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Damian Burrin wrote:
what was the first telescope? Galileo invented the telescope in 1609 it was a refractor, Newton intented the reflector scope but i forget when. That is wrong in every important respect: * The first telescope, a catadioptric, was probably invented by Leonard Digges, before 1561 (which is the earliest mention of it). * Thomas Harriot, a tutor of Walter Raleigh, drew a telescopic map of the Moon in 1608, before Galileo obtained his first telescope. * The refractor was made by Hans Lippershey in 1608 * The reflector was invented by James Gregory in 1663 * Newton made his reflector in 1668 Best, Stephen Remove footfrommouth to reply -- + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books + + (N51.162 E0.995) | http://astunit.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + |
#2
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The first telescope?
what was the first telescope? or is it unknown for sure. was it a refractor?
presumably its not in existance now. |
#3
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what was the first telescope?
Galileo invented the telescope in 1609 it was a refractor, Newton intented the reflector scope but i forget when. Damian -- Damian Burrin UKRA 1159 Level 2 RSO EARS 1115 http://www.ukrocketry.com http://www.larf-rocketry.co.uk "simon.coombs3" wrote in message ... what was the first telescope? or is it unknown for sure. was it a refractor? presumably its not in existance now. |
#4
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In message , Stephen Tonkin
writes Damian Burrin wrote: what was the first telescope? Galileo invented the telescope in 1609 it was a refractor, Newton intented the reflector scope but i forget when. That is wrong in every important respect: Good enough for GCSE in Astronomy, then. |
#5
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"simon.coombs3" wrote in message ... what was the first telescope? or is it unknown for sure. was it a refractor? presumably its not in existance now. As well as this piece from NS I seem to remember archaeoligists finding a pair of felspar slivers in close proximity at a Viking site. The speculation was they would have been housed in a wooden tube , mutually rotatable and acting as a solar polariscope for guaging time at sea even when overcast. New Scientist vol 160 issue 2159 - 07 November 1998, page 25 Vikings were surprisingly well focused STUDIES of Viking lenses suggest their makers could have taught modern optometrists a thing or two. Quartz lenses made around one thousand years ago have optical properties that match modern standards. Aspheric lenses, which have an elliptical shape, are commonly used in spectacles and cameras. The equations describing their optical properties are thought to have been devised by the French philosopher and mathematician René Descartes in the 17th century. But he could not find anyone skilful enough to make one. Yet now it seems the Vikings were making them hundreds of years earlier. Optics specialists led by Olaf Schmidt of the University of Applied Science in Aalen, Germany, have studied Viking lenses from museums in Munich and Sweden. They found their shapes closely matched an ellipse. The optical qualities of some of the best examples were comparable to modern lenses. "If you look at the shape of the lenses they are remarkably smooth," says Schmidt. Schmidt believes the lenses were made on a simple lathe and used for focusing sunlight to light fires and cauterise wounds. How Viking craftsmen discovered the optimum shape remains a mystery. "I think it's very unlikely they understood the mathematics of the lenses," says John Bell, editor of Opto & Laser Europe. Duncan Graham-Rowe source: http://archive.newscientist.com/secu...1&id=mg1602159 3.900 My conjecture is you don't need carefully crafted lenses to start fires. Humour of the streets http://www.divdev.fsnet.co.uk/graff.htm |
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* The first telescope, a catadioptric, was probably invented by Digges,
before 1561 From Nineplanets.org English scholars Robert Recorde (1551) and Leonard Digges (1571) refer to use of "perspective glasses" to view distant objects, while Digges discusses mirrors being used similarly. William Bourne (1585) and Giambattista Della Porta (1589) claimed to have discovered a way to use two lenses to view distant objects, but neither manufactured a telescope. Controversy over the Invention of the Refracting Telescope Dutch spectacle maker Hans Lippershay filed a patent application in Holland on October 2, 1608, requesting exclusive rights to make and distribute "an instrument for seeing at a distance", consisting of a weak positive objective lens and a strong negative eyepiece. Lippershay constructed a telescope on request and was tested successfully; he received an initial contract for construction of up to three instruments. Dutch spectacle maker Jacob Adriaanzoon filed a counterpetition, claiming he had constructed a telescope of power equal to Lippershay's and would construct one if he were