Galileo knowledge of optics and the functioning of the telescope revised

TL;DR

This paper investigates Galileo's understanding of optics and his telescope's functioning by analyzing extant instruments and replicas, revealing his advanced optical knowledge and practices in early telescope use.

Contribution

It provides a new interpretation of Galileo's optical knowledge based on physical analysis of his telescopes and their use, challenging previous assumptions.

Findings

Galileo's telescopes were designed with advanced optical understanding.

Galileo addressed key optical issues like illumination and resolution.

His optical knowledge was rooted in a novel optical framework.

Abstract

What are the historical evidence concerning the turning of the spyglass into an astronomical instrument, the telescope? In Sidereus Nuncius and in his private correspondence Galileo tells the reader what he did with the telescope, but he did not disclose the existence of a theory of the instrument. Still, the instruments which Galileo produced are extant and can be studied. With replicas of Galileo's telescopes that magnify 14 and 21 times, we have simulated and analyzed Galileos practices as he reported them in Sidereus Nuncius. On this ground, we propose a new solution to this old problem. We establish the knowledge of optics that Galileo had as it can be read off from the telescopes he constructed and the way he put them to use. Galileo addressed optical difficulties associated with illumination, resolution, field of view, and magnification. His optical knowledge was well thought through, originated as it did in a radically new optical framework.