Astronomical telescopes

Telescope is an essential tool in astronomy. An astrologist relies mainly on telescopes for astronomical observations. An optical telescope helps to observe optical wavelengths of the electromagnetic spectrum. There are two types of optical telescopes – refracting and reflecting. Here a real image of an object is formed at the focus of the larger lens/mirror. This image, with the help of an eyepiece is magnified. Refracting type telescope is smaller compared to reflecting type and hence it is commonly used and preferred. Magnifying power of a telescope is the ratio of the focal length of the objective lens to the focal length of the eyepiece. Image brightness depends on the objective aperture. The light gathering power of a lens or mirror is proportional to the square of its aperture. Telescopes which are used to detect electromagnetic radiation emitted in the radio wavelengths are known as radio telescopes. Here radio waves from cosmic sources are reflected from a paraboloidal dish to a dipole antenna. A receiver is used for energy transmission and an amplifier for amplification. Hubble space telescope is an orbiting telescope located in space which gives sharper images than other ground based telescopes.