ASTRONOMICAL NOTES

Evening Star, Issue 20421, 28 February 1930, Page 2

ASTRONOMICAL NOTES

THE SKIES IN MARCH [Written-by A. G. C. Crust, M.Sc., for the ‘ Evening Star.’] POSITIONS OF THE STARS Sidereal time Bb, latitude 4(kleg S. Tho following positions bold for March 2, at 10 p.iu. (summer time), and tour minutes earlier each succeeding day till-the change to standard time takes place on Sunday, March Id. Tho positions then hold for 8.30 p.ra. on March 17 ami 7.30 p.m. on April 2. In tho north shine the heavenly twins, Castor and Pollux, the yellowish Pollux being 16deg above tho horizon, while tho bluish Castor is rather lower and a little to tho left. These are the chief stars of the constellation Gemini, the Twins, and Castor is a celebrated doublo star to the telescope, both of its components again being very close doubles, only detected by tho spectroscope. North-east by north and 2ddog high shinßs Hegulus, the bluish star of the Lion. Hanging down from Hegulus is the sickle-shaped group eff stars by which Leo is so readily recognised. Due oast, at an elevation of 15dog, shines Spica, tho harvest star, in the constellation of tho Virgin. Spica is a doublo star only to bo detected by the spectroscope. It is so remote that its light tabes about 220 years to reach us, and its two components bear a striking resemblance to the telescopic pair forming Alpha Crucis, in tho Southern Cross, which now lies southeast, at an elevation of SOdeg. Alpha Centauri, the bright pointer to tho Cross, is now south-east by south, 35deg. Just as the so-called Pointers guide ns to the- Southern Cross, we find that Spica also has a pair of pointers in the little constellation Conus, the Haven. The principal stars of this group form a quadrilateral like the mainsail of a yacht, tho gaff pointing straight at Spica, a few degrees below. Almost level with Alpha Ccntauri shines Achcrnar in tiio south-west, while the brilliant Canopus is south-west by west, 73deg, tho highest bright star. Rigel is north-west by west, 37deg,_ Aldebaran north-west, 12dfg, Alpha Orionis northwest by north, 29deg. This red star has been exceptionally bright this summer, its magnitude being sometimes equal to that of Rigel, 0.3. Twentyeight , degrees above Alpha Orionis shines the brilliant bluish star Sirius, a fact which will help readers to follow the elevations given in these notes. Procyon is north by west, 31)dcg. Like Pollux, Procyon has a dimmer star below and to the loft, though the difference in brightness is much greater.' This dim star was called by the Arabs “Gomcisa,” tho “dim-eyed.” The moon’s position on March 7, at 0.40, is north-west, 4cleg, and on tho Bth sho passes the red star Aldebaran at 4 a.ra., first quarter being reached at 4 p.m. At 4 a.m. on the 11th the moon passes Pollux, on tho 13th at 1 p.m. Hegulus. Full moon falls on tho loth at 6 a.m., and at 6 a.m. on the 17th tho moon is alongside tho star Spica. The planet Jupiter may he seen alongside tho moon on the evening of tho 7th. On the 12th, at 9.20, tho moon’s position is north-north-oast, 21deg, and on the 17th, at 8.30, east, lOdcg. Last quarter falls on the 22nd, at 3 p.m., and new’moon on tho 30th, at 5 p.m. Tho position of tho planet Jupiter for our epoch is north-west, Bdeg. Tho autumn equinox occurs on tho 21st at 8 p.m., when tho sun crosses the equator into tho Northern Hemisphere. CITY STREET DIRECTIONS Dunedin readers may locate the following heavenly bodies from the Queen’s Gardens, Lower High street: — Hegulus, a little to tho right of tho line of Cumberland street, looking north, and at a moderate elevation; Pollux, rather, low, .between Burlington and Cumberland streets; Spica, at the same' elevation, between Rattray and High streets, eastwards over tho railway; Alpha Ccntauri, on tho line of Burlington street, produced southwards; and Alpha Orionis, in the opposite direction, and almost as high, Sirius being twice as high in the same direction. On the 12th, at, 9.20, tho moon will shine along Cumberland street.

