ASTRONOMICAL NOTES FOR SEPTEMBER, 1915.

Pukekohe & Waiuku Times, Volume 4, Issue 76, 30 August 1915, Page 4

ASTRONOMICAL NOTES FOR SEPTEMBER, 1915.

(Contributed by Mr L. J. Comri?.) THE SUN. The sun's path this month is through the consultations Leo and Virgo. On the 24th, the day of the equinox, it crosses the celestial equator, and the day and night are each exactly twelve hours' long. On that day it crosses ths meridian and reaches its highest altitude at 11.43 a.m. by cur clocks, which do not keep local time, but that of the longtitude of Chmtchurcb. It will be remembered that when this altitude is subtracted from ninety degrees the result i% the latitude of the observer. I meution this because some of my yo:ng«r rsaders may f«.el disposed to measure the altitude on that day. At tte beginning uf the month the sun rises and sets ten degrees to the north of tne cast and west hue; by the 24th it rises due east and sets due west, while by th<; eid if the month it is aheadv three degrees to U.c sojli:. J warder how many reoplvs have i.otic-.d that the UilUht i* lovger at s mc period* uf the y"i.ar than at other*. There sic two o canons each year when the twilight i 3 sh'.rtes!; one if these cccurs (in Auckland) nn September 10th, or thereabouts, of each year. ItlE MOON. Tr.e phases of tbe mcon are as follows: - Last quarter Sep. 2nd 2 27a.m New moon Sep. 9th 10.23 p.m. First quait.r Sep. 16th 6.51 p.m. Full moon Sep. 23rd 9.5 r.m. Last quarter OC. Ist 9.14 p.m. Apogee, September 2nd, 9 a.m., 251,200 mil's. Pt-ruff, S.ptember 15th, 3 a.m., 229,500 mil s

Apogee, Sit ruber 30tb, 4 a.m., 251,400 miles. 1 would like to expose a fallacy concerning the moon. There is an eld saying, "When the moon is on its back we shall tnve rain." The cMi'cction between tbe two probably arose fiom the tact that the moon is awlajs on its back in spring, whereas the tn.iy season ociuis at the same time; but it is nol to be imagined that tbe aspect of the moon has any irfluenca on the weatner. The reason why the moon is in this po iiion in spang may be seen when we consider that the centre ot tbe bright limb is naturally directed lowa ds the source of illumination—the buh—and in spring it so happens that tbe moon is more nearly vertically over the sun afie: sunset than it is at any other time daring the year. The full moon at the vernal equinox behaves in exactly the opposite manner to tbe darvest Moon al the autumnal equinox in that it lises very much later each night. Fur instance, in the foar day 3 from March 30th to April 3rd of this year the time of rising tf the moon was extended by only two and a-quarfer hcurs, whereas on September 28th it rises nearly f.itr and a-quarter hours later than it does four nights previously. The times at which it rise?, and its angular distance trom the east towards the north, on the dat.s immediately after full moon are as follows:

For the first week of the month tbe moon will be seen only in the mcrning. It happens that it uses almost at the instant that the month commence?, and for the first morning may be seen above the Pleiades. On the morning of the sth, it will be in Gemini, to the north of the two planets Mars and Saturn. The following morning it is near tbe Twins, Castor and Pollux. On the evei.ing of the 12th, when three days old, it will be clcse to Spica in the Virgin. Three nights later, on Wednesday, 15th, there will occur an exceedingly interesting phenomenon--an occupation of Autares, the bright red star in Scorpion. After sunset the moon will be seen below the sta', which it gradually approaches, uctil at 8.20 p.m the dark limb of the moon reaches the star, causing the latter to disappear instantaneously, even though it is at ill at same distance from the bright edge of the moon. Tha star reappears on the bright or lower limb a little over an bnur later. This occultation is well worth watching as it is the best example we shall have all the year. On the 23rd, the night on which the moon is full, it will ba cloie to Jupiter. On the 26th it will fotm a triangle with the two priuciple stars in Aries the Ram. MERCURY.

Ibis month we shall have an opportunity pur excellence of obssiving Mercury. It is visible in Virgo as an evening star for the last two weeks of the month attaining its maximum brilliancy a few days before the end. It reaches its greatest tloigation fiom the sun—twenty-six decrees - on the 28th, Lut sets about the seme s mount-two hours-later than the sun each night. It sets considerably—roughly, fifteen degrees—to the south of west. On the 21st and 22nd it is very close to Spica in tbe Virgin; the first evening it is below the star, and un ths second it is above. This appaarance of Mercury is the most favourable that we shall have for many months. VENUS, being in superior conjunction with the sun on the 13th, will not be visible this month.

