Sky Notes: 2013 August & September by Brian Mills − (Written for 22:00 UT on 2013 September 1.) the other members of the Summer Triangle evening position of the ecliptic is the cause of Altair in Aquila, which is always easy to iden- our problems from the UK at this time of year, In the north Ursa Major has almost completed tify because of the two stars (β and γ Aquilae) being at most 15° high. This means that it makes its descent towards the horizon meaning that on that attend it on either side. a very shallow angle with the horizon, not helped the opposite side of the pole, Cassiopeia is climb- Lower, but still on the meridian, is Capricornus by the fact that Mercury is almost 3° below the ing and Cepheus is approaching culmination not which contains the globular cluster M30, visible ecliptic when the next elongation occurs in the far from the zenith. There are a number of open in larger binoculars although a moder- clusters that fall within the borders of Cepheus, ate sized telescope is needed to begin the brightest being NGC 7160 which lies inside resolving individual stars. Lower still the quadrilateral that makes up the main body of lies the small and insignificant the constellation. At magnitude 6.1 it requires Microscopium. On a really clear only a small telescope or binoculars. Cassiopeia evening it is worth trying to locate its also has its share of such clusters, the best known brightest stars; gamma (γ) at magnitude of which are M52 (magnitude 6.9) and NGC457 4.67 and epsilon (ε) at 4.71 despite their (magnitude 6.4). being at an altitude of just over 6°. Now is a good time to identify the convoluted Turning to the west, the final mem- shape of Draco the dragon, which begins with its ber of the Summer Triangle, brilliant tail between the two Bears and ends with its head Vega in Lyra, is at a commanding alti- close to Hercules. The third star in the tail of the tude of 65°. Beta (β) Lyrae is a much dragon is Thuban, otherwise known as Alpha observed naked eye variable with a pe- Draconis although it is not the brightest star in riod of thirteen days and a magnitude the constellation. Nearly 5,000 years ago it had range from 3.3 to 4.3. Also in Lyra is the distinction of being the Pole Star, but due to the lovely planetary nebula M57 at the Earth’s precession it has lost that role, one magnitude 8.8 lying roughly on a line that it will not return to until approximately 20350 between beta (β) and gamma (γ) Lyrae AD. The brilliant Capella is now visible some 15° and slightly closer to the former. An above the north eastern horizon. aperture of 120mm will show it well Looking east we see that the autumn favour- but the central star at magnitude 14.8 The Ring Nebula M57 taken using a 250mm SCT and Starlight ites of Pegasus, Andromeda and Perseus are will require something with consider- Xpress MX718. Imaged by E. J. Mills from La Palma. Lower left making their presence felt. The asterism that we ably more light gathering power such can be seen the mag 14.4 spiral galaxy IC 1296. know as the ‘Square of Pegasus’ is of course as a 300/350mm instrument. something of a misnomer because the top left Below Lyra and skimming the south western second week of October. However, providing star is Alpheratz or Alpha Andromedae. Pegasus horizon are the two indistinct constellations of caution is exercised, Mercury can be found in is home to M15, a globular cluster that lies on Serpens and Ophiuchus, both of which were daylight with Goto telescopes of moderate size the constellation’s western fringes close to the members of Ptolemy’s original 48. The former although ‘sweeping’ for the planet this near the border with Equuleus. At magnitude 6.3 it is an has been divided into two (Serpens Caput and Sun should most certainly not be employed. easy object in binoculars but to resolve indi- Serpens Cauda) by the large and faint Serpent- Venus suffers from the same problem in that vidual stars requires a telescope aperture of at Bearer. M5 is a magnitude 5.7 globular cluster in it will always be close to the horizon. It begins least 120mm. Below Pegasus we find one of the Caput which should be just visible to the naked August 32° from the Sun but setting just 1¼ fishes of Pisces, a