Telescopes are being used by astronomers to watch objects that seem too faint when directly approached by our eyes. The primary aim of the telescope is to seizure extra light more than an eye is capable to catch and to emphasize that light on eye, part of film or any electrical sensor to generate an image. Many great images of the universe have been produces by telescopes.  A simple telescope was first invented by an Italian creator Galileo in the 1600s, but as the astronomy got popular, the improvement in telescopes have yet not been made till 1900s. The telescopes got advanced and much bigger by the 20th century; it enabled the astronomers to identify the far objects in space.
Home astronomy gain popularity in 20th century, the advancement in home telescopes is good enough to study stars, planets and galaxies that remained unfamiliar to experts like Galileo. The initially known operative telescopes did appear in 1608 and are the efforts of Han Lippershey. In 1611, Johannes Kepler did explain the formation of telescopes with the help of conves objective and convex eyepience lens. In 1655 Christiaan Huygenswere did build powered but clumsy telescope with joined eyepieces. Isaac Newton is honored as the creator of the first real-world reflector in 1668. In 1672 Laurent Cassegrain explained the structure of a reflector having a little convex glass for reflecting the light within a center hole in the primary glass. 
There are some of the currently used Telescopes such as Large Binocular Telescope and Gran Telescopio Canarias. Large Binocular Telescope (LBT) An optical Telescope as Large Binocular Telescope (LBT) is used in astronomy and is positioned at Mount Graham in the pinaleno Mountains of southeastern Arizona and is fragment of the International observatory of Mount Graham. LBT stands as the one of the most advanced telescope of world, having two 8.4m broad glasses that give the similar light focusing capability as 11.8m broad singular round telescope.
Any one of its mirror could be the biggest optical telescope in North America. The ratios as for 95 % Strehl in M band and 60-90 % in H band are attainted by the LBT. The total cost for a telescope was calculated as from $970 million to $1.2 billion. The funds have not been gathered completely by the mid of 2011; however $100 million have been spent on designing, manufacturing and site-observation work. 
Figure 2: Large Binocular Telescopes Gran Telescopio Canarias (GTC): The other Telescope Gran Telescopio Canarias (GTC) having glasses of a diameter of 10.4-meter crows more light-combining area than any other tool of this type. Its inauguration is planned in Canary Islands of Spain. From the University of Florida, the astronomers and officers with more than 500 astronomers will join to make the project successful. There are some advanced next generations advanced telescopes such as TMT and E-ELT. There specifications are little explained with the comparison to both generations.
Figure 3:Gran Telescopio Canarias Thirty Meter Telescope (TMT): Thirty Meter Telescope (TMT) is considered as it will be the world’s tops advanced and proficient ground-focused mid-infrared, near-infrared and optical telescope. It will join the advance inventions of accuracy control, sectioned glass design and adaptive optics. The TMT will have the ability of being the most advanced and skilled telescope. It will possess the capability to read the objects which are not very visible or are very far and to focus them with the current services and will be a main toll for answer most of the convincing and vital queries in existing science. 
Figure 4: Thirty Meter Telescope Extremely Large telescopes: Extremely Large telescopes are thought to be the one of the biggest significances in ground-functioned astronomy. It will greatly elaborate astrophysical information, permitting the in detail study of subjects containing planets of other stars, the initial objects of the complete universe, huge holes of black color, and the circulation and nature of the murky matter and energy that have dominance over the universe.  Here comes some difference with two generations i.e. of current and next generation.
The biggest ground-mounted telescope functioning currently is Gran Telescopio Canarias having an aperture of 10.4 m and light-combining zone of 74m2. There are some other scheduled tremendously big telescopes that contain 30 m/655 m2 Thirty Meter Telescope and 25 m/368 m2 Giant Magellan Telescope which are also a target at the ending of this era or the staring of next decade for accomplishment. The above described telescopes relate to the next generations of optically ground-mounted telescopes.
The design of these is much broader than the early ones. The telescope is considerably greater than the other deliberate telescopes, even with the scrape of the E-ELT, having a diameter of 39.3m for the main glass and 1116 m2 of light-combining surface. The next generation telescopes will possess various scientific instruments. It will also be likely to shift from one tool to another within some minutes. The vault and telescope will be capable to alter locations on the sky and to begin a new reflection within a small duration. The next generation telescopes will not also add the detection of planets downcast to Earth, like objects through unintended calculations of the shaking movement of the stars disturbed by the planets that path them, but also having the straight photography of greater planets and likely the description of the environment.
Moreover, the next generation set of tools will permit the astronomers to investigate the initial steps of the creation of the terrestrial system and to perceive water and biological particles in proto terrestrial plates about stars in the forming. The telescopes will response the basic queries related to the planet creation and development. By searching the very far entities the E-ELT will give signs to considerate the creation of the starting entities that made, primeval stars, primeval galaxies and dark dumps and the associations between them. Studying large entities as dark holes will facilitates from the control of the E-ELT to attain more vision to time-forming spectacles joined with the different methods at production about dense entities.
The next generation telescopes are designed to form the complete description of the principal galaxies and to track their development through galactic era. Studies of the initial galaxies with the advanced telescopes like E-ELT will provide signs that will assist in understanding the formation and evolvement of the objects . Moreover, the next-generation telescope will be a different apparatus for forming a catalog of the altering values of the different entities in universe during time and to realize star creation background of galaxies.