ASTRONOMICAL NOTES

Evening Star, Issue 21220, 29 September 1932, Page 3

ASTRONOMICAL NOTES

THE SKIES IN OCTOBER, 1032 [Written by A. G. C. Crust, M.Sc., lor the ‘ Evening Star.’] POSITIONS OF THE STARS Local sidereal lime 2-1 hours. latitude •iCdeg. S. The sidereal time {liven above coincides with .11.30 p.m. on October 2. and with suecc'sivo epochs tour minutes earlier each day till 11.00 p.m. on October 8. Alter the change to summer time, the stars may be looked lor in the same positions at 11 .-12 p.m. on the ihli, II.OU p.m. on the 17th. and lU.t'U p.m. on Novcmbc,' i. The Moon will occult the iaiut star 110 H Seorpii on October 1. the star disappearing at 9.13 p.m., while Alpha Seorpii. the red giant Antares, mag. I.:?, will disappear behind the Moon at 9.50 p.m. the sane evening. First quarter will occur on the evening oi the 7th, and at 11.10 p.m. the Moon will he situated duo west, elevation GGcleg. Having passed south of Saturn on the evening of the Bth, and 22deg. north of Fomalhant on that of the Till), the Moon will be N. by W'., 45deg., at 11.20 p.m. (summer time) on tho ]2tb. and lull Moon will occur early on the 15th. On October 17 the Moon will be N.E.. Gdog., at 11.00 p.m., and the reappearance of the faint star 11 Tanri is predicted lor 4.07 a.m. on the 18th. After passing lldog. north of Aldebaran on the morning of tbe 19th the Moon will cover the star 22 Aurigae. wliiclt will reappear at 1.59 a.m."on the 20th. Last quarter having occurred on the morning of the 23rd. the Moon will pass Jupiter and Venn? on the 201 b and 2711 t. will ho new early on the 30th, and pass Mcrcui">' on the 31st.

The following are the principal stars visible at 24 hours, S.T.:—

Alpha Crncis is due south and ISdcg. above the horizon, while Alpha Ccntaun is S.S.W. 21 dog. Antares is now situated S.W. by W.. 4dog.. Altair W.N.W.. 12deg.. and Fomalhant N.W., 70deg. The brilliant summer constellations are now beginning to rise in the east. Aldebaran being E.N.E. 2deg., Rigcl E. 14deg., and the brilliant Sirius E.S.E. 5 dog. We propose to describe some of the constellations in this region in detail in the next and following months’ notes. The highest bright star is now Achcrnar, S.E. 72deg.. while Canopus lies 33dog. above the horizon in the same direction.

The planet Venus will pass Neptune on October 1G and Jupiter on the 20th. very close in both oases. Observers will probably be able to identify all throe bodies in the early morning sky about these dates. Neptune, of course, requires a telescope. The (inly planet visible at 24 hours, S.T.. is Saturn, situated W. by N. 3G dog. His brightest satellite. Titan, will reach greatest elongation west at 1 li.ui. on October 12, and 12 noon on October 28.

From the Queen's Gardens. Dunedin, at 24 hours, S.T., Altair will bo. seen very low in the direction taken by Dowling street. Aldebaran in that taken 1 Lower High street. Sirius opposite to Altair. and Alpha Centauri in the direction taken by Vogel street. All these slars arc very low, except Alpha Centauri.

CLIMATE AND THE DEVELOPMENT OF ASTRONOMY

The most ancient constellation ligurcs indicate the kind of climate in which astronomy originated. The animals include the lion, horse, ram. and goat, and the herdsman is one of the oldest human figures pictured in the sky. From their internal evidence and the ancient monuments these figures have been traced to a nomadic race living in the hot. dry country of Upper Mesopotamia about 7.000 years ago, and the stars probably guided those people in their migrations.

Observatories and various kinds of astronoinieal instruments were developed earliest in Assyria and Egypt. These were hot, dry countries, with abundance o( clear skies; and so was Syria, whore the Phoenicians developed the art of navigation. The astronomical science of these lands was, however, very largely observational in character, and 'though their astronomers made remarkably exact determinations ot the various solar year periods and lunar months, they do not seem to have attacked the theory of the solar system in general with any success, and what understanding they did have in these matters seems to have been darkened by astrological superstitions.

