Sky notes by Neil Bone 2004 August & September

seeing fine telescopic detail. Many will be Sun and Moon The planets keen to compare the Earth-based view with those being returned from the Cassini space- During August, observers in the British Mercury is poorly-placed in the evening craft that is now in orbit around the planet. Isles will find the nights lengthening con- sky east of the Sun in early August. Reach- For up to date information and images from siderably. Indeed, for those in the far north, ing inferior conjunction between Earth and Cassini, see http://saturn.jpl.nasa.gov/ the return of truly dark night-time skies Sun on August 23, the planet then pulls out home/index.cfm. from the second week of the month will be into the morning sky, reaching greatest elon- The outer gas/ice giants Uranus and Nep- particularly welcome astronomically after gation 18° west of the Sun on September 9. tune are well-placed in this interval and can summer’s permanent twilight. The Sun is Around this time, the magnitude 0 inner- be seen in binoculars. Uranus, at mag +5.7, now heading rapidly southwards along the most planet will be rising about 90 minutes is the brighter and is at opposition (180° ecliptic, and will sit astride the celestial ahead of the Sun and may be seen by keen- from the Sun in Earth’s sky) on August 27, equator at 16h 30 Universal Time (UT= eyed observers in the pre-dawn skies against just north of 5th-magnitude Rho Aquarii. GMT; BST minus 1 hour) on September the stars of Leo. Further west, in the near vicinity of mag +4 22, the moment of the northern hemisphere The morning sky at this time is domi- Theta Capricorni, Neptune is at opposition autumn equinox. By common definition, nated by brilliant mag −4 Venus, reaching on August 6 and is a more testing mag +7.8. autumn begins on the equinox, but the its greatest elongation 46° west of the Sun Being rather distant, neither of these planets nights will already have taken on a less on August 17. Venus will then be rising shows more than a small (3 arcseconds) disk summery feel by then and perhaps astrono- around 01h UT, over three hours ahead of telescopically. mers would take more the meteorological the Sun. Telescopically the planet should approach and regard the season as starting show a half-phase at this time, gradually as September opens. becoming more gibbous (similar in appear- Sunspot cycle 23 continues to produce ance to the Moon between full and last quar- occasional substantial active areas, which can ter) as early autumn advances. As its phase Minor planets be viewed safely by projecting the solar disk increases, Venus’ apparent diameter de- onto white card through a small telescope. creases below 20 arcseconds: the planet is The decline towards sunspot minimum − a pulling away from us around its inner, more The brightest of the asteroids, (4) Vesta, is few years off yet − has been erratic, punctu- rapid orbit. Venus will be presented against at opposition during September, and can be ated by interludes when the disk has been the stars of Gemini in August, slowly mov- found with binoculars looping against the quite active, although observers have also ing into Cancer in September, and will con- star background in eastern Aquarius, south begun to record days when spot groups have tinue to rise more than three hours ahead of of the Circlet of Pisces. A chart showing been completely absent. the Sun throughout this interval. Vesta’s path and suitable comparison stars The Moon is New on August 16 (good Mars, long almost lost in the solar glare, for making nightly magnitude estimates can news for meteor observers!) and September finally arrives at conjunction on the Sun’s be found at http://www.britastro.org/arps/ 14, placing the darkest night-time skies in far side on September 15 and will emerge 04-0409.jpg this interval into the middle fortnight of the only slowly into the morning sky much later Observations will be welcomed by Andy month. Full Moon falls on July 31, August in the year. Jupiter is also lost from view in Hollis, Director of the Asteroids and Remote 30 and September 28. The early-autumn this interval, reaching conjunction on Sep- Planets Section. Around opposition, Vesta waning gibbous Moon in the days following tember 22. should be close to 6th magnitude. Full rises early, giving bright evenings. In early Saturn is a morning object against the stars September, moonrise comes well before mid- of Gemini, rising around midnight UT by night UT even up to the 8th of the month, mid-September. At mag 0, the planet is by which time the Moon is a broad crescent, brighter than any of the stars in its vicinity, past last quarter. and any telescope with 50mm or more aper- Comet 2002Q4 At this time of year, retardation − the night ture and a magnification of ×40 upwards will (NEAT) to night difference between successive reveal its magnificent ring system. With Sat- moonrises − is at a minimum, thanks to the urn now beginning to head south along the shallow angle between the ecliptic and the ecliptic, the rings’ presentation is slightly Having put in a respectable, faintly naked- eastern evening horizon: although the Moon’s less wide-open than in the past couple of eye showing in May’s evening sky, Comet orbital motion carries it eastwards by about years, but we still have a good view of their 2002 Q4 (NEAT) is now circumpolar for 13° per day, it will rise only a few tens of southern side. Observers with large tel- northern observers, moving slowly east- minutes later, a bit further over to the north- escopes may be able to make out some of wards north of the Plough, and gradually fad- east, from one night to the next. (By con- the subtle banding of the planet’s cloud fea- ing. In early August, the comet may still be a trast, in spring when the ecliptic is steeply tures, especially in the latter part of the night reasonable binocular target around 7th mag- inclined to the eastern horizon the waning in September when Saturn is high in the south- nitude, though it will at this time be quite Moon rapidly departs the evening sky). eastern sky: seeing, the steadiness (rather low in the twilit northern sky. By late Sep- Autumn’s early-rising waning Moon offers than transparency) of the atmosphere, has tember, it will have faded further, but could the chance to view lunar features under their usually settled to its best by the early hours still be in range for small telescopes around sunset illumination at more sociable hours once the ground has given up accumulated magnitude +9, and best seen in the early hours of the night. daytime heat, affording the best chance of as it starts to climb in the northeastern sky.

