Telescopes are most often used for astronomical observation. Findings from his star watching convinced Galileo Galilei of the Copernican theory. In Japan, Tokugawa Yoshimune, the eighth shogun of the Edo shogunate of Japan, is said to have enjoyed star watching. Since the ancient times, telescopes have also been used for communication. They have recently found use in laser-based optical communication with artificial satellites. The close integration of lenses, mirrors, mount, dome, and control software ensures high observation accuracy. Japan-based Nishimura Co., Ltd. installed a telescope in an observatory that is located higher than any other observatory in the world. Another Japanese company, an electrical appliance manufacturer, built the world’s largest telescope. Japanese technologies are opening up a bright future for telescopes.
Premodern Uses of Telescopes: Star Watching and Communication
Throughout history, telescopes have been used for two purposes: star watching and communication. In 1608, a Dutch optician named Hans Lippershey found that looking at distant objects through two lenses makes them appear closer. In the following year (1609) , Galileo Galilei invented a three-power telescope, directing its outer end to outer space. Called the Galilean telescope, the primitive refractor employed in those days had a convex lens as the objective lens and a concave lens as the ocular or the eye piece. The Italian astronomer used such a telescope to observe craters on the moon. Studying how Saturn had rings and how Jupiter’s four satellites moved around the planet, he thought that the solar system was governed by the same principles as those smaller systems, which triggered his conversion from the Ptolemaic geocentric theory to the Copernican model. Scientists say that these observations through initial telescopes led Galilei to advocate heliocentrism. Japanese tradition has it that Kunitomo Ikkansai, a famous gun manufacturer in the late Edo period, embarked on building a telescope in 1792, later completing a reflecting telescope of the Gregorian type, featuring a concave primary mirror and an ellipsoidal concave secondary mirror. Tokugawa Yoshimune (1684–1751) , the eighth shogun of the Edo shogunate, is said to have built an observatory in the Edo Castle and observed objects in person day and night. Some of the “Yoshimune telescopes” believed to have been used on those occasions have been passed down until today.
Telescopes’ benefit of making distant objects look closer has also been used for communication purposes. Here, beacons were in use from ancient times until the relatively recent past. This method of setting up a fire at a prominent position so as to be seen from distant locations was used in the military, for example as a warning of an enemy attack. It can transfer information faster and over a longer distance than physical transport by humans or horses. However, it is easily affected by weather and can only convey a small amount of information corresponding to whether or not smoke is emitted. Toward the end of the 18th century, Europe saw the invention of the semaphore line, a communication system that used signaling mechanisms showing character codes, which were read from distant locations—using telescopes. “Hatafuri” or flag waving, a communication system featuring the use of telescopes, was used in Japan from the Edo period to early in the Taisho period (1912–26) .
Starting with Foreign-Made Products, Japan Has Developed the Ability to Make High-Precision Telescopes
Japanese telescope making, which has made big strides since World War II, laid its groundwork before and during the war. In the Meiji period (1868–1912) , the majority of telescopes and binoculars used in this country came from Germany. The military employed foreign-made products during the Russo-Japanese War (1904–05) . According to historians, the binocular used by Admiral Heihachiro Togo (1848–1934) during the war was made by Carl Zeiss AG. Fujii Lens Seizo-sho (Fujii Optical Works, currently Nikon Corporation) was the first binocular manufacturer in Japan, producing and distributing its first model in 1911, which was adopted by the Imperial Navy.
In 1926, Nishimura Co., Ltd. built the first Japanese reflecting telescope and delivered it to Kyoto University. In 1929 the company made and delivered the first Japanese 15-cm refracting telescope. These milestones were followed in 1932 by the building of a telescope for detecting the Einstein effect, which was also delivered to Kyoto University. Nishimura continued to refine its technology by making deliveries to the Tokyo Astronomical Observatory (currently the National Astronomical Observatory of Japan) and manufacturing reflecting telecamera before the end of World War II.
Customer needs to see darker stars are more difficult to fulfill in telescope making. Making dark stars visible requires extending the lens and/or mirror diameters to pick up more light. Resolution is another requirement. Suppose you try to find a planet going around a star through an astronomical telescope. Higher resolution means that your telescope can show the two objects not as being bonded together, but as being separate. This requires not only high accuracy from the lens and/or mirror, but also a measuring technique to see if they have ideal spherical and aspherical surfaces. Also indispensable is a technology for putting together such high-precision components. The slightest error in assembly would be a fatal mistake.
Telescope structure remains much the same since the first telescope was invented. Accuracy has been improved dramatically, however. And that is exactly where Nishimura is strongest. As President Nishimura puts it: “Before the war, our previous President could put together telescopes to such precision as to be considered irreproducible forever.” Not to mention the precision of individual components, the company also excels in making adjustments while putting them together. Many astronomical telescopes are one-off tailored products, i.e., limited to only one worldwide. Nishimura’s know-how to assemble them at their locations of installation forms the core of the company’s unique technology.