Now a few notes defining terms which may be encountered in the text to follow:

Transcription

1 The times, circumstances and star charts to follow are configured for the Melbourne Observatory in line with other publications of the Astronomical Society of Victoria (ASV), for which these viewing notes are principally compiled: Longitude ' 23.8" E, Latitude 37 49' 54.1" S [" denotes arc second = 1/60 th of an arc minute (symbol ') or 1/3600 th of a degree (symbol )]. The notes contain many references to rise and set times, all configured for the co-ordinates given above; the following procedure will facilitate determining the correct times for other locations. The adjustment required for longitude is straight forward for each degree east (of Melbourne Observatory) subtract four minutes; conversely, add four minutes for each degree west. Adjustment for a difference in latitude is dependent on the declination of the object concerned how far north or south of the celestial equator it lies. The table below, from the yearbook of the ASV, gives the required adjustment (in minutes) for any object at a declination of between +30 and -30 (by convention, north is positive and south negative) when viewing from any location between latitudes -28 and -44 ; interpolate for intermediate latitudes/declinations. Note: add these values to times of rising and subtract from setting times. Whereas the declinations of stars and other deep sky objects are (very nearly) constant, those of the Sun, Moon and planets change considerably over time; a suitable resource for determining declinations is therefore required to obtain the adjustment for difference in latitude as described above.

2 While the reader may have ready access to such resources, I offer the following suggestions for those who do not: the ASV yearbook, free to members and available at reasonable cost to others (Sun and planets only), the yearly publication Astronomy Australia (Sun, planets and Moon), and various astronomical software packages (typically catering for all celestial objects). Other sources may be available on-line. Note that some resources give co-ordinates for epoch denoted as J 2000 whereas others may quote real time figures, denoted J Now. The discrepancy between the two systems will not be significant for the purpose at hand. Now a few notes defining terms which may be encountered in the text to follow: For those not familiar with the terminology used to describe phases of the Moon, note that it is referred to as waning (hard a ) when the phase is decreasing daily and waxing (soft a ) when increasing, and as a crescent when less than half lit and gibbous when more than half. Thus you may find it referred to in the text as, for example, a waxing crescent Moon. Appearances of the abbreviation au in the text denote astronomical unit, the average Earth-Sun distance, currently defined as 149,597, km; sm denotes solar mass, the mass of our Sun. The abbreviation ZHR, where it appears in relation to meteor showers, refers to the zenith hourly rate, the number of meteors per hour which can be expected to be seen under ideal conditions, with the radiant (the point from which the meteors appear to emanate) at the zenith and a clear dark sky. The ecliptic, shown as a green line on many of the star charts to follow, is the path followed by the Sun and (very nearly) the planets as they arc across our sky daily. As the outer planets, those that orbit farther from the Sun than does Earth, move along their orbital paths, they move from west to east in our sky relative to the stars; this is referred to as direct or prograde motion. Around the time of opposition however, when we overtake them on our inner, faster orbital path, they change direction, moving east to west relative to the stars. Referred to as retrograde motion, this phenomenon is caused by the same effect as that seen when a car which is overtaken seems momentarily to move backwards in relation to a line of trees in the background. On any given night, a planet is said to be transiting (or culminating, there is a subtle difference between the two) when it reaches its highest point above the horizon in its passage across our sky that evening do not confuse this use of the term transit with the same word often used in these viewing notes to describe the passage of the moons of Jupiter across the face of their parent. Regarding the inner planets, Mercury and Venus, which never stray very far from the Sun in our sky, greatest eastern elongation refers to their maximum angular distance east of the Sun when they are visible in our evening skies; similarly, greatest western elongation refers to their maximum angular separation west of the Sun when visible in our morning skies. They are said to be in inferior conjunction when passing between Earth and the Sun on their inner orbital tracks, and in superior conjunction when rounding the far side of the Sun from our perspective. As a handy (excuse the pun) guide to estimating the angular separation of two objects, one finger held at arm s length typically spans a little over 1, a closed fist 10 and an open hand, thumb tip to tip of little finger, 20. The symbol " denotes arc second = 1/60 th of an arc minute (symbol ') or 1/3600 th of a degree (symbol ). The notes to follow adopt the practise of quoting the span of planetary disks to the nearest arc second if that is sufficient to distinguish the values throughout the month in question and identify trends; one, two

