doubtful of the position of the pole star, he should fix the sighting tube of the armillary sphere into position to view the star he suspected was it, and if the star did not move out of sight, it was thus the pole star. Furthermore, Gerbert instructed Constantine that the north pole could be measured with the upper and lower sighting tubes, the Arctic Circle through another tube, the Tropic of Cancer through another tube, the equator through another tube, and the Tropic of Capricorn through another tube."
The first two images at the right dating from 1480 and 1547 show the sphere without sighting tubes or any device for observing astronomical objects.
The first two images at the left show spheres dating to after 1608 and the Dutch invention of the telescope.
It appears to be the case that armillary spheres are often displayed without any attachment for viewing such as a sighting tube or telescope.
Of the some 458 images of armillary spheres in commons, only the Vasari painting shows a sighting tube or telescope of any kind within or attached to the sphere.
"On the use of the sighting tube to fix the position of the pole star, Shen Kuo wrote:"
Before Han times it was believed that the pole star was in the center of the sky, so it was called Jixing (Summit star). Zi Geng(-zhi) found out with the help of the sighting tube that the point in the sky which really does not move was a little more than 1 degree away from the summit star. In the Xining reign-period (1068-1077) I accepted the order of the emperor to take charge of the Bureau of the Calendar. I then tried to find the true pole by means of the tube. On the very first night I noticed that the star which could be seen through the tube moved after a while outside the field of view. I realized, therefore, that the tube was too small, so I increased the size of the tube by stages. After three months' trials I adjusted it so that the star would go round and round within the field of view without disappearing. In this way I found that the pole star was distant from the true pole somewhat more than 3 degrees. We used to make the diagrams of the field, plotting the positions of the star from the time when it entered the field of view, observing after nightfall, at midnight, and early in the morning before dawn. Two hundred of such diagrams showed that the 'pole star' was really a circumpolar star. And this I stated in my detailed report to the emperor.
"A dioptra [the image at the right] is a classical astronomical and surveying instrument, dating from the 3rd century BCE. The dioptra was a sighting tube or, alternatively, a rod with a sight at both ends, attached to a stand. If fitted with protractors, it could be used to measure angles."
"Greek astronomers used the dioptra to measure the positions of stars; both Euclid and Geminus refer to the dioptra in their astronomical works."
Girolamo Cardano (1501-1576) made "a camera obscura with a diverting spectacle ... appears ... to have initiated the use of a convex lens in the aperture."
"There are indeed ancient tablets that mention astronomers' lenses supported by a golden tube to enlarge the pupil, and in Nineveh a rock crystal lens was found (Pettinato 1998). Maybe one day a new archaeological excavation will find a Babylonian telescope for the first time."
The sceptre imaged at the right is a piece of the Portuguese crown jewels. Note that the image is vertical as is the sceptre.
The image at the left shows a sceptre dated to before 1380.
A key point is that the sceptres both display an object setting above and removed from the shaft of the septre which is either tapered or cylindrical.
The object in the Uranus/Saturn painting from about 1560 does not have an object displayed on top of the sceptre but shows an object closely resembling an objective lens inside its housing.
The second image on the right shows that earlier scepters, or perhaps walking sticks were lengthy, approximately two-thirds a person's height. The ornamentation at the scepters upper end varied greatly as the sculpture at the second left shows.
More recent scepters such as the one shown at third right and third left are sword-like.
The fourth image at the right demonstrates that scepters may be much shorter. The scepter is in the statue's right hand.
On the right is a photograph of an apparently 16th century artwork which shows a blazing torch immediately behind the Pope.
The torch painted in second image down the right is much longer and narrower than the one higher or lower on the left.
The second image down on the left shows only the torch from Michele Rocca's "Angelica and Medoro" dated to "between circa 1720 and circa 1750".
"Old Kingdom Egyptian statues from the first to the sixth dynasties had lenses placed in their eyes." "The thickness of the lenses was not intended to duplicate the thickness of the real human eye, but rather to create an effect so that the eye follows the person passing by when looked from other angles." "[T]he illusion of the following eye technique."
"The Archaic or Early Dynastic Period of Egypt immediately follows the unification of Lower and Upper Egypt c. 3100 BC. It [is] generally taken to include the First and Second Dynasties, lasting from the Protodynastic Period of Egypt until about 2686 BC, or the beginning of the Old Kingdom."