230 J. Br. Astron. Assoc. 114, 4, 2004 Sky notes

be close to the limit of naked Meteors eye visibility between mag +5 to +6 by the time it is more The more active part of the year is here at readily accessible in early au- last, and after losing most of the really ac- tumn. Binocular and small tel- tive showers to moonlight in 2003, meteor escope users will have the observers will be looking forward to a pro- chance to follow Mira all the ductive spell starting in early August with way down to its 9th-magni- the Perseids. The Moon will initially be tude minimum early next year. slow to get out of the way, and observa- The naked-eye eclipsing tions during the first week of August will binary Algol (Beta Persei) has still be somewhat restricted by its glare. favourably-timed minima on From about August 9 onwards, however, the nights of August 30−31 the available dark sky period increases as and September 2 and 22. the Moon wanes, and by this time the During the primary, deep The Eagle Nebula, M16. CCD image by Gordon Rogers. Perseids will be starting their rise towards eclipse, Algol fades from mag. maximum on August 12. Best rates are ex- +2.1 to +3.4, a very notice- pected late on August 11−12 and early on able dip. The fade and recovery each take By September, the window is closing on August 12−13, with good activity any- about five hours. these summer delights for another year, and where from Aug 8−9 to 15−16. The Perseid the view in late evening turns towards the radiant, close to the ‘Sword Handle’ at emptier spaces of Pegasus and the other au- Perseus’ northern end, is low in the north- tumn constellations. Trailing behind Pegasus, east in early evening, climbing high in the and well up in the eastern sky by late on a early morning hours. Reports of watches Deep sky mid-September evening, Andromeda is best made by the standard methods described known to most observers for the Great Gal- on the pages at http://www.britastro.com/ As we move into August, the summer Milky axy M31: a couple of degrees from 4th-mag- meteor (and also in the article on page 220) Way in Sagittarius remains a major attraction nitude Nu And, in the more northerly (upper- will be welcomed by the Meteor Section. in early evening. The region to the northwest most from the UK) chain of stars trailing east Further details of this year’s shower can be of the ‘Teapot’ asterism made up by Sagitta- from the corner of the Square of Pegasus found on page 181 of this Journal. rius’ main bright stars, stretching up towards marked by mag +2 Alpha Andromedae. Following the Perseids, patient observers the bulge of the Scutum Star Cloud south of The end star of Andromeda’s more south- may note some activity from the Kappa Aquila, abounds with bright, well-known ob- erly chain is well worth examination in a me- Cygnids around August 20. This shower jects. A binocular sweep northwards from the dium-sized telescope (70−80mm aperture). produces low rates (around 5 meteors/hr at Teapot’s spout will trawl up, in quick succes- This is Gamma Andromedae (Almach), one best), but is noted for its occasional very sion, the Lagoon Nebula (M8), Trifid Nebula of the finest colour-contrast double stars in bright meteors. (M20), Swan Nebula (M17) and Eagle Nebula the sky. The primary is a mag +2.3 orange Through August and September, sporadic (M16), each readily visible in a pair of 10×50s star, with the green mag +4.8 secondary just rates are at their best for the year, and a on a clear, moonless night. under 10 arcsecs away − an easy split at ×50. experienced watcher might log up to a dozen Another fine early-autumn double is meteors per hour even on ‘non-shower’ nights Gamma Arietis (Mesarthim). I find this at- from a clear, dark location. This background tractive not for any pronounced colour (both is augmented by minor shower activity from stars are white), but for the close match in the Piscids through September and October. brightness of the two components (mag +4.6 Part of the year-round ‘drizzle’ of low-level and +4.7), which are separated by a little activity from close to the ecliptic plane, the less than 8 arcseconds and are aligned ex- Piscids produce perhaps a couple of slow, actly north−south. modestly-bright meteors per hour from a The autumn sky has one or two good open diffuse radiant east of the Circlet of Pisces. star clusters. One of the best for small tel- escopes and binoculars (indeed, it becomes rather scattered and unimpressive in large instruments) is M34 (NGC 1039), midway between Algol and Gamma Andromedae. Variable stars This is a loose collection of about 40 stars between mag +6 and +8 in an area 35 arc- minutes across, somewhat more than the The long period (Mira-type) variable Chi Moon’s apparent diameter. Under good con- Cygni had a bright maximum, almost reach- ditions, M34 is visible to the naked eye. Its ing magnitude +4, in late May, and could overall catalogue magnitude is +5.2. remain within binocular range well into Au- By late evening in September, the best- gust. Characteristically, the fade from maxi- known of all star clusters − the Pleiades in mum is slower than the preceding rise. Chi is Taurus − is well up in the northeastern sky, located close to Eta Cyg on the Swan’s neck. a indicator that autumn is truly under way The prototype of the class, meanwhile, with the promise of long, dark observing emerges into the early morning sky during nights ahead. August following solar conjunction. Mira Summer delight: the Lagoon nebula, M8, (Omicron Ceti) should have been at maximum photographed from La Palma by Nik Neil Bone towards the end of May, and will probably Szymanek.

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