3 or occasionally three decimal places may be given if it is necessary to do so in order to achieve these stated ends. The same approach is employed in relation to the phase of planetary disks, denoting their degree of illumination, and the inclination of Saturn s ring system. All references to twilight in these notes relate to astronomical twilight, which ends/begins when the Sun is 18 below the horizon. Stars are generally referred to by their common names, if they have one, with their Bayer designations appended; Flamsteed numbers are often used for lesser stars, with HIP, TYC & USNO designations used to identify progressively fainter stars. Note finally that perihelion or aphelion of Mercury, Venus and other planets refer to the physical separation in space of the planet in question and the Sun, and are unrelated to their angular separation in our sky. What s in the sky this month; May 2018: 6 th Moon at apogee (farthest from Earth, 404,457 km). 6 th /7 th Eta [η] Aquariids meteor shower peaks. 8 th Last quarter Moon. 9 th Jupiter at opposition; Eta Lyrids meteor shower peaks. 15 th New Moon. 16 th Venus at perihelion (closest to Sun, million km / au); Aldebaran (Alpha [α] Tauri) occulted by Moon (not from Australia, see below). 18 th Moon at perigee (closest to Earth, 363,776 km). 22 nd First quarter Moon. 30 th Full Moon. N.B.: When reading the following, refer back to the explanatory notes at the beginning of this article for information on terminology, angular separation approximations and adjustment of latitude & longitude. Two meteor showers peak this month, the Eta Aquariids (generated by debris from Halley s comet) and Eta Lyrids, on the 6 th and 9 th respectively; the former is hailed as the premier shower in the southern hemisphere, while the latter is a minor shower with a ZHR of just three.

4 The shower emanating from Aquarius boasts a ZHR of 40 or more; unfortunately, this year s event is heavily affected by the 62% illuminated waning gibbous Moon, which rises at 10:23 pm, leading the shower (rising in the east at 1:50 am) across the sky by a little under 40, washing out fainter specimens. Additionally, maximum activity is predicted to occur in daylight, at 5:53 pm, but this is mitigated by the broad shoulder of the peak, with high rates a day either side. The above chart is configured for 5:36 am on the 7 th, the beginning of astronomical twilight, with the radiant at an altitude of 41 in the NE. The radiant of the Eta Lyrids is also depicted; peaking on the 9 th (when it rises at 1:32 am), its radiant will sit only a degree or so west of the position shown here. The occultation of Aldebaran, by the Moon, on the 16 th, will only be visible to viewers in NW Greenland, N Canada and parts of the Arctic. Locally, closest approach of the Moon s limb to the star, just under 1⅓, occurs at 11:44 pm, with Aldebaran 60 below our northern horizon. Mercury Mercury is fully immersed in its best morning (or evening, for that matter) apparition of 2018 as May begins, having been at its greatest angular separation 27 west of the Sun on the last day of April. On May 1 st, Mercury rises at 4:45 am, more than ¾ hour before twilight commences at 5:32 am, by which time it already stands 9 above the ENE horizon (come sunrise, 7:01 am, it s at an altitude of 25 ). Telescopic views at this time are aesthetically pleasing, showing a disk short of half lit, 45%, spanning 8" and shining strongly at magnitude 0.4. With new Moon falling on Tuesday 15 th this month, we ll nominate Saturday 12 th as our viewing night. On the following morning of the 13 th, Mercury s rise time has slipped to 5:13 am; it still presents as an enticing target, however, attaining an altitude of 5 ENE before the sky begins to brighten at 5:41 am (21 at sunrise, 7:11 am). The view through a scope is not as enticing as it was on the 1 st, span and phase of the disk having reduced and increased respectively to 6" and 64%, but it shines considerably brighter, at magnitude -0.1 (the more expansive phase outweighs the reduced disk size; Mercury, with its tight orbit, is the only planet which exhibits this behaviour). The chart below is configured for 5:41 am; the 9% illuminated waning crescent Moon, only 11 away, enhances the scene without illuminating the morning sky greatly. The Great Square of Pegasus hovers above the horizon to the left (west).

