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Message: <blockquote data-quote="Gijs van Ginkel" data-source="post: 3207733" data-attributes="member: 82596">Binastro, post 24,Of course it is interesting to know what we believe, but historians have put a lot of effort in the investigation of lensmaking and the invention of the telescope. In the literature I cited no proof was presented that Digges made a telescope, allthough he has suggested a design for it  and I also did not find evidence that his telescope ideas were kept a secret for military purposes. That is important, since the Dutch authoriteis of 1608 immediately showed Lipperhey's telescope to the military of that time and it is written that the Dutch general of that time, Maurits showed it to his Spanish opponent, who was struck by its military potential. The binocular constructed by Lipperhey did not arrive from heaven, but was constructed because the Dutch authorities asked him to construct one and that was, considering that no binoculars were known in 1608, quite a challenge and Lipperhey succeeded, since he made in some months after preentation of his telescope three of them. If you study the historic literature of that time, you will see that as soon as Lipperhey had shown its invention, the news spread very rapidly through Europe and it is now well known how that came about: a short international newspaper had some space letft and that was filled with the news of the telescope invention in The Netherlands. The question is how was it possible that Lipperhey was able to construct usable telescopes/binoculars and how was it possiblel that other lensmakers were able to copy that so quickly. Rolf Villach has answered that question in a very elegant way by investigating lenses of telescopes from the 1600 hundreds and the answer was in the end very simple: Lipperhey as a spectacle maker was able to make good lenses (good for that time in history) but the combination of two of such lenses did not yield a usable telescope. So what Lipperhey did: he constructed a diaphragm around the lens so the optical errors were filtered out to a great extent and in that simple way he obtained a usable telescope. Villach and others also explained why Digges etc. were not able to construct usable telescopes, because they did not have a supply of lenses they could choose from to construct with trial and error a usable telescope. The invention of spectacles and the availability of good quality glass has  therefore been of great  importance for the invention of the telescope. Studies form different sources, which have looked into the discovery and use of lenses  in India, China and Europe have given convincing evidence that spectacles were invented around 1250-1300 in Italy allthough lens type structures were known of much earlier dates (Schlieman found them in Troje, they were found in Roman and Carthago remains in Norh Africa etc.). And it was a availability of a good supply of lenses and a clever mind that made Lipperheys invention possible.Interesting literature to read ( a whole libary full of fascinating studies exist).If you ever come to The Netherlands I can advise you to visit the magnificent Louwman museum of historical telescopes and binoculars in The Hague and you could spent an extra day in museum Boerhaave in Leiden (not far from The Hague) which also has a splendid collection of historical telescopes.Gijs</blockquote>

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