-By Rishi Shah & Sudeep Neupane
A telescope is a unique astronomical instrument that has been invented cleverly to observe and study remote objects. Its invention was subjected to sequence of events that cannot be assigned to an exact time or place. There are several written references to telescopic gadgets in ancient times, but no solid evidence as to their construction and use could be determined and verified. After the Phoenicians with enterprising maritime trading culture that spread across the Mediterranean had discovered glass around 3500 BC, while cooking on sand, it took about five thousand years for glass to be shaped into lens for the telescope. Historically since avid spectacle (eyeglass) maker Hans Lippershey (1570-1619) had probably assembled the first practically functioning telescope, he is often credited with its invention. He had allegedly applied for patent for exclusive manufacturing of telescopes in 1608, but was denied, based on the argument that the devices were already known to other parties. However, Lippershey was hired as telescope maker to the State of Zeeland which is now a province in Holland.
The telescope was introduced to astronomy in 1609 by the great Italian astronomer Galileo Galilei (1564-1642). He became the first man to peer at the stars, phases of planet Venus and moon’s craters and watched four awesomely fascinating large moons of Jupiter along with arcane rings of Saturn. He revealed the sunspots and many other breath-taking entities of our universe. Galileo’s telescope was similar to a pair of opera glasses which applied an arrangement of glass lenses to magnify objects. It provided limited magnification of up to thirty times within uneasily narrow field of view. Galileo’s support for Copernicus’ heliocentric postulation prompted serious conflict with Catholic Church and caused him troubles. In 1704, the famous British genius astronomer Sir Issac Newton (1643-1727) improved the design and utilized telescopes intensively for astronomical purposes. He introduced innovative concept in telescope design whereby instead of glass lenses, a curved mirror was exploited to gather light and reflect it back to a point of focus. This reflecting mirror acted like a light-collecting bucket (bigger the bucket, the more light could be accumulated). The reflector telescope opened the door for magnifying heavenly images millions of times. He produced the first reflecting telescope which is dubbed as Newtonian reflector. Telescope making has evolved as an extraordinary discipline ever since.
The application of achromatic lens in 1733 partially corrected color aberrations (focusing failure) present in the simple lens and enabled the construction of shorter and more functional refracting telescopes. In reflecting telescopes, though not limited by the color problems as seen in refractors, the mirrors were improved by silver or aluminum coating. Refractor telescope can possess huge sizes like the one at Yerkes Observatory, Wisconsin, USA (circa 102 centimeter lens diameter with 19.4 meters focal length). The biggest reflecting telescopes currently boast of objectives surpassing ten meters like the modern Gran Telescopio Canaris (10.4 meters) in Canary Islands, Spain and the Large Binocular Telescope (11.7 meters) in Arizona, USA. In catadioptric telescopes mirrors are combined with lenses to form captivating images.
Telescopes can be classified under distinct categories with respect to their operation in peculiar electromagnetic radiation. Optical and radio telescopes are extensively used in astronomy. High energy particle telescopes and gravitational wave telescopes carry out specialized observational assignments. Except terrestrial telescopes operating in broad wavelength range, National Aeronautics and. Space Administration (NASA), Russian Federal Space Agency (RKA), European Space Agency (ESA), Canadian Space Agency (CSA) have been exploring universe through different types of space telescopes. Compton Gamma Ray (already decommissioned) and Chandra X-Ray telescope, Spitzer Space Telescope and Hubble Space Telescope (HST) are NASA’s vital missions in the history of space telescope. HST is marvelously versatile iconic and comparatively expensive space telescope which has been divulging secrets and mysteries of universe since 1990. James Webb Space Telescope (JWST) is being designated as the successor to HST. JWST would scrutinize space in infrared spectrum. ESA has also ambitiously lifted-off Hershel Space Observatory and Planck Telescope into space.
Besides the sophisticated telescopes for astronomers, homemade telescopes have contributed substantially for the betterment of astronomy activities. The advent of amateurs in building telescopes for their own enjoyment and education has come into prominence in the 20th century. The types of telescopes that they build vary widely from very modest to beguiling ones including refractors, Schmidt Cassegrains and Maksutovs.
The most important components of telescope are the optics, primary and secondary mirrors. When building a telescope its mirror has to be painstakingly ground and polished to an extremely accurate shape (usually paraboloid) although telescopes with high focal ratios could adhere to spherical mirrors.
Telescopes can offer the perplex beauty and fascination of our cosmos. They could couple us together with those queer celestial bodies that are lying eons of light-years away and connect us to their mind-boggling movements. Telescope making could emphatically stress the significance in creating awareness in astronomy in our society. Additionally telescopes help us to satisfy our personal interest for logical information on baffling phenomena and conundrums that are related to our evolution of life on earth. Since people around the globe are celebrating the International Year of Astronomy 2009 with the slogan the universe is yours to discover, we too could attempt to comprehend our puzzling universe and our Solar System through our own handmade telescopes.
Source:The Rising Nepal,National English Daily,Monday,24th August,2009