5 Mercury passes close to a couple of galaxies this month. Low to the horizon, each will be a challenging telescopic object; the following information is presented for those who wish to give them a try. In the predawn sky of the 7 th, the face-on spiral NGC 488 sits a little over ½ to the lower right (east) of Mercury; at magnitude 10.3 and spanning some 5' x 3', it will be at an altitude of just 7 at the beginning of morning twilight, 5:36 am. An even greater challenge awaits those who attempt to spot the elliptical galaxy NGC 821 on the 16 th, when it may be found (good luck ) just under ¾ to the lower left (ENE) of Mercury; at around magnitude 11 and spanning 2.4' x 1.7', it s a mere 2⅔ high as twilight begins to invade the sky at 5:43 am. Note that the spans given here relate to the extremes of the galaxies, your scope will show considerably smaller bodies. Rising after twilight begins from the 21 st onwards, Mercury s descent back towards the morning horizon subsequently gathers pace. By month s end, it doesn t rise until 6:49am, and is just 6 high at sunrise, 7:26 am; the disk is almost fully illuminated, 96%, spans 5", and is lost in twilight despite shining vigorously at magnitude The Messenger of the Gods darts through the constellations during May. Crossing the border from Cetus into Pisces on the 1st, it revisits Cetus from shortly before midnight of the 15 th /16 th until just before 3:30 pm on the 16 th, when it crosses into Aries, subsequently moving into Taurus on the 27 th. Venus After a very slow climb away from the evening horizon for almost the entire year (having begun to do so after January s first week), Venus picks up the pace this month, setting after evening twilight is extinguished from the 6 th onwards. On the 1 st, it is at an altitude of 13 at sundown, 5:33 pm, the planet itself setting at 6:56 pm; spanning 11.6", Venus disk displays a phase of 88% and punches through the twilight with ease, blazing at magnitude Come our viewing night of the 12 th, Venus is at an altitude of 15 at sunset, 5:22 pm, 1½ clear of the WNW horizon as the sky fully darkens at 6:52 pm, and sets at 7:03 pm; its span is out to 12.0", 86% illuminated, and it shines incrementally brighter still, magnitude No chart is needed to locate it; after the Sun sets, wait ½ hour or so and scan the NW sky at an altitude of 11 (roughly a fist at arm s length) and you ll soon spot it shining through the twilight. After having done so for the first time, an interesting exercise is to attempt a sighting five or ten minutes earlier the next evening, continuing to shave the viewing time in subsequent days to explore the limit of your visual acuity. At the end of the month, Venus is 19 clear of the horizon as the Sun sets at 5:10 pm, 7 as twilight expires (6:43 pm), and doesn t sink below the skyline until 7:27 pm; span, phase and visual magnitude stand at 13.0", 80% and Venus transitions from Taurus into Gemini on the 20 th, remaining in that constellation for the remainder of the month. Mars Mars is moving to centre stage in more ways than one, parading high in the sky in the early hours of the morning, and nightly growing larger and brighter in our skies as the apparition destined to be its best in 15 years picks up pace, heading towards opposition in late July. As the month of May begins, the Red Planet is rising at 10:09 pm, its 11" disk (in excess of the 10" generally regarded as the threshold above which surface detail is able to be discerned on Mars) displaying a phase of 88% and shining strongly at magnitude -0.4.

