FLANS FOR VAST TELESCOPES

Evening Star, Issue 19444, 30 December 1926, Page 11

FLANS FOR VAST TELESCOPES

SOUTH AFRICA MAY GET ONE

SIX-FOOT PHOTOGRAPHS OF THE MOON.

It is possible that South Africa will in time to come possess one of tho world’s largest telescopes.

Dr Henry Norris Russell, Professor of Astronomy at tho Princeton University, tells in tho ‘ Scientific American that astronomers have planned a monster telescope, many times greater than the greatest now in existence, and that actual construction only awaits the necessary funds. He is of opinion that three enormous instruments, of the type described below, ought to be built —one for America, “another on British soil, perhaps in South Africa,” and a third probably in French Algeria. The proposed telescope will have an aperture of 300 in, and the focal length will bo IjOOOin. Tho skeleton tube will bo 6Sft in length over all, while the outside diameter will be 35ft. A secondary convex mirror of lOOin in diameter will be used in most cases, but the primary locus at the upper end of the long tube will also be used. The lOOin mirror will reflect the rays back to the focal end, giving an imago on the scale which corresponds to an “equivalent focal length” of 200 ft. HUGE MAGNIFICATION. Tho moon will appear nearly 2ft in diameter with this new arrangement, while Jupiter will appear more than 4in across. Photographs of these could be enlarged to three times this size by lenses acting after the fashion of tho familiar telephoto combinations. The exposure time for taking these photographs will be shortened considerably. i'iie ugiu will pass through the centre of the mirror like the “Cassegrain Form,’ and the observer will stand at the lower end of the telescope, looking up towards the sky. The proposed telescope will have auxiliary, instruments such as a spectroscope, photometer, thermocouple, for measuring heat and the like, permanently attached to the lower end, and a simple diagonal reflector will be all that is necessary to throw the light out to any one of the instruments. This new method will save a great deal of time and energy, and. a new star might bo observed iu several different ways on the same nightOn the usual telescopes of to-day the observer is forced into many inconvenient positions, since the observing platform follows the lower end of the telescope around. The proposed telescope will have mechanism so devised that there will be no such difficulties. The main tubs will be mounted in a great forked polarlaxis, enabling the observer to obtain a view of every possible part of the heavens. The weight of all moving parts together will lie the startling figure of 1,600 tons. Roller bearings will ease tho handling of tho heavy load, while the necessary precision of running will be attained by precise construction. COSTLY UNDERTAKING. The cost of the great telescopes, with doiuo unci accessories, is estimated at about £2.250,000. The dome would have io he 200 ft in diameter and 200 ft in height. The dimensions of the cupola will be twice the size of tho 100 m Hooker telescope. Its location is doubtkss tho greatest problem. Many considerations must be borne in mind, -such as clear skies and steady air, while the staff must have tolerable living conditions and accessibility of engineering and machine shop aid, and, especially, stability both of the material foundation against possible earthquakes and of the governmental environment against possible wars or revolutions!

A location iu tho Southern Hemisphere would be decidedly preferable, as the most interesting region in _ the whole heavens would then be accessible. The cost certainly will be enormous, but the £IOO,OOO which has been actually spent on the Hooker telescope would have seemed equally impossible of attainment a score or so years ago. The investment, however, would bring in largo dividends of increased knowledge from a scientific standpoint, and it would bo a permanent one.