The eyes of these statues contain rock-crystals. "These are probably the oldest portrait statues in the world. These people who sit before us side by colored to the life, fresh and glowing as the day they gave the artist his last sitting lived at a time when the great pyramids were not yet built and at a date which is variously calculated as from about 4,000 to 6,300 years from the present day. The princess wears her hair precisely as it is still worn in Nubia and her necklace is of a pattern still favored. The eyes of both statues are inserted. The eyeball which is set in an eyelid of bronze, is made of opaque white quartz with an iris of rock-crystal enclosing a pupil of some kind of brilliant metal. This treatment gives to the eyes a look of intelligence which is almost appalling." Amelia B. Edwards "These incomparable statues are most expressive and stand in vitality to the works of any later age in Egypt. They were found in the tomb chamber- Ra-Ho-tep is entitled a royal son [probably of Seneferu]- The signs carved in these tombs are among the earliest known. Instead of full-length burial with coffins, head rests, vases, and provision for a future life, the more usual method of burial at Medum is lying on the left side with the knees drawn up facing the east and without vases or other objects, showing a diversity of beliefs and probably of races." W.M. Flinders Petrie.
"The composition of these eyes is a lens of polished rock crystal (either alpha silica or fused silica, formerly known as cystalline quartz and fused quartz which had a convex front surface and a near hemispherical concave ground pupil surface in a flat iris plane (normally covered with resin) at the rear of the lens."
"The Prehistory of Egypt spans the period of earliest human settlement to the beginning of the Early Dynastic Period of Egypt in ca. 3100 BC, starting with King Menes/Narmer."
"The Predynastic Period is traditionally equivalent to the Neolithic period, beginning ca. 6000 BC and including the Protodynastic Period (Naqada III)."
"There are now 23 ancient lenses on display in the Archaeological Museum at Herakleion and many more are in storage there. They are also made of rock crystal and are of optical quality, with generated plano-convex surfaces."
There is more about lenses more recently from Visby, Gotland. "What intrigues the researchers is that the lenses are of such high quality that they could have been used to make a telescope some 500 years before the first known crude telescopes were constructed in Europe in the last few years of the 16th century." "Made from rock-crystal, the lenses have an accurate shape that betrays the work of a master craftsman. The best example of the lenses measures 50 mm (2 inches) in diameter and 30 mm (1 inch) thick at its centre." "The [Visby] Gotland crystals provide the first evidence that sophisticated lens-making techniques were being used by craftsmen over a 1,000 years ago."
"If one Italian scientist is correct then the telescope was not invented sometime in the 16th century by Dutch spectacle makers, but by ancient Assyrian astronomers nearly three thousand years earlier. According to Professor Giovanni Pettinato of the University of Rome, a rock crystal lens, currently on show in the British museum, could rewrite the history of science. He believes that it could explain why the ancient Assyrians knew so much about astronomy."
|Name (or identification)||Discovery period||Location||Approximate date||Source unless noted otherwise|
|Egyptian lenses||IV/V Dynasties||Egypt, eyes in funerary statues||2620-2400 BC|||
|Evans lenses (plano-convex)||Middle Minoan IIIB||Temple Repositories at Knossos, along with a "royal Draught Board" with ivory and crystal inlays backed with silver foil||1640-1600 BC, Minoan civilization||A. Evans, The Palace of Minos I (London 1921) 469-72; cf. the eye of the steatite bull's-head rhyton from the Little Palace at Knossos: Evans, The Tomb of the Double Axes etc (London 1914) 82.|
|"Three bossed crystal discs" (plano-convex)||Late Minoan II-IIIA||Mavrospelio cemetery||1425-1340 BC||E. J. Forsdyke, "The Mavro Spelio Cemetery at Knossos," BSA 28 (1926-1927) 243-96, esp. 288.|
|Artemision lenses (plano-concave)||Archaic levels||the Artemision of Ephesos||3300-1200 BC||D.G. Hogarth, Excavations at Ephesus: The Archaic Artemisia (London 1908) 210-11, pl. 46.|
|Schliemann lenses (plano-convex)||Troy||Troy||1334-1184 BC||V. Tolstikov and M. Treister, The Gold of Troy: Searching for Homer's Fabled City (London 1996) nos. 176-216, 230.|
|Nimrud lens (plano-convex)||Neo-Assyrian||North West Palace, Room AB||750–710 BC||Austen Henry Layard at the Assyrian palace of Nimrud, in modern-day Iraq.|
|Roman London lens (fragmentary biconvex glass lens of light green color)||Roman London||Roman London||43-50 AD||H. Syer Cuming, "On Spectacles," The Journal of the British Archaeological Association 11 (1855) 144-49.|
|Pompeii lens (plano-convex)||excavations of the Via Stabia||"House of the Engraver"||79 AD||E. Gerspach, L'art de la verrerie (Paris 1885) 41-42.|
|four rock-crystal lentoids (plano-convex)||the historical period||Amathous||Temple of Aphrodite||M.-E Boussac in P. Aupert and A. Hermary, "Travaux de l'Ecole franlaise i Amathonte en 1979," BCH 104 (1980) 809, fig. 12; Aupert and Hermary, "Amathonte: Rapport préliminaire (1975-1979)," RDAC 1980, 237, pl. 32.6|
|Sakellarakis lenses (plano-convex)||historical period||Idaean Cave||historical period|||
- The ancients may have used air or aerial telescopes.