6 By the time our viewing night of the 12 th arrives, there is further noticeable improvement as we catch up to Mars on our inner, faster orbital track. Now rising in the ESE at 9:46 pm, Mars shines at magnitude -0.7, on a par with Canopus (Alpha Carinae), the second brightest star in the night sky; the span of the disk has increased to 12", 89% illuminated. The chart to follow shows the scene at 1:00 am on the morning of the 13 th, with Mars having ascended to a respectable 36 above the eastern horizon; the trio of Jupiter, Saturn and Mars stand out against the starry background (Pluto s position is indicated for later reference). As you examine Mars telescopically, drop down ¾ to view the globular cluster M75; on the following morning, that reduces to 24', and on the morning of the 15 th, planet and globular stand side by side only 19' less than ⅓ apart. By month s end, the rate at which Mars (which rises at 9:05 pm) continues to grow both in terms of size and visual magnitude are on stark display, albeit compromised by the presence of the near full Moon in the sky. The disk spans 15" and shines at magnitude -1.2, approaching the brilliance of Sirius (Alpha Canis Majoris), the brightest of all stars in the night sky; Mars is destined to outshine that luminary in the second week of next month, before going on to outstrip even mighty Jupiter. Mars crosses the border from Sagittarius into Capricornus, where it sees out the month, on the 15 th. Jupiter The King of the Planets reaches opposition on the 9 th, rising at sunset and at its biggest and brightest for this apparition, but its wide, slow orbit dictates that the view is optimal throughout the month of May and beyond. Rising at 5:57 pm on the 1 st, it is already at an altitude of 12 by the time evening twilight expires at 7:02 pm; the disk of the giant planet spans 44.7" and shines at magnitude

7 Our viewing night falls just three days after opposition, affording pristine views if the planet is allowed to rise above the mire found close to the horizon. After cresting the ESE horizon at 5:09 pm, Jupiter is 2 high at sunset, 5:22 pm, and 19 at the close of twilight, 6:52 pm; span and visual magnitude are 44.8" and The below chart is configured for 10:45 pm on the 12 th ; the time has been chosen to allow you to witness Io passing behind (being eclipsed by) Jupiter, disappearing over the period 10:55 pm 10:58 pm (note that no wide field chart is necessary to locate the planet, just look for the brightest star by far, 62 high in the NE). If you revisit the planet later on, you can witness Io reappear to Jupiter s upper right (east) between 1:11 am and 1:14 am it will magically do so about 2' from the planet, having actually re-emerged into Jupiter s shadow between 1:04 am and 1:07 am. The other three Galilean moons are also moving in towards their parent (from the east); from left to right on the chart, the moons shine at magnitudes 5.2, 5.5, 5.8 & 4.8. No stars in the area shine brighter than 10 th magnitude, most far dimmer; as such none are plotted. On the 31 st Jupiter is 15 high at sunset, 5:10 pm, and 34 high as twilight ends at 6:43 pm; its disk then spans 44.1", shining at mag The King remains in the constellation of Libra until after mid-november. Saturn Due to reach opposition late next month, Saturn is growing larger and brighter in our sky; with the rings still inclined at an angle in excess of 25 (after maxing out at almost 27 last October), it s a must for viewing through any sized scope. As May begins, the Ringed Wonder rises at 9:04 pm; its disk spans 17.5", the rings 39.7" at an inclination of 25.50, together disk and rings shine at magnitude 0.34.