constellation that has been, eye given a dark site and good air quality. It is an hours after it. With the Sun 6° below the hori- and will continue until 2017 to be, the home of excellent sight in a moderate telescope and is zon (the start of nautical twilight) Venus is just the planet Uranus. It contains a smattering of well worth observing despite its low altitude. over 4° above it, so despite having a magnitude galaxies, the brightest of which is the face-on At this time of the year the Milky Way is a of −3.8 will be an extremely difficult object. If spiral M74 at magnitude 9.2, although its sur- beautiful sight as it makes its way through we fast forward to the last day of September we face brightness will be lower. It is best located Perseus, Cassiopeia, and Cygnus before it me- can see what changes there have been. The angu- by star hopping from eta Piscium which lies 1° anders to the horizon via Aquila and Sagittarius. lar separation of the two bodies is now over 44°, 20' away to the west. At the time of Perseid maximum, meteor watch- but Venus still sets around 1¼ hours after the Towards the south the bright star Deneb lies ers at dark sites will be able to admire its maj- Sun and is still approximately the same height on the meridian at an altitude of more than 80° esty particularly at times of good transparency. above the horizon when nautical twilight begins. meaning that the Pelican and North American A pair of binoculars should always be to hand to Things do, however, improve as the year wears nebulae are well positioned for imaging. Below sweep it looking for those jewels that a simple on and although the angular distance between and slightly to the west of Deneb we find one of pair of 7×50s can so often reveal. Venus and the Sun decreases, the planet’s height above the horizon starts to increase. Earth reaches the Autumnal Equinox on Sep- tember 22 at 20:44 UT when its axis is tilted Planets and dwarf neither towards nor away from the Sun. planets Phases of the Moon: Mercury reached greatest western elon- 2013 August/September gation on the last day of July, but de- spite this is poorly placed for observa- New First Full Last tion during August. Superior conjunction quarter quarter occurs on August 24 but the situation doesn’t improve during September with Aug 6 Aug 14 Aug 21 Aug 28 the planet setting only 30 minutes after Sep 5 Sep 12 Sep 19 Sep 27 Open clusters in Cepheus and Cassiopeia. the Sun at month’s end. The early 236 J. Br. Astron. Assoc. 123, 4, 2013 Sky notes Mars is becoming a more obvious morning object whose brightness remains steady at Lunar occultations of bright stars +1.6 whilst its apparent size increases slightly. It begins the period in Gemini (in the com- Date Time Star Mag Ph Alt ° % illum. m m pany of Mercury and Jupiter) although its Aug 1 09.15 epsilon Tauri 3.5 DB 54 26 140 direct motion carries it into neighbouring Can- Aug 1 10.28 epsilon Tauri 3.5 RD 45 25 70 cer before the month’s end, finding itself Aug 15 20.41 ZC 2394 6.3 DD 15 66 60 amongst the stars of M44, the Beehive clus- Aug 17 21.12 ZC 2724 6.3 DD 19 86 70 ter, on September 9. By the end of September Aug 17 22.49 SAO 161842 6.9 DD 16 86 110 it has made its way across the border and into Aug 17 23.26 ZC 2733 6.8 DD 13 86 110 Aug 18 20.54 ZC 2889 6.9 DD 20 93 110 Leo. At the start of August Mars rises 2½ Aug 19 23.41 ZC3051 6.8 DD 25 98 110 hours ahead of the Sun whilst by the end of Aug 27 00.09 ZC 450 6.4 RD 26 63 60 September this has become nearly 4½ hours Aug 29 00.04 ZC 718 6.0 RD 13 44 40 although it will be next January before it be- Sept 8 13.56 alpha Virginis 1.0 DD 27 11 40 comes an evening object. Sept 8 15.08 alpha Virginis 1.0 RB 26 11 60 Jupiter is a morning object that remains in Sept 11 20.01 Psi Ophiuchi 4.5 DD 8 40 40 Gemini throughout August and September. Its Sept 12 18.49 SAO 185318 7.0 DD 17 51 70 magnitude increases slightly from −1.9 to − Sept 14 18.16 ZC 2828 5.8 DD 18 73 110 2.1 during the period with this brightening con- tinuing for the rest of the year. At the begin- come morning objects in Leo, rising more than ers that are either of fainter stars or those ning of August the planet rises more than 2½ two hours ahead of the Sun as the period ends.