paid to do it. Given the success in dealing with Lippershay, the Dutch authorities declined to pay for the construction. Dutch spectacle maker Zacharias Jansen claimed to have invented the telescope prior to Lippershay and that the latter should not be granted an exclusive manufacturing patent. Despite a lack of evidence for prior invention from Adriaanzoon and Jansen, the Dutch government decided the issue too confused and refused to grant Lippershay's application. -- Damian Burrin UKRA 1159 Level 2 RSO EARS 1115 http://www.ukrocketry.com http://www.larf-rocketry.co.uk "Stephen Tonkin" wrote in message ... Damian Burrin wrote: what was the first telescope? Galileo invented the telescope in 1609 it was a refractor, Newton intented the reflector scope but i forget when. That is wrong in every important respect: * The first telescope, a catadioptric, was probably invented by Leonard Digges, before 1561 (which is the earliest mention of it). * Thomas Harriot, a tutor of Walter Raleigh, drew a telescopic map of the Moon in 1608, before Galileo obtained his first telescope. * The refractor was made by Hans Lippershey in 1608 * The reflector was invented by James Gregory in 1663 * Newton made his reflector in 1668 Best, Stephen Remove footfrommouth to reply -- + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books + + (N51.162 E0.995) | http://astunit.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + |
#7
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I'm sure this was a question on QI, with Galileo being an 'obvious' answer
Larry "Stephen Tonkin" wrote in message ... Damian Burrin wrote: what was the first telescope? Galileo invented the telescope in 1609 it was a refractor, Newton intented the reflector scope but i forget when. That is wrong in every important respect: * The first telescope, a catadioptric, was probably invented by Leonard Digges, before 1561 (which is the earliest mention of it). * Thomas Harriot, a tutor of Walter Raleigh, drew a telescopic map of the Moon in 1608, before Galileo obtained his first telescope. * The refractor was made by Hans Lippershey in 1608 * The reflector was invented by James Gregory in 1663 * Newton made his reflector in 1668 Best, Stephen Remove footfrommouth to reply -- + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books + + (N51.162 E0.995) | http://astunit.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + |
#8
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Very interesting. My view is that just as the likes of Ross and Herschel
checked the accuracy of their optics pragmatically, by seeing how good the image was, the vikings in your story might have done likewise. Victorian and before optics are generally appalling when tested with modern equipment, but there is no question that they achieved better than spherical approximations. Brian "N Cook" wrote in message news "simon.coombs3" wrote in message ... what was the first telescope? or is it unknown for sure. was it a refractor? presumably its not in existance now. As well as this piece from NS I seem to remember archaeoligists finding a pair of felspar slivers in close proximity at a Viking site. The speculation was they would have been housed in a wooden tube , mutually rotatable and acting as a solar polariscope for guaging time at sea even when overcast. New Scientist vol 160 issue 2159 - 07 November 1998, page 25 Vikings were surprisingly well focused STUDIES of Viking lenses suggest their makers could have taught modern optometrists a thing or two. Quartz lenses made around one thousand years ago have optical properties that match modern standards. Aspheric lenses, which have an elliptical shape, are commonly used in spectacles and cameras. The equations describing their optical properties are thought to have been devised by the French philosopher and mathematician René Descartes in the 17th century. But he could not find anyone skilful enough to make one. Yet now it seems the Vikings were making them hundreds of years earlier. Optics specialists led by Olaf Schmidt of the University of Applied Science in Aalen, Germany, have studied Viking lenses from museums in Munich and Sweden. They found their shapes closely matched an ellipse. The optical qualities of some of the best examples were comparable to modern lenses. "If you look at the shape of the lenses they are remarkably smooth," says Schmidt. Schmidt believes the lenses were made on a simple lathe and used for focusing sunlight to light fires and cauterise wounds. How Viking craftsmen discovered the optimum shape remains a mystery. "I think it's very unlikely they understood the mathematics of the lenses," says John Bell, editor of Opto & Laser Europe. Duncan Graham-Rowe source: http://archive.newscientist.com/secu...1&id=mg1602159 3.900 My conjecture is you don't need carefully crafted lenses to start fires. Humour of the streets http://www.divdev.fsnet.co.uk/graff.htm --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.716 / Virus Database: 472 - Release Date: 05/07/04 |
#9
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"Brian" wrote in message ...
