Optical telescope
The telescope is more a discovery of optical craftsmen than an invention of a scientist. The lens and the properties of refracting and reflecting light had been known since antiquity and theory on how they worked were developed by ancient Greek philosophers, preserved and expanded on in the medieval Islamic world, and had reached a significantly advanced state by the time of the telescope's invention in early modern Europe. But the most significant step cited in the invention of the telescope was the development of lens manufacture for spectacles, first in Venice and Florence in the thirteenth century, and later in the spectacle making centers in both the Netherlands and Germany. It is in the Netherlands in 1608 where the first recorded optical telescopes (refracting telescopes) appeared. The invention is credited to the spectacle makers Hans Lippershey and Zacharias Janssen in Middelburg, and the instrument-maker and optician Jacob Metius of Alkmaar.
Leonard Digges (scientist)
The writings left by Digges' colleague William Bourne contain further detail on the experiments with lenses and mirrors conducted by Leonard Digges and his son. It is these details which led some researchers, most notably Colin Ronan, to claim that Leonard Digges invented a functioning telescope sometime between 1540 and 1559. The description seemed to suggest that Digges created a rudimentary instrument incorporating lenses and a concave mirror, in a manner rather different from a modern reflecting telescope. However, the construction of lenses to the required optical precision would have been very difficult in the 16th century, and the construction of an adequate mirror would have been much harder still. It is doubtful that Digges built a successful instrument, and the optical performance required to see the details of coins lying about in fields, or private activities seven miles away was far beyond the technology of the time.