- "Telescope, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 14, 2012. Retrieved 2012-09-17.
- galileo.rice.edu The Galileo Project > Science > The Telescope by Al Van Helden
- Ivan Van Sertima (2010). Ivan Van Sertima. ed. The Lost Sciences of Africa: An Overview, In: Blacks in Science: Ancient and Modern. Pscataway, New Jersey, USA: Transaction Publishers. pp. 5-26. ISBN 978-0-87855-941-1. http://books.google.com/books?hl=en&lr=&id=RqOz55ZBfdkC&oi=fnd&pg=PA5&ots=MJBIE2cQ8v&sig=N3hYQoGoqp3ShdiSX1TZppxe05E. Retrieved 2012-10-04.
- Roger Bacon (1214-94). Opus Majus. Astronomy Trek. http://www.astronomytrek.com/ancient-telescopes-and-lenses/. Retrieved 2014-06-06.
- "Quartz, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. August 29, 2012. Retrieved 2012-09-03.
- "Iceland spar, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. August 25, 2012. Retrieved 2012-09-03.
- The Viking Sunstone, from Polarization.net. Retrieved February 8, 2007.
- Leif K. Karlsen 2003. Secrets of the Viking Navigators. One Earth Press. ISBN 978-0-9721515-0-4 pp. 220
- "Diamond color, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. August 17, 2012. Retrieved 2012-09-03.
- Larry Brown (2005). "An early history of the telescope. From 3500 B.C. until about 1900 A.D.". Antique Telescopes. Retrieved 2012-04-08.
- Infoserv (April 15, 2011). "A Brief History of Glass". Artenergy Publishing S.r.l. Retrieved 2014-06-06.
- "telescope, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 25 May 2014. Retrieved 2014-06-06.
- AH Tunnacliffe, JG Hirst (1996). Optics. Kent, England. pp. 233–7. ISBN 0-900099-15-1.
- "Refracting telescope, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. July 7, 2012. Retrieved 2012-07-07.
- The Galileo Project > Science > The Telescope
- Henry C. King (2003). "The history of the telescope". ISBN 978-0-486-43265-6.
- "The First Telescopes". Cosmic Journey: A History of Scientific Cosmology. Center for History of Physics, a Division of the American Institute of Physics.
- A. E. Bell. Ph.D., M.Sc. "Christian Huygens and the Development of Science in the Seventeenth Century".
- "Aerial telescope, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. August 16, 2012. Retrieved 2012-10-08.
- AnonMoos (October 8, 2012). "Image in Vasari painting, In: Wikimedia Commons". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2012-10-08.
- Asclepias (October 8, 2012). "Image in Vasari painting, In: Wikimedia Commons". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2012-10-16.
- "Giorgio Vasari, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. October 8, 2012. Retrieved 2012-10-08.
- Ian Ridpath (1 November 2014). "Re: Early telescopes". Yahoo!. Retrieved 2014-11-03.
- Kevin Johnson (3 November 2014). "Re: Early telescopes". Yahoo!. Retrieved 2014-11-03.
- S. Jim Tester (1987). A History of Western Astrology. Rochester: Boydell & Brewer. ISBN 0-85115-446-8.
- Oscar G. Darlington (1947). "Gerbert, the Teacher". American Historical Review 52 (3): 456–76.
- "Pope Sylvester II, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 25, 2012. Retrieved 2012-10-08.
- "Dream Pool Essays, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. July 15, 2012. Retrieved 2012-10-08.
- Needham, Joseph (1986). Science and Civilization in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth. Taipei: Caves Books, Ltd.
- "Dioptra, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. October 1, 2012. Retrieved 2012-10-08.
