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Telescope History
Shortly following the release of Galileo's original telescope model, critics and academic minds across the European continent attempted to provide innovative solutions for correcting the telescope's color aberration design flaw. In 1613, a French philosopher named Descartes wrote to Galileo, suggesting for replacement of the telescope's simple lens in favor of hyperbolic lenses. In 1632, one of Galileo's pupils, and the University of Bologna's professor of mathematics, Bonaventura Cavalieri published Specchio ustorio. Within the work, Cavalieri proclaimed his desire for constructing a reflecting telescope for testing the possibility of igniting a fleet of wooden ships using only a telescope. Following his fantasy proclamation, Cavalieri discussed the data he obtained through his observation of beams of white light reflecting off of glass prisms. Cavalieri found that according to the law of reflection, a beam of light directed upon the conical section of a prism, the reflected beam will radiate from the opposite end in a pattern reminiscent of Euclidian geometry. Cavalieri constructed three different illustrated concepts for incorporating reflective mirrors within his telescope model. Plan one consisted of a large, concave mirror directed towards the sun as to reflect light into a second, smaller, convex mirror. Cavalieri's second concept comprized of a main, truncated, paraboloid mirror and a second, convex mirror. His third option illustrated a strong resemblance to his previous concept, replacing the convex secondary lens with a concave lens.

In 1663, James Gregory had constructed his design for a reflecting telescope, which incorporated two large, parabolic, primary mirrors along with one large, elliptical mirror, located just past the focal point of the two primary mirrors, within the telescope. Following the completion of his sketch, Gregory commissioned London optician, Richard Reeves to construct the telescope's mirror, only for Reeves to accidentally damage the mirror through improper polishing methods and rendering it unusable. As a consequence of Reeves' mistake, Gregory was unable to construct a physical model, eventually resulting in him forcefully abandoning the project. Shortly proceeding the cancellation of Gregory's telescope, Sir Issac Newton continued to abject heavy criticism in regards to Reeves' polishing methods, believing that he should have used quick-silvered glass as opposed to speculum metal.

In 1666, Sir Issac Newton had noted that the effect of chromatic aberration was the result of light creating optical refraction as it passed through a lens. Newton had taken advantage of the time he granted following a severe bubonic plague outbreak at Cambridge, to begin creating sketches for his modified telescope design. The design of Newton's telescope incorporated one large, concave spectrum mirror positioned at the along with a secondary mirror angled at a 45° angle, which allowed for the image to reflect into the eye lens at a 90° angle.

While the exact appearance of Newton's first telescope remains a mystery, autograph illustrations preserved at the Cambridge University Library suggested that the telescope had measured around 8-9 inches long and possessed a crude, unstable mount. Newton tested his first telescope by observing Jupiter, and with its four Galilean satellites, along with recording Venus and its many phases. Information involving Newton's first telescope remained restricted among only his close friends, with the telescope achieving recognition following the development of Newton's second telescope. Newton's second telescope had a measured focal length of ~6.25-6.33 in and incorporated a wooden ball within the mount, which allowed nearly 360° rotation at a fixed joint. This new telescope also possessed a thicker, clearer, 2 in diameter spectrum, which improved viewing image quality. Newton heavily favored his second telescope over the original, as he seldom preserved articles detailing his first telescope. Following the creation of the second telescope, Sir Issac Newton received an invitation from the newly founded Royal Society in London for evaluation. Newton's telescope managed to highly impress the Royal Society's council members, resulting in Newton's election as an official member of the Society.

In 1672, a Frenchman named Cassegrain (no records of first name present) constructed a third, unique reflecting telescope design. Cassegrain's design incorporated a single, concave primary mirror, in a similar vein to the Newtonian model, but also included a convex secondary mirror. Despite information regarding Classical Cassegrain reflecting telescope usage and its creator remaining unknown, Cassegrain sketch models saw increased modification by fellow scientists, such as astronomers George Willis Ritchey and Henri Chrétien in 1910, as the field of astronomy continues to advance.