Refracting telescope focus, results in a non-inverted and upright image. Galileo’s best telescope magnified objects about 30 times. Because of flaws in its design, such as the shape of the lens and the narrow field of view, the images were blurry and distorted. Despite these flaws, the telescope was still good enough for Galileo to explore the sky. The Galilean telescope could view the phases of Venus, and was able to see craters on the Moon and four moons orbiting Jupiter. Parallel rays of light from a distant object (y) would be brought to a focus in the focal plane of the
History of the telescope the Galilean telescope for these early forms of telescope that employed a negative lens. Johannes Kepler first explained the theory and some of the practical advantages of a telescope constructed of two convex lenses in his "Catoptrics" (1611). The first person who actually constructed a telescope of this form was the Jesuit Christoph Scheiner who gives a description of it in his "Rosa Ursina" (1630). 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