MARS, in Gemini, is still an earl; morning star. It iieeß tnirty degic.s to tjhe north of east at a qua ter pi.s. Uiifee at the beginning of the mob to, and at half past two at the end. Ad early riser on the 21th will see it a little over a degree to the north of Saturn. Towards the end of the month it is close to Pollux, one of t'ae Twins. JUPITER

is now the most prominent feature of tbe evening sky, being twice as bright as Siriue, the biightest fixed star. It is at present describing a retrograde path in Pieces, and will be in opposition t.< tbe sun on tba 17th. At tbe beginning of the month it may be seen after 7 p.m , and by the end after 5.40 p.m. It risei approxmately five digress south of cast. For several munth3 row we sh. II have good opportunities it obseivirg this planet. It will be interesting to watih it creep across the sky until, by the beginning of next year, it will 02 an evening star in tbe west. Viewed thruugh a telescope, Junior is seen to possess a slightly illiptical shape. The ptlar diameter is six per cent shorter than th<3 cquitoiial; yet forty Jupiters could bs pi iced in a line across tbe moon. The telescope also reveals a series of dark belts parallel to the placet's equator. The satellites al o show interesting phenomena. Three of the blight oneß and often the fourth are eclipsed by Jupiter's shadow every revolution, and disappear for a while. When a satellite transits or passes in front uf Jupiter its shadow may be seen as a email dark spot travelling across the face of t v :e planet. All four moans are occulted every revolution, i.e., they pass behind Jupiter. These sat llites have been u c ed in a very wonderful way to determine the velocity of ligbt, for we see tbeir eclipses earlier or Uter according to our nearaess to Jupiter. When the sun, Jupiter and the earth are in a line, the sun being between the two planets, it is found that light trnin Jupihr takes sixteen minutes longer to reach the earth than when the earth ii directly between the sue and Jupiter. That is to say light travels twica 93,000,000 miles in sixteen minutes rr about 186,000 miles per second. Think of it! Seven and a half times round the equator in one second. SATUKN i 3 still a morning star in Gemini between the etars Zeta and DUta Geminorum, wbere it remans for s.veral months. It rises twer.tyeight degrees north of east at half past thr.e at present, and two hours eariier at the end of the month. NEPIUNE. The 23rd is the sixty-ninth anniversary ?f the discovery of Neptune, of which 1 will say more at some futrue date. THE FIXED STARS.

Arcturus and Spica have now moved further to tha west, and by the end of the mouth will have disappeared. Vega is the gem of the northern sky, while Altair hovers above and to the east of it. The Scorpion is now in the weer, after sunset, while the Cross is in the sjuth-west, and Achernar ii rising high in the south-east. In the east we may see the conatellatijn of Aquarius. It is easily remembered by a little gr .up of four fourth magnitude stars in the form of an equilateral triangle, with one in tbe centre, lo find this let us first turn our eyes to Fomalhaut, a bright star in Piscis Australia which is fiiph up in the east at ' nine o'clock and in the zenith at midnight. From here draw a line to Jupiter, thirty degrees away, then turn through almost a right angle t> the north-west ai.d continue for two-thirds uf tbe oiigioal distance, This leads to the little triangle, below which again is the well known square of Pegasjs. The latter consists of fuur ttiiid magnitude stars, Alpha, Beta and Gamma Pegasi, and Alpha Andromedae, each side if the square being in length about three times the distance between the two tointera to the Cro:s. One star will be found at ths apex of an equilateral triangle, tbe base of which is tbe lire from Jupiter to tbe mangle in Aquarius. Another may be placed by contiauing the line from Fumalhaut to Jupiter through two-thirds uf its own length. Having found two point] the others are easily found by completing the equate. The zodiacal constellation of Pisces, which extends below and to the right of Jupiter does not contain any bright stars of interest. The constellation of Aries—the Ram—rises about nine o'clock some thirty degrees to the north of east, It consists of three stars of tbe second, ttir.l and fourth magnitude respectively, marking out an obtuse angle, facing upwards, of 135 degrees. The third magnitude star is at tbe vertex ot the angl;, and the arm containing the brighter star—Alpha Arietis, or Hamal as it is sometimes called—ia four degrees long, while the other arm is only half this length. Tbe fainter star was the first star to be discovered double by telescopic aid. Hooke, in 1664, was the discoverer. i

Following is a table of stellar phenomena for the first ot this month. The times given must be diminished by four minutes for each day after the Ist, and it should be borne in mind, if a magnetic compass h used for rinding bearings, that it points fifteen degrees east of north. It is hoped that this table will prove useful in locating and identifying stars. The angles given represent either the altitude of the star, or its angular distance from the true ea:t or west when rising or sitting:--

p.m. An tares North 5.38 79deg. Canopus South 7.34 Odeg. Spica Weßt 7.36 18deg. Vega North 7.47 14deg. Arcturus Sets 8.15 W 25den. N Altair North 9.0 44deg. Spica Sets 9.0 W I3deg. S Fomalhaut East 9.25 56deg. Bgta Argus South 10.25 17deg. Vtga Sets J 1.10 W 52deg.N Kigel Rises 12,0 ElOdeg.S Fomalhaut North 12.5 83deg. Alpha Fegasi North 12.13 39deg.

Alcyone Rises 12.20 E 31deg.N Alu'ebaran. Rises 12 40 E 21deg.N is oue of the bright stars ia Orion; Alcyone is the central star of t:e Pleiades; AlJebaran is a roil star in Taurus, the Bull.

p.m. September 23rd 5.39 2 depress September 24tb 6.41 10 degrees September 25th 7.44 18 degrees September 26th 8.46 24 degrees Sspt.mber 27th 9.49 29 dtRrejs September 28th 10.49 33 degrees September 29th il.46 25 degrees September 30th 12 37 33 degrees PATH OF THE MOON.