However, Galileo perfected the refracting telescope within a year and he became the first one to point a telescope up to the sky for observation.
Refracting telescope: Refraction refers to the bending of light when it passes from one medium to another of different density. These telescope use a large lens called an objective lens. The main purpose of the lens is to collect light as possible. The lens has a convex (curved outward) shape making it thicker in the middle than the edges. This thickness slows the light waves as they pass through the glass, bringing the waves into focus at the same time.
Reflecting telescopes: Reflection refers to the use of a primary mirror to reflect the light back to a focus instead of refracting it. These telescopes use a concave (curved similar to a bowl) mirror instead of a lens. This mirror is called a primary mirror. The mirror is concave so that any line across the center of the mirror is a parabola. A parabola is an open curve formed by an object traveling a path. If a mirror has this shape, it is called a parabolic mirror, which reflects light rays to a sharp focus in front of itself. Then a second mirror reflects the rays to an eyepiece.
Refracting and reflecting telescopes are both used to examine the visible light region of the electromagnetic spectrum. However, the reflecting telescope also examines the shorter and longer wavelengths near it. These wavelengths are the ultraviolet and infrared.
There are five main problems with the refracting telescope:.
Spherical Aberration: the spherical surfaces of objective lenses don't bring all light into focus at the same focal length, causing a distorted image.
Chromatic Aberration: since different colors of light have different focal lengths, they can't be brought into focus properly, which causes a distorted image.
Sagging of the Objective Lens: the lens is so thick in the center and thin on the edges, that it can't be supported properly and becomes deformed causing light to come into focus at different focal lengths.