In America the Maya civilisation used an elaborate calendar system since about 600 n.c. Except for the wet, temperate, elevated region of Guatemala, the Maya area now has a hot. wet. tropical climate, but must surely have been much drier in the great periods of high civilisation. Though evidently great observers, the Maya astronomers excelled in mathematics also, and stem to have “ kept track v of the planets with great success.

'I he great thinkers ol muicpiity. in the Old World, wore the Greeks, but in astronomy especially their ingenuity seems to have far outrun their skill as observers. \\ ith hot. dry, clear summers, but wot winters they enjoyed a more temperate climate than did either Egypt or Assyria. Aristarchus of Samos discovered that all the planets, including the earth, revolved around tile Sun, and had the Greeks been better observers they would probably have accepted this .simple idea, instead of the complicated theories of epicycles which assumed the planets to revolve in circles round invisible centres, which in turn revolved around the earth. The whole record of ancient astroTionty, as of other sciences, is disappointing, for nowhere, unless in M ayah, do wo find that close and healthy interaction of theory and observation which is so vital to true science, and superstition lay like a blight upon many aspects of the subject The Roman? neglected astronomy, and later the barbarism ol the Dark Ages closed down on European science in general. In the East, however, (he Middle Ages wore a time ot great activity. The followers of Islam absorbed much Greek learning, especially at Alexandria. and those sous of the desert proved skilful observers also. Jn Persia and Turkestan A 1 Sufi and Ulugh Heigh, two most accurate observers, did much original work ; in particular they improved the system of stellar magnitudes -invented by Ptolemy. Egypt, Arabia, and Spain all contributed important work, the tables worked out by King Alphonse being used for many eon tunes afterwards in Europe.

From about the Fifteenth Century astronomy nuulo rapid strides once more, this time mainly in the wet temperate climates of north-western Kuropo, and it was hero that the thinker and the observer at last came into fruitful and effective alliance, typified ■ ; ■ the joint labours of Tycho Hrabe ami Kenler. ('onei'iiic’.i'-. Newton. red a h;-1 of other i-cebcatrd ire- ai c.m-■ come m ui'ml. uo'tlv ill that moi't tiunporatc area ol Iv.irope. which MU! nrodueos the world's deepest sclent die i b inkers.

Astronomy was of great interest and importance 10 the adventurous imriga-

tors of Western-Europe, who. in turn, led to the establishment of the science in varying degrees throughout the world. ' For ages astronomy had flourished in the countries with a monsoon climate, with generally hot weather but dry winters and wet summers —e.g., India and China. The peculiarity of the astronomy of those regions is notjibly its connection with religion, hut here again superstition has an adverse eliect. European penetration. in India especially, Juts given a fresh impetus to tue ancient science, and Indians have proved themselves both good observers and clever thinkers. it is to be feared that astronomy wili never llourish. however, in those climatic zones where the weather is alwavs hot and humid—e.g.. " Central Africa, Northern Brazil, and many island of the Pacific and the Indies, The weather is always more or loss cloudy, and die climate 100 enervating lor serious study. Similarly, in the Pylai regions it i-.> always cold, pi ten very cloudy, and too inhospitable ior permanent settlement. Expeditions in those regions devote their attention mostly to phenomena that must be observed locally, ,-ome ol which arc quasiastronomical- —e.g.. aurorae, haloes, and the zodiacal light.