Very interesting. My view is that just as the likes of Ross and Herschel checked the accuracy of their optics pragmatically, by seeing how good the image was, the vikings in your story might have done likewise. Victorian and before optics are generally appalling when tested with modern equipment, but there is no question that they achieved better than spherical approximations. Brian I was a bit rushed when I extracted the piece from the NS archive and posted. I meant to also say that for cauterising, they would have used a red-hot poker or hot tar - focusing the sun is a bit far-fetched. The ther point is the archaeological context. I cannot find citation of the felspar cross- polarizers but they were found close together suggesting a pair used together. A lot depends on how the Viking lenses were found; single, pairs, pair lad out as specs or pairs laid out as scope. |
#10
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"N Cook" wrote in message ...
STUDIES of Viking lenses suggest their makers could have taught modern optometrists a thing or two. Quartz lenses made around one thousand years ago have optical properties that match modern standards. Yet now it seems the Vikings were making them hundreds of years earlier. Optics specialists led by Olaf Schmidt of the University of Applied Science in Aalen, Germany, have studied Viking lenses from museums in Munich and Sweden. They found their shapes closely matched an ellipse. The optical qualities of some of the best examples were comparable to modern lenses. "If you look at the shape of the lenses they are remarkably smooth," says Schmidt. Schmidt believes the lenses were made on a simple lathe and used for focusing sunlight to light fires and cauterise wounds. How Viking craftsmen discovered the optimum shape remains a mystery. "I think it's very unlikely they understood the mathematics of the lenses," says John Bell, editor of Opto & Laser Europe. Duncan Graham-Rowe The Vikings had a range or remarkable skills. Not least their shipbuilding and jewellery. The skills and materials involved in working & polishing gold and silver cannot have been lost on these early opticians. Their raw materails may have come from volcanic Iceland or Norway. A vertical "potters wheel" or pole lathe using resin to hold the lens to a rotating device is not rocket science. The use of natural tar or resins as a polishing lap with whatever polishing media was available would no doubt provide a high polish. Cloth (or paper?) would also function as polishing tool coverings. It may be that they used very long, slow polishing methods which contributed to the high polish and asphericity. Given enough time the skills would be raised to a high standard. There was some suggestion that the lenses may have come from Arabia. Though I can't see why that should be necessary. Given the extraordinary skills shown by the Vikings in other fields. Localised polishing can be achieved by degrees of overhang. Or stroking of polishing tools in well rehearsed movements. Such localised polishing could be deliberate or quite accidental. I am surprised to hear that Victorian lenses were so poor. I had the pleasure of watching elderly optical workers with decades of experience. Shaping and polishing unusual spectacle lenses on simple vertical spindles. The chosen cast-iron tool rotated on the tapered spindle in a round vertical drum. Which collected the abrasive that flew off the work. A hand-controlled over-arm with an adjustable downward-pointing pin held the back of the lens via a lacquered or pitched on back plate. Which allowed the lens to spin freely on the tool under the pin. The skills of these men had to be seen to be appreciated. No lens gave them a moment's pause. Their movements were totally instinctive whether the lens was a small convex "pebble", completely flat or as deep as an egg cup. The polish achieved was very transparent compared with the machine-made lenses using the same paper polishing pads and cerium oxide. There is no reason why a Viking craftsman with a similar machine (however crude) could not develop a polishing routine over many years which offered a near perfect finished product. Any asphericity may have been a direct result of the methods, tools or materials used. It may be that the natural crystals they used in lens making had differing hardness. Depending on the axis of crystal being polished. Using a crude analogy: If the crystal were a piece of wood: It is possible that the "grain" of the material was always chosen to be at right angles to the lens axis. Or the crystal was always formed in such a way that a lens would always be made from the largest diameter. Which always coincided with the crystal's natural grain orientation. The centre of the lens might have different qualities to the "shoulders" which would be "end grain" (in the crude 'wood' analogy) The centre of the lens would polish away relative to the harder-to-polish "shoulders" & edges. Resulting automatically in an elipsoid of revolution. But I have no experience whatsoever of the materials involved and may be quite mistaken as to a "grain" being present in these rock crystals. Chris.B |
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