Astronomical instruments

Astronomy is an observational science which deals with stars, galaxies, clusters of galaxies and other heavenly objects. An astronomical instrument plays a major role in developing science in astronomy. Most commonly and extensively used instrument in astronomy is telescope. Three main varieties of telescope are optical telescope, radio telescope and Hubble space telescope. Telescopes which are used for observations in the optical wavelengths of the electromagnetic spectrum are known as optical telescopes. Here two types are there- refracting and reflecting. Refraction telescopes which are smaller in size are widely used. The important terms used in optical telescopes are magnifying power, image brightness, resolving power and focal ratio. Telescopes which are used for the detection of electromagnetic radiation emitted in the radio wavelengths are known as radio telescopes. Hubble space telescope is an orbiting telescope. Astronomical spectrograph is a widely used instrument which can separate a non-monochromatic light beam into its constituent wavelength followed by the recording of the intensities of the radiation according to the wavelengths. Here observations are made with naked eye with an eyepiece. The main part of a spectrograph is a dispersive medium which is either a prism made of glass/quartz or a diffraction grating. Modern photoelectric methods are employed in photoelectric photometry. The main parts of an astronomical photoelectric photometer are an eyepiece, a focal plane diaphragm, a field lens, filters and a detector with amplifier and a recording system. Stellar spectrophotometry, photographic spectrophotometry and photoelectric spectrophotometry are some other methods used in astronomy.