The expansion ol European astionomy in the Seventeenth Centum "as greativ helped by the invention ol the telescope. This' instrument, and the telescopic camera and spectroscope developed in the Nineteenth Contnij. have made ever more urgent the chccts of .suitable climate upon observation. In hot, dry. clear lauds, observation is relied upon much more than prediction—e.g.. in Arabia the now Moon of Ramadan is still fixed by ‘direct obstarvation. Iho advent ol bad weather thus sometimes causes dilierent to" ns to beciu the fast on different dates. The astronomer of the moist, cool climates. on the other hand, cannot >e at all sure of the weal her. and nonce is more inu rested in the art ol piediction. In the strictest practical sens.. 1 astronomy is concerned only with pi edieting the positions ol the Stars, and determining the time Irom them. I lius the British,' French, and German Governments erected observatories, "itu telescopes, close to their capital cities, rather than whore the climate would have permitted more continuous and frequent observations. Ibe telescope bad vastly enhanced Die accuracy ot ’ Pie practical ."' ol k ' lint it had also shown iresh worlds to conquer, and no science could a (lord to rest content with merely practical achievement in such stimulating eucumstanees. The- true teloscopist and star-lover soon louiul that even apparently good, clear weather shpwct. astonishing variations allecting the appearance of the planets, for instance. The planet Mars on one night might appear hazy, featureless, and shapeless, but on another night there would be enough detr. 1 to satisfy any observer. When llm spectroscope and camera fame to be applied in the sun and giirs sit-iilar ariatiotis persisted.

Tin,'. in quite modeni i iiiies. astronomers liave shown a marked iniere t in '-linnii.il.- dii'i'eivm-e-p. and in the newer eounlrii-,- especially, the great observatories whose task is most pureiy to “ observe ’ : ba.c. been located in

climates more resembling that where astronomy began, the time-keeping institutions still being maintained mostly near the capital cities, where also most of the important mathematical work j s { | one —e.g.. the compilation, of the ‘ Nautical Almanac.’ In Europe, mountain sites arc generally favoured for observatories, though not indeed the high, snow-covered peaks. Where desert mountains arc available, they are generally to he preferred. Low rainfall is associated a 1 wavs with little cloudiness, though not 'always in the same proportion. Again, mountains rise above the dust, .smoke, and mists of the plains, as well us the thicker layer? of cloud, and also permit the astronomer to look at the stars through a smaller thickness ol air. The higher layers of air are not disturbed by the friction of the wind against the ground, nor by the intense heal hut and cooling ol the plains, and though the winds are often strong up there, they glide over the lower strata of air without much disturbance. Thus, the frictional effect, or " turbulence " which so disturbs the images ol stars 'and planets, is minimised by observing from a mountain top.

The temperature changes in a dry continental climate arc especially annoving to the astronomer with a large reflecting telescope, as they affect the curvature of the great mirror. Here again, the mountain top is preferable to the arid plain, for its temperature is equalised bv every breeze, and though it, iimv become rather hot on a calm dav, its heat cannot compare with that of'an arid valley tinder a blazing sun, nor it= coldness with the extreme rigour of the same valley on a calm, starry night. As the. air is drier and cleaner the higher we ascend, both dew and dust, are less serious on the top ol a mountain. A high range of mountains at a considerable distance helps te shelter the observing site even from winds at a Treat height—e.g.. the Andes Dialler the solar and astro-physical observatories of California. Chile, and Peru iu this- wav, and the Southern Alps would ’similarly shelter the sites in Central Otago. There is a tendency for winds to blow up the slope ol a vaime or the scarp of a plateau by day. amfdown it by night, in fine weather. As this would disturb the air ami likewise make the temperatures more extreme, isolated mountains make iinirli better sites for astronomical purposes, for on solitary peaks (hose wind effect? are negligible.

In recent times we ilioretore find that though government and learning alike tend to centralise in wot- temperate climates, in America and Uussia also, where there are wot. cold winters, astronomical observatories are pushed out boldly into the desert and steppe climates, wherever a suitable mountain can be found —e.g.. Mount ilson, in California. There are considerable advantages in having groat obsem atones in extreme altitudes, ami this is comparatively an easv matter in the Northern' Hanii-phere--- e.g.. in llu.-sia ami 'Canada., 'ml in the Southern Mcmi'phere. observatories stop short about liodcg south of tl’.e Centra Otago oilers a very suitable climate ami a sin table topography at dodeg S, 'I he only -possible competitor is Patagonia.

a much less developed country, whose climatic conditions even are seriously challenged by those of Otago.