- Paul T. Burns (1990). "The History of The Discovery of Cinematography - 1400 - 1599". Planetel Communications. Retrieved 2012-10-08.
- Giulio Magli (2009). When the method is lacking, In: Mysteries and Discoveries of Archaeoastronomy from Giza to Easter Island. Rome, Italy: Copernicus Books. pp. 97-116. doi:10.1007/978-0-387-76566-2_5. ISBN 978-0-387-76564-8. http://www.springerlink.com/content/w2q6g0q252221k0u/fulltext.pdf. Retrieved 2011-10-15.
- Koot van Wyk (July 8, 2010). "Lenses and Telescopes in the Ancient Near East and the Bible". Retrieved 2012-10-04.
- Ian Shaw, ed (2000). The Oxford History of Ancient Egypt. Oxford University Press. p. 479. ISBN 0-19-815034-2.
- "Early Dynastic Period of Egypt, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 27, 2012. Retrieved 2012-10-04.
- "File:Prince Ra-Hotep and Princess Nefer-T (cropped).jpg, In: Wikimedia Commons". San Francisco, California: Wikimedia Foundation, Inc. December 22, 2011. Retrieved 2012-10-04.
- Al Berens (2001). "Remarkable Old Kingdom Lenses and the Illusion of the Following Eye". Comcast. Retrieved 2012-10-04.
- "Prehistoric Egypt, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. October 4, 2012. Retrieved 2012-10-04.
- Dimitris Plantzos (July 1997). "Crystals and Lenses in the Graeco-Roman World". American Journal of Archaeology 101 (3): 451-64. http://www.hist-arch.uoi.gr/prosopiko/plantzos/Crystals.pdf. Retrieved 2011-10-17.
- Austen Henry Layard (1853). Discoveries in the ruins of Nineveh and Babylon: with travels in Armenia. G.P. Putnam and Co. pp. 197–8,674. http://books.google.com/?id=1KITAAAAYAAJ&pg=PA674&dq=british+museum+lens+layard#v=onepage&q=lens&f=false.
- D. Brewster (1852). "On an account of a rock-crystal lens and decomposed glass found in Niniveh" (in German). Die Fortschritte der Physik (Deutsche Physikalische Gesellschaft). http://books.google.com/?id=bHwEAAAAYAAJ&pg=RA1-PA355.
- "Nimrud lens, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. September 14, 2012. Retrieved 2012-10-03.
- George Sines and Yannis A. Sakellarakis (April 1987). "Lenses in antiquity". American Journal of Archaeology 91 (2): 191-6. http://www.jstor.org/stable/10.2307/505216. Retrieved 2012-10-03.
- David Whitehouse (April 5, 2000). "Did the Vikings make a telescope?". BBC News. Retrieved 2012-10-03.
- Jay M. Enoch, Vasudevan Lakshminarayanan (March 2000). "Duplication of unique optical effects of ancient Egyptian lenses from the IV/V Dynasties: lenses fabricated ca 2620–2400 BC or roughly 4600 years ago". Ophthalmic and Physiological Optics 20 (2): 126-30. doi:10.1046/j.1475-1313.2000.00496.x. http://onlinelibrary.wiley.com/doi/10.1046/j.1475-1313.2000.00496.x/abstract. Retrieved 2012-10-03.
- David Whitehouse (July 1, 1999). "World's oldest telescope?". BBC News. Retrieved May 10, 2008.
- An early history of the telescope - From 3500 B.C. until about 1900 A.D.
- The Prehistory of the Invention of the Telescope
- Dimitris Plantzos (July 1997). "Crystals and Lenses in the Graeco-Roman World". American Journal of Archaeology 101 (3): 451-64. http://www.hist-arch.uoi.gr/prosopiko/plantzos/Crystals.pdf. Retrieved 2011-10-17.
- African Journals Online
- Bing Advanced search
- Google Books
- Google scholar Advanced Scholar Search
- International Astronomical Union
- Lycos search
- NASA/IPAC Extragalactic Database - NED
- NASA's National Space Science Data Center.
- NCBI All Databases Search
- Office of Scientific & Technical Information
- Questia - The Online Library of Books and Journals
- SAGE journals online
- The SAO/NASA Astrophysics Data System
- Scirus for scientific information only advanced search
- SDSS Quick Look tool: SkyServer
- SIMBAD Astronomical Database
- Spacecraft Query at NASA.
- Taylor & Francis Online
- Universal coordinate converter
- Wiley Online Library Advanced Search
- Yahoo Advanced Web Search
Learn more about Telescope