SOLAR INSTRUMENTS, ANCIENT AND MODERN Tho dependence of terrestrial phenomena upon the movements ot the sun was, and still is, mie of the fundamental subjects of strictly scientific inquiry, under-running all the superstitious rites which often lent popular interest to the earlier observations. One may realise how far even the most primitive astronomers progressed, when ono knows that tho Australian aborigines have given names to some of tho brighter stars. The humble beginnings of our own practical astronomy may be traced to the nomad shepherds of Western Asia, of tho early Turanian races, which preceded the "Semites, and wore the ancestors of tho Mongols and tho Turks, These shepherds, as we have pointed out, had no groat love for tho scorching sun, but they found that there was a useful relationship between tho movements of their celestial enemy and the periodic droughts and floods which influenced their own migrations. This' relationship was probably first noticed by a chief or medicine _ man, who studied the varying length ■of the shadow thrown from a long spear thrust vertically into the ground. As the sun rose higher and higher at noon each day, the shadow would grow shorter, till tho season came when feed was scarce in the desort and tho tribe had to migrate to better watered lands. Of course different phenomena would ho of interest in different countries. In the Syrian desert the summer drought and winter rains;*in Palestine the so-called “ former ” and “latter” rains; in Egypt and Assyria the flooding of tho great rivers and tho dry seasons most suitable for brick-making, might all ho predicted with tho help of tho vertical son pointer. 'The ancient astronomers knew tho stars and could divide tho night into hours or watches by observing tho progress of the constellations across tho sky. Also they could toll tho seasons by the stars which rose or set with the sun, thus using tho horizon as an instrument, and many of tho pillars at places such as Stonehenge seem to have been erected for such purposes. By watching tho sunpointer at dawn and at sunset, they could obtain a clearer idea of tho sun’s position among the stars, anti by watching tho movement of tho shadow through the day, they could divide the time into hours almost as well as at night. Tn gre.it civilised countries, such as Egypt, tho simple idea of tho vertical spear was elaborated, and probably tho Pyramids illustrate its highest development. These mighty instruments thus

watched over the life ami happiness ol : the Egyptian people, warning the priests of the Hoods of the Nile, and ministering to the worship of their justly rovered deity, the 'sun god Ha. Tho ancient Peruvians used quite a small vertical pointer, surrounded by a circle of masonry, on which were placed tho necessary marks, to determine tho solstices and equinoxes, all of which were celebrated by appropriate religious festivals. 'this instrument was “Tho Sun God’s Halter,” the “ Intip Huatana.” Tho use of the vertical pillar as a sundial was superseded by tho invention of tho astronomer Pytheas, of tho ancient Greek colony at Marseilles, who used a sloping pointer directed towards the north polo of the heavens, and easting its shadow upon a horizontal surface. In such an aparatus hours of equal duration could bo marked on tho dial by means of a simple calculation. Tho idea that a sundial is an out-of-dato and purely ornamental instrument is entirely erroneous. Tho clock has yet to he made that can ho left out in all weathers, never wound, cleaned with a hose, and whoso rate _ can bo relied qpou indefinitely, and indicated by a permanent table. Who could wish for a bettor or more instructive timepiece, ornamental, practical, and correct to the nearest minute? Mr J. Stewart, of 99 Bowmont street, Invercargill, has made a hobby of sundial construction, and his craftsmanship is as excellent as his the netical ’ knowledge is sound.. Wo understand that ho wishes to sell his stock Sd’ dials, and wo recommend all who wish to obtain a thoroughly reliable timepiece of an attractive pattern to communicate with him, _' The sun dial is perhaps the most remarkable of ’solar instruments. Tho vertical spear, tho obelisk, tho Intip huatana, and the Egyptian pyramid are its distinguished ancestors, and its modern cousin is the meridian circle, of surpassing accuracy, while the great telescopes of modern observatories, with their attachments, arc all erected on the principle laid down by tho immortal Pytheas, the invpntor of the sloping gnomon which first divided tho day into equal hours.