IN STARRY SKIES

Evening Post, Volume CIX, Issue 56, 7 March 1930, Page 16

IN STARRY SKIES

(By "Omega Contauri").

EXPLORING THE HEAVENS THE TELESCOPE OF THE FUTURE

The cry of.- the astronomer is continually for more and more light. From every luminous body in. the heavens, radiation is for ever streaming out and traversing in every direction the vast abysses of space. But the light from any source diminishes lin intensity according to the square of the distance. If, of two equal stars, one is a thousand times as fa:1 off as the other, it will appear but one millionth as bright, and the differences in celestial distances are inconceivably greater than this. Our nearest stellar neighbour is about 275,000 times as far off as the sun, ana stars near the boundary of the galaxy may be 40,000 times as far away as that. Then far beyond the utmost limits of the Milky Way are the unnumbered hosts of the spiral nebulae. The very nearest of these is six times as far away as the most distant star in the' galactic system. The great Hooker telescope can just photograph objects lying about

150 times as far away as that. One great problem that the telescope of the future has to solve is what lies still further off in the "Great Beyond." The only possibility which we see at present of exploring the wonders hidden in such vast recesses of the Universe depends on an increase in the light gathering power of our instruments, and hitherto an. insuperable obstacle has been , the impossibility of casting larger discs of flawless glass. We have seen how Professor Eitehey is overcoming this difficulty by building up the necessary discs out of numbers of glass plates. This photograph shows one of the many turntables, each ten metres in diameter, which the Saint Gobaih Company use in polishing plate glass. The inspector, kneeling at .his work, gives a good ideaof the size; In the super-telescope, which is now.planned, the plane mirror of the coelostat is to be the full size of this turntable. Each of the five interchangeable concave mirrors will be eight metres or. 26.25 feet in aperture. It is clear, that it would be unwise to attempt to make the whole of an instrument of such dimensions move as it follows the motions of the heavenly bodies. A fixed 'type of telescope has therefore been determined on. This necessitates some loss of light in two additional reflections, but the advantages gained far outweigh this losa. The only part that has to move during the prolonged exposure of a photographic plate is the great mirror of the coelostat. This is mounted with its plane; parallel to the polar axis to which it is attached, and it turns once in 48 hours. The reflected image is thrown in a direction which depends.on the declination of the ob-

ject. But the reflected beam of light is caught by a second plane mirror and sent in a fixed direction down the great square tube that occupies the centre of the observatory building. This arrangement will make the work of the observer far more efficient. Instead of climbing to all sorts of precarious positions high in the air, he will work in as comfortable a posi* tion as he would occupy at his desk in a library. This will enable the increased power of the instrument to be used to the fullest extent. Professor Ritchey tells us much of what we may expect. At the best observatory sites it is possible to see with the unaided eye stars of magnitude CD. With a telescope of 40inch ■ aperture, such as the greatest existing refractor, it is possible to observe visually stars ten thousand times fainter, that is of magnitude 1G.5. To. detect visually stars 100 times fainter still, of magnitude 21.5 the aperture of the telescope would have to be 33 and l-3rd feet, whilst to sco stars of magnitude 26.5 would require an aperture of over 330 feet. Fortunately photography enables us to secure the same result with much smal ler instruments. Professor Bitchey in 1910, using an aperture 50 inches in diameter photographed stars of magnitude 21.5. " With his new 5-metre telescope he expects to photograph stars ten thousand times as faint. The 8-metre telescope should reach stars a magnitude fainter still. The photographic plates are so much improved and the methods of manipulating the instrument have been so carefully de veloped, that the resulting photo graphs will be,ar considerable enlargement. The theoretical magnifying

power, as calculated by Professor Bitchey, is 22,500 diameters for bodies having extended surfaces. This means that details less than two miles in diameter will be visible on the surface of Mars, and objects only 70 feet across on the Moon. For star fields, such as those of the Milky.Way and the Spiral Nebulae, the magnifying power will be much greater reaching the astounding figure of 37,000 diameters. The photographs obtained with these great instruments are to be available to workers of every nation, not only for scientific research but for the purposes of popular education, The splendid increase in the intellectual outlook thus secured will be of immense benefit to every country which; shares in it. Now is the time for New Zealanders to be. busy. Let us determine to be amongst the first to secure one of these magnificent instruments. So far only 255 people have answered our appeal and banded themselves together in the endeavour to secure success in this great enterprise, and so turn our dreams into a' glorious reality. The Government Astronomer of New South Wale 3 has given his very warm approval of this scheme, and Professor Eitchey himself has written a most encouraging letter in which ho says that we can undoubtedly do very much to aid the project that he is endeavouring to bring into existence. Next week we shall show a picture of his projected observatory, and if each of the 250 odd members of our Society can succeed in inducing a few more to join, we shall have the thousand who are to be entitled Foundation Members. ■, If each of these can find a thousand more .'he N.Z. Observatory will be in sight..