The invention of the refracting telescope and binocular

Telescopes of course need lenses.  Lenticular Bronze Age objects of  rock crystal have been excavated which from their shape were very probably used as magnifiers but unequivocal written record of such objects used as  optical aids appears to begin with Roger Bacon's Opus Majus (1268) in which he noted that a crystal or glass lens formed as a small portion of a sphere will magnify small objects beneath it when viewed from the convex side and that such an instrument is thus very useful for reading  by anyone with weak eyes .   In 1289 in a manuscript entitled Traite de con uite de la famille, di Popozo wrote: "I am so debilitated  by age that without the glasses known as spectacles, I would no longer be able to read or write. These have recently been invented for the benefit of poor old people whose sight has become weak".   It thus appears that the first spectacles were made between 1268 and 1289, though it is very possible that monocles or "perspective glasses" were made before that time.
 To correct di Popozo's presbyopia converging (convex ) lenses would be used.  It was nearly two hundred years after his time before diverging (concave) lenses began to be used to correct  myopia (short-sightedness).   Nicholas of Cusa is widely accredited with this innovation, in 1451, but on very slender grounds.   It is certain that by 1466 spectacles giving "distant vision for the young" were being made in quantity in Florence but, as with spectacles using convex lenses, we do not know who designed or made the first pair.    

In a flight of fancy, Roger Bacon had predicted that by refraction distant things would be made to appear near, but 340 years were to pass before the telescope was invented.   When they eventually appeared, the telescope and (compound) microscope were invented within twenty years of one another, both in the Dutch town of Middelburg .  We intend to discuss the invention of the microscope in a separate post.   As far as that of the telescope is concerned, we note that in early October, 1608, Hans Lippershey of Middelburg in Zeeland, with a view of obtaining a patent, submitted for inspection of the States General in the Hague details of a small telescope consisting of a tube with a convex lens at one end and a concave at the other, magnifying three times.  Three weeks later, a submission was made by Jacob Metius, of Alkmaar, a hundred miles or so to the north of Middelburg, that he could make a telescope quite equal to Lippershey's and of cheaper materials.  Neither patent was granted, on the grounds that the ideas had already become known, but Lippershey was asked by the States General if he could make a device though which one could look with both eyes.  He obliged with the first binocular, and made several, for which he was well paid.  Interest in binoculars soon waned, probably because of the difficulty in making two identical telescopes and holding them in exact alignment. 
 It is perhaps surprising  lenses had been used singly for several centuries before they were combined to form the compound microscope and the telescope. Two possible reasons for this are first, the lack of technical means to make lenses of  high sufficiently high quality and second, the lack of a useful theory  of light - as it was, progress appears to have been made largely by trial and error.
Be that as it may,  once the cat was out of the bag, detailed news of the invention of the telescope spread rapidly throughout Europe and Thomas Harriot made observations of the moon in August 1609 and of sunspots in December of that year, while in January 1610 Galileo viewed the four largest moons of Jupiter.