8 On our viewing night of the 12 th, Saturn breaches the ESE horizon at 8:20 pm. Disk and rings span 17.8" & 40.3" respectively, the latter inclined towards Earth at ; overall visual magnitude is Note that while the tilt of the rings is decreasing in the longer term, it increases a little from late April until late September due to our changing viewing perspective as we overtake Saturn around the period of opposition. The chart in the notes on Mars shows where Saturn sits in relation to that planet, as well as Jupiter, Antares (the luminary of the prominent constellation figure of Scorpius) and the Teapot asterism of Sagittarius; once you ve spotted it, turn your scope on it in consultation with the following magnification, configured for the earlier time of 11:15 pm, with Saturn at an altitude of 32 in the eastern sky. The visual magnitudes of Saturn s seven brightest moons, as shown, are as follows: Mimas 13.2, Tethys 10.5, Enceladus 12.0, Dione 10.7, Rhea 10.0, Titan 8.6 and Iapetus Any scope will show Titan, a six incher will pick up Rhea, Tethys and Dione, Enceladus and Iapetus may call for an eight incher and faint Mimas a ten inch or larger. Stars dimmer than magnitude 14.0 have been omitted from the plot. Whereas the software automatically depicts brighter stars as commensurately larger than dimmer stars, it unfortunately plots all the moons except Mimas at the same size, irrespective of their brightness. As Iapetus is the only moon which has nearby stars of comparable brightness, the size of its marker has been manually set to accurately reflect its brightness in relation to the stars thus, at magnitude 11.5, it is shown as marginally smaller than the star of magnitude (TYC ). Identification of Tethys, Enceladus, Dione, Rhea and especially bright Titan should be straight forward, through an appropriate instrument, due to the lack of stars which may be mistaken for them (the star below Rhea shines at mag 13.1). Even faint Mimas should present no difficulty (if your scope has enough light gathering power), as no stars near it shine brighter than mag Identify Iapetus by looking in the appropriate direction and distance using the ring plane and the other moons as a guide for the relatively bright trio of the moon and the two nearby labelled stars; note that the double star at the right of the chart, with components of magnitudes and 11.70, shines as one star of magnitude As the chart shows, there are no stars between the inner moons and the trio which rival them in brightness; all (bar one of mag 12.7, partly off the chart at bottom centre) are 13 th magnitude, as is the star to the bottom left of Iapetus (USNO J ). Note, for the sake of completeness, that the star midway between and the double shines at mag At the end of May, Saturn is rising at 7:01 pm, just a little over ¼ hour after twilight wraps up (6:43 pm); it shines a little brighter, magnitude 0.16, and the span of the disk and rings is out to 18.2" and 41.2" respectively, the rings at an inclination of

9 Saturn will spend 2018, 2019 and most of 2020 in Sagittarius. Uranus Having been in conjunction with the Sun last month, Uranus remains too close to it for decent views this month, although an interesting opportunity presents on the morning of the 14 th (see below). At the start of May, the planet rises at 6:05 am, and sits just 10 clear of the horizon at sunup, 7:01 am; its disk spans 3.38", shining at magnitude On the morning of the 13 th, following on from our viewing night of the 12 th, rise time has come forward to 5:21 am, and Uranus is at an altitude of 3½ ENE as twilight begins to challenge the darkness at 5:41 am; disk span and brightness stand at 3.39" & mag At this stage, Uranus sits just under 2½ to the lower left of Mercury (see the Mercury map), but a better view is to be had the following morning when Mercury is sandwiched between Uranus, 2¼ to its left, and the 3.6% waning crescent Moon, 2⅓ to its right, as shown below (time is 5:41 am, when twilight begins). As the month draws to a close, Uranus is rising at 4:15 am and starting to attain a little altitude in the pre-dawn sky, sitting 17 clear of the horizon at the beginning of morning twilight, 5:52 am; it s also a touch larger and brighter at 3.41" & mag Uranus is in Aries after crossing over the border from Pisces (where it had resided on and off since March 2009) last month; apart from recrossing into Pisces from early December this year until early February next year, it will remain wholly within Aries until first sampling Taurus in May Neptune A couple of months past conjunction, Neptune has now distanced itself sufficiently from the murky horizon to warrant telescopic views. Even at the beginning of the month it s at an altitude of 35 at the commencement of morning twilight, having risen at 2:32 am; shining at magnitude 7.93, its disk spans 2.24". Rising in the east at 1:46 am on the morning of the 13 th, Neptune is a generous 44 high in the NE at 5:41 am, the