He concluded that light could not be refracted through a lens without causing chromatic aberrations, although he incorrectly concluded from some rough experiments that all refracting substances would diverge the prismatic colors in a constant proportion to their mean refraction. From these experiments Newton concluded that no improvement could be made in the refracting telescope.
With one of these: an objective diameter of 2.24 inches (57 mm) and a 12 ft (3.7 m) focal length, he discovered the brightest of Saturn's satellites (Titan) in 1655; in 1659, he published his "Systema Saturnium" which, for the first time, gave a true explanation of Saturn's ring—founded on observations made with the same instrument.
decades after Galileo’s death, Isaac Newton published his Laws of Motion and Universal Law of Gravitation, which heavily leaned on the findings of Galileo
Galileo Galilei was recently selected as a main motif for a high value collectors' coin: the €25 International Year of Astronomy commemorative coin, minted in 2009. This unique addition allowed the image to be viewed with minimal obstruction of the objective mirror. , Johannes Kepler first explained the theory and some of the practical advantages of a telescope constructed of two convex lenses in his Catoptrics (1611). Objects resembling lenses date back 4000 years although it is unknown if they were used for their optical properties or just as decoration.
He went completely blind in 1638 and was suffering from a painful hernia and insomnia, so he was permitted to travel to Florence for medical advice. Objects resembling lenses date back 4000 years although it is unknown if they were used for their optical properties or just as decoration. Using this telescope, he made his early brilliant astronomical discoveries. , Because of their illegitimate birth, their father considered the girls unmarriageable, if not posing problems of prohibitively expensive support or dowries, which would have been similar to Galileo's previous extensive financial problems with two of his sisters. The design he came up with bears his name: the "Gregorian telescope"; but according to his own confession, Gregory had no practical skill and he could find no optician capable of realizing his ideas and after some fruitless attempts, was obliged to abandon all hope of bringing his telescope into practical use. The same techniques have now been applied at a number of other astronomical telescope arrays including: the Navy Prototype Optical Interferometer, the CHARA array, and the IOTA array. , William Gascoigne was the first who commanded a chief advantage of the form of telescope suggested by Kepler: that a small material object could be placed at the common focal plane of the objective and the eyepiece. Adopting a hypothetical law of the dispersion of differently colored rays of light, he proved analytically the possibility of constructing an achromatic objective composed of lenses of glass and water. Earlier, Pope Urban VIII had personally asked Galileo to give arguments for and against heliocentrism in the book, and to be careful not to advocate heliocentrism.  In fact, there is little doubt that both of them were beaten by David Fabricius and his son Johannes. At the start of 1616, Monsignor Francesco Ingoli initiated a debate with Galileo, sending him an essay disputing the Copernican system. telescope design.