Radio age (Jan 1927-Jan 1928)

RADIO AGE for September, 1927 27 10 O INCH TELESCOPE AT MT.MLSON -LARGEST IN THE WORLD MISS LIBEF?TV 12 MILLION DOLLAR TELESCOPE If I FEET PLANNED BY HIGH F*. Gr. RE/^cSE servatory, of the University of California, has one in Chile. Here are observed stars that are invisible in California. The observatory of Harvard University has had a branch since 1889 in Peru. Now they are moving to South Africa, where conditions are better. Largest Southern Telescope At this branch will be not only the instruments from Peru, but also some new ones. Chief of these will be a great reflecting telescope with a mirror five feet in diameter. This will be the largest telescope in the southern hemisphere. It is already being constructed in a plant in Pittsburgh. This is the same plant that made the six-foot mirror for the big telescope at Victoria, B. C, the largest outside of the United States. Like all reflecting telescopes, this great instrument will have a mirror which takes the place of the convex lens in the telescope of most familiar type. The mirror is dish-shaped, and faces the stars. It is at the bottom of the telescope. The light of the star is reflected back from it, and a smaller mirror at the top of the telescope reflects the light to the side. Here it can enter the eye of the astronomer or fall on the sensitive photographic plate. The Harvard astronomers will have company, even though they are so far away from home. Within the last two years the University of Michigan and Yale University have established branch observatories in South Africa, but at both of these stations are refracting telescopes, not reflectors. There are other reflecting telescopes in the southern hemisphere, though not as large as the new Harvard one. Nearly a century ago, the great English astronomer Sir John Herschel, took his great 4-foot telescope, at that time one of the largest that had been built, to the Cape of Good Hope. He was the first astronomer to use a large instrument in southern latitudes. From his researches arose the British Royal Observatory at the Cape. Australia also has a big reflector. This is a more modern instrument than Sir John's, for it was built in 1870. Its mirror is also four feet in diameter. This year it has been overhauled for use in observing Pons-Winnecke comet. $12,000,000 Telescope Planned But all these instruments fade into insignificance before a telescope that has been planned by F. G. Pease, designer and constructor of the 100inch Mt. Wilson telescope. According to Mr. Pease, the principal item necessary for the construction of this monster research instrument is the cost. Twelve million dollars, he esti mates, would provide it. A large amount, of course, but only about a third the cost of a modern battleship ! And how much more good would the telescope do for the world than the battleship, for it would increase man's knowledge of the universe about him ! There are mechanical difficulties to be solved before such an instrument could be made, it is true. However, Mr. Pease probably knows more about such matters than any man living. This is what he says : "The question has often been asked 'How large a telescope can be built today?' My reply would be that anything up to a hundred feet in aperture can be built provided one wants to pay for it." One of the problems to be solved is the material of which to make the mirror. Present telescope mirrors are mostly made of glass. On this is coated a layer of silver to reflect the light, much as in the ordinary looking glass. The chief difference is that the telescope mirror is silvered on the front instead of the back. Hold a coin to your looking glass and you will see. the reason. In the glass you see two coins, one bright, reflected from the silver on back, and one faint, reflected from the glass surface. In astronomy such a double image would be a serious defect.. So the silver is coated on the front, and