WORLD'S LARGEST TELESCOPE.
In man’s efforts to conquer space and ! bring the celestial bodies within range ■ of vision, so that be can study them j and learn something about the wonder* joi the heavens, he has built many j mighty telescopes. The biggest of t them all is undoubtedly the famous j Yerkes telescope, the pride and glory 1 of the Yerkes Observatory, at Williams j Bay, in the American. State of Wis--1 con sin. I' Some idea of the size and tremendous J magnifying power of this enormous in- | strurnent may bo gathered wheu it is | stated that it is '24 yards, long, and I weighs, with its iron pedestal and ma- ! sonry, 75 tons, and was built at a cost |of nearly £250,000. It claims to bo the largest refractory telescope ever constructed, but it is by no means this distinction alone which entitles it to rank as the foremost telescope in the j world, but rather its wonderful magni- ' lying power. Here it should be explained, perhaps, | that there are two distinct kinds of i telescope—refractors and reflectors. In 1 the first of these you look through a j convex lens at a star, while in the latter you merely see the reflection of the star in a concave mirror. The instrument under notice is a refractor, and wo get an idea of its power when it is | remembered that it virtually brings the I moon to within thirty-seven miles of the earth. If there were buildings upon tin# satellite as big as our cathedrals, the Yerkes telescope would quickly announce their presence. Then, as an astronomer onoe remarked, ‘the way it picks up stars is a caution.” The first thing the builders did was to erect a special tower to house the instrument. It possesses the largest movable roof in the world, and the I building of this dome is rightly regarded as a clever piece of engineering work. It is 90 feot in diameter and over (30 feet high. The wails of the tower terminate at a height of 52 feet from the ground in a heavy stone coping, on which is erected the circular track upon which the dome revolves on 36 wheals, each three feet in diameter. Sitting at the eye-end of the instrument the astronomer has only to press a button when the dome will revolve and reveal that portion of the heaven* desired. The tube of the telescope i# made of sheet steel, is GO foot in length, and weighs six tons. Cranes and powerful ‘ tackle had to bo installed to lift it into j jKJsltion. The diameter of the tube at I the eye-end is 38 inches, while at the centre it is 52 inches, and 42 inches at i the objective end. it varies in thiok- | ness from 7-32 of an inch at the centre Ito of an inch at the ends. It is absolutely (lawless along its whole length, and when speaking of “11awe” in a 60foot toiwjoope we have to remember that an error of the ouo-thousaudth part of an inch would be serious. While taking observations the position. of the eye-end of the telescope is, of course, altered when the instrument is moved up or down the slit in the dome. lu order, therefore, to enable the astronomer to watch the heavens at varying altitudes, the whole floor of the tower is so designed that it can i rise or fall to any desired level. This I rising floor is of steel construction. 73 I feet in diameter, and weighs about 88 ! tens. It is worked by electricity, and * by means of a switch the astronomer j can bring the floor io any height. | The most important part of the whole instrument, howov<*r, its 40-moh ob-ject>-gla.ss, and, unload, this niaj truly ho said to be its crowning glory. It was made by a Pans firm. Tin, crown lone is about two and a-half inches thick at the centre, and three-quarters of an inch at the edge, and weigh* 200 pounds. The flint lens, which is separated from the crown glass by a distance of eight and three-quarter inches, I weighs over 300 pounds, and is one i and a-lialf inch thick iu the centre aud j ;wo inches at the edge. These lenses represent the work of years, and cost over £13,000. The difficulty of work of this kind will bo ' better understood when it is stated that it is often necessary, in tho manufacture t of leasee for large telescopes, to grind 1 the glass so finely as to take away ft twenty-thousandth paxt of an moil. - &uoh minute work involves many pro- [ cesses, and. often result* in failures and | delays through the breaking of the 1 glass. , , ~ | So extremely flue is the lens hi tfia Yerkes telescope that every ray of light passing through it is brought to a focus twenty yards distant at a point small enought to be covered by the point *fe j the end of this sentence. The lenses are ! mounted on aluminium bearings, and ! in their cell of steel weigh close on hall I a tou, and can boast of a circumference | of three and a-half yards. [ Equally marvellous is the electrical 1 apparatus installed for working the telescope, Everything in connection with the instrument is manipulated by electricity. At the eye end of the telej soopo thore is & ]&rgo keyboard, which is connected by means of numerous wires to tho electric motors concealed in the machinery. To raise or lower tho largo tube, all that the observer has to do is to press a button, while the depression of another key causes tho huge instrument to paint in any desired direction. The pressure of a button, too, will cause the roof to revolve and leave the astronomer in full view of tho sky. When Professors Hanksley and Jaussen, two well-known astronomers, declared that life existed on the moon, the observers at the Yerkoa Observatory wore able to show that the surface of this satellite is composed of extinct volcanoes, and there being no trace o water, air, or vegetation on the moon, it was impossible for life to exist there.
Permanent link to this item
https://paperspast.natlib.govt.nz/newspapers/DUNST19130804.2.6
Bibliographic details
Dunstan Times, Issue 2677, 4 August 1913, Page 2
Word Count
1,032WORLD'S LARGEST TELESCOPE. Dunstan Times, Issue 2677, 4 August 1913, Page 2
Using This Item
Allied Press Ltd is the copyright owner for the Dunstan Times. You can reproduce in-copyright material from this newspaper for non-commercial use under a Creative Commons New Zealand BY-NC-SA licence. This newspaper is not available for commercial use without the consent of Allied Press Ltd. For advice on reproduction of out-of-copyright material from this newspaper, please refer to the Copyright guide.