One day in the early 17th century, Hans Lippershey, the owner of an optical shop in a small Dutch town, arranged a convex lens and a concave lens in a line to check the quality of the polished lens. Looking through the lens, he found that the church spire in the distance seemed to be getting bigger and closer, so he accidentally discovered the secret of the telescope. In 168, he applied for a patent for his telescope, and in compliance with the requirements of the authorities, he built a binocular. It is said that dozens of opticians in the town claimed to have invented the telescope, but it is generally believed that Lieberthe was the inventor of the telescope.
The news of the invention of the telescope quickly spread in European countries. After learning the news, Italian scientist Galileo made one himself. The first telescope can only magnify the object three times. A month later, the second telescope he made can be magnified 8 times, and the third telescope can be magnified 2 times. In October 169, he made a telescope with a magnification of 3 times. Galileo observed the night sky with a homemade telescope and found for the first time that the surface of the moon was uneven, covered with mountains and cracked with craters. Since then, four moons of Jupiter and the sunspot movement of the sun have been discovered, and the conclusion that the sun is rotating has been made. Almost at the same time, Kepler, a German astronomer, began to study telescopes. He proposed another kind of astronomical telescope in Flexion Optics, which is composed of two convex lenses. Unlike Galileo's telescope, it has a wider field of vision than galileo telescope. But Kepler didn't make the telescope he introduced. Sajna made this kind of telescope for the first time between 1613 and 1617. He also made a telescope with a third convex lens according to Kepler's suggestion, and turned the inverted image of the telescope made of two convex lenses into a positive image. Sajna made eight telescopes, one for observing the sun, and no matter which one can see sunspots with the same shape. Therefore, he dispelled the illusion that many people think that sunspots may be caused by dust on the lens, and proved that sunspots are indeed observed real existence. When observing the sun, Sajna installed special shading glass, but Galileo didn't add this protective device. As a result, he hurt his eyes and finally became almost blind. Huygens of the Netherlands made a telescope with a tube length of nearly 6 meters in 1665 to explore Saturn's rings, and later made a telescope with a tube length of nearly 41 meters.
A telescope using a lens crop mirror is called a refracting telescope. Even if the lens barrel is lengthened and the lens is machined accurately, the chromatic aberration cannot be eliminated. Newton once thought that the chromatic aberration of a refracting telescope was hopeless, but it turned out to be too pessimistic. In 1668, he invented the reflective telescope, which solved the problem of chromatic aberration. The first anti-telescope is very small, and the aperture of the mirror in the telescope is only 2.5 cm, but the satellite of Jupiter and the profit and loss of Venus can be clearly seen (see attached figure 1). In 1672, Newton made a bigger reflecting telescope and gave it to the Royal Society, which still exists in the library of the Royal Society. In 1733, Hal, an Englishman, made the first achromatic refraction telescope. In 1758, Boland of London also made the same telescope. He used glasses with different refractive indexes to make convex lenses and concave lenses respectively, so as to cancel out the colored edges formed by them. However, it is not easy to make a large lens. At present, the largest refractive telescope in the world has a diameter of 12 cm and is installed at the Yadis Observatory. In 1793, William Herschel, England, made a reflective telescope. The diameter of the mirror was 13 cm, made of copper-tin alloy and weighed 1 ton. In 1845, reflecting telescope made by William Parsons in England had a mirror with a diameter of 1.82 meters. In 1917, the Hooker Telescope was built at Mount Wilson Observatory in California, USA. Its primary mirror has a diameter of 1 inches. It was with this telescope that Edwin Hubble discovered the amazing fact that the universe is expanding. In 193, German Bernhard Schmidt combined the advantages of refractive telescope and reflecting telescope (refractive telescope has small aberration but chromatic aberration, and the larger the size, the more expensive it is; reflecting telescope has no chromatic aberration, and the cost is low, and the reflector can be made large, but there is aberration), and made the first folding reflecting telescope.
After the war, the reflective telescope developed rapidly in astronomical observation. In 195, a 5.8-meter-diameter Hale reflective telescope was installed on Paloma Mountain. In 1969, a reflector with a diameter of 6 meters was installed on the Pastukhov Mountain in the northern Caucasus of the former Soviet Union. In 199, NASA put the Hubble Space Telescope into orbit. However, due to mirror failure, it was not until 1993 that astronauts completed space repair and replaced the lens that the Hubble Space Telescope began to fully play its role. Because it can be free from the interference of the earth's atmosphere, the image definition of Hubble telescope is 1 times that of similar telescopes on earth. In 1993, the United States built a 1-meter-diameter Keck Telescope on Mount Monaque, Hawaii. Its mirror was made up of 36 1.8-meter mirrors. In 21, the European Southern Observatory in Chile developed the "VLT", which consists of four 8-meter-diameter telescopes, and its focusing capacity is equivalent to that of a 16-meter reflecting telescope. Now, a number of telescopes under construction have begun to attack the white giant brothers on Mount Ashan in Monaque. These new competitors include the 3-meter caliber California Extremely Large Telescope (CELT), the 2-meter caliber Giant Magellan Telescope (GMT) and the 1-meter caliber Overwhelming Large Telescope (OWL). Their proponents point out that these new telescopes can not only provide space pictures with far better image quality than those of Hubble telescope, but also collect more light, learn more about the initial stars and cosmic gases when galaxies formed 1 billion years ago, and see clearly the planets around distant stars.