In 1608, a Dutch eyeglass maker named Hans Lippershey looked at a church steeple through two lenses placed one in front of the other and saw that the image was magnified. Unfortunately the telescopes built on Lippershey's model had poor image quality, caused by the bending of light though the glass lenses. (Glass does not bend the different colors of light equally. Red light is bent the least causing a colour distortion in the image.) Isaac Newton eventually solved this problem in 1668 by making a telescope that worked with mirrors instead of lenses.

Galileo Galilei Was the first person to use the telescope to seriously study the heavens. Galileo was able to see that the moon was not smooth, but covered with huge valleys and craters. He discovered four moons orbiting Jupiter and found out that Venus has phases just like the moon. He realized that this must mean that Venus, and the other planets, revolve around the sun not around the earth, as many people believed at the time. In 1610 Galileo published a book about what he had seen through his telescope. Starry Messenger became the seventeenth-century equivalent of a bestseller. Not bad!

Galileo( Italy,1564-1642). was given credit for the discovery of the telescope because he was the first to publish his findings in March of 1610. Though Galileo did not invent the telescope and probably was not the first individual to look at the sky with one of the first, crude refracting systems, his improvements to the quality of the lenses used and the discoveries resulting from his application of the instrument to the celestial sphere triggered an observational revolution in astronomy that continues even today, as astronomers attempt to squeeze more photons, more information, and more insight from objects at greater and greater distances.

By Isaac Newton ( England, 1642-1727)'s time, it was also well known that water droplets would produce a rainbow by the same prism effect of each droplet. The problem with refracting telescopes was that the lens acted like a prism, breaking up white light into its constituent colors. It then focuses each color on slightly different point. A bright star or planet viewed through a telescope would have a noticable red and violet halo around it. Color aberration in an objective lens reduces the contrast of the images and covers up small details. Newton suggested a completely different approach: do away with the lenses altogether and use a curved mirror to reflect and focus the white light (and all of its colors) to a single point. A mirror does not "refract", or bend the light and create a rainbow. Newton placed a second, flat, smaller mirror in front of the curved mirror to catch the rays of light and reflect them out the side of the tube to an eyepiece, which would magnify the image. the first reflecting telescope,1.5" speculum metal, was made by Newton in 1672.
An 18th-century brass reflecting telescope with a 4.5 inch mirror (112 mm). 26-inch (66cm) long tube covered with ray skin. The screw rod moves the mirror to focus. Small star-finder scope attached. Mounted on a simple, alt-azimuth mount. The altitude and azimuth are adjusted by two turn keys which turn a screw drive. Pillar and stand with cabriole legs and inswept feet, in original plush lined mahogany case.

Early 19th-century lacquered brass refractor. 3 inchs objective lens. 35 inchs long tube with rack and pinion focusing. Lens cap, small slide to protect eyepiece. Five additional eyepieces.

19th-century brass reflecting telescope with 2.5 inchs primary mirror. The scope is small, having a body tube only 11 inches long.
The first pair of modern prism binoculars were adapted from a telescope invented by an Italian citizen named Ignatio Porro(Italy,1801-1875) in 1854. Ignatio Porro designed a telescope using two prisms set at right angles to each other between the objective lens and the eyepiece. 

Porro prism vs. roof prism Porro prism binoculars were standard until the 1960's, when the Zeiss and Leitz companies introduced roof prism binoculars, whose objective lenses were straight in line with the eyepieces. Roof prism binoculars were compact, light, and comfortable to hold. They made the offset, zig-zag shape of the Porro prism design look as old fashioned as propeller-driven aircraft.

Through the 20th-century, all kinds of telescope were developed, the function of telescope was expanded widely, such as modern telescope, astronomical telescope, rifle scopes, night vision goggles etc.

 

In 1962, the USA's National Academy of Sciences recommends building a large space telescope. In 1977, Congress votes to fund the project and construction of Hubble Space Telescope begins. Construction of Hubble Space Telescope was completed in 1985. The launch of Hubble was delayed due to the 1986 Space Shuttle Challenger disaster. Hubble was launched on the space shuttle on April 25, 1990.