Four centuries since Galileo Galilei used a telescope for Astronomy…

But who invented the telescope?

Historical research has shown that Leonard Digges undoubtedly invented a reflecting telescope about a century before Isaac Newton did, and may also have made a refracting telescope.
However, the first patent-request for a telescope was made in 1608 by Dutch spectacle-maker Johannes Hans Lipperhey from Middelburg although two other spectacle-makers, Sacharias Jansen and Jacob Metius also claimed the invention.
Afterwards, the invention of the telescope was considered too easy to imitate to be awarded with a patent.

Philip Corneille
http://www.astronomy2009.org/
http://www.inventionofthetelescope.eu/

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This brings up a curious point - spectacles, not to mention things like glass beads, had been around for a long time, so why did it take so long for telescopes to appear? I find it hard to believe that either Galilean or Keplerian forms hadn't been hit upon numerous times before Lipperhey; it didn't take Galileo long to replicate and improve his products from, as far as I can tell, secondhand reports. This may be like the European discovery of North America - Columbus wasn't the first, but he was the one who made it back and told everybody, thereby adding it t the store of common knowledge in what became (eventually and slowly) a global community. I suppose individuals might have hit on telescopes at various earlier times but kept the details secret for a variety of reasons, or simply regarded them as curiosities. As I point out in classes, Galileo certainly didn't invent the telescope, and he may or may not have been the first to use one to look skyward. But he eas clearly the first to examine the skies systematically and make public what he found.

The above is an image of a putative Athenian telescope, on the cover of Robert Temple's book The Crystal Sun, which describes the existence of "hundreds" of ancient lens-like objects, some of which might have been suitable for astronomical use. I must confess that I am unconvinced, as we will likely never know for sure that these "lenses" were actually used in a working telescope (unless a complete telescope is unearthed in an archaeological dig somewhere). We simply do not know for certain today what any particular lens-like piece of glass, even it is of high optical quality, was used for. Some of the evidence I have read about does sound suggestive, but there are always alternative explanations other than astronomy.

Still, the possibility does exist that telescopes of some sort were being used, long before their official date of invention. But right now the conclusive evidence for this does not exist (in my non-expert opinion).

The chances of just anybody accidentally stumbling across the right arrangement of lenses for long-distance magnification isn't that high. First you need to have a lot of different lenses on hand; second, you need to be playing around with them in ways that are quite outside the normal range of activities for a 16th-century optician. If the general arrangement (two lenses, of two different kinds, held in line at some distance from each other) is known, then a little experimentation with different kinds of lenses could quickly yield the desired result. But if it's *not* known, under what circumstances would one accidentally discover it?

The earliest telescopes, IIRC, had a magnification of something like 3x (or less) and were little more than toys, though they still possessed enough utility to get people interested. Galileo had the scientific/engineering mindset that allowed him to devise experiments which would not only duplicate, but improve on the instrument. That mindset was very much a rarity at the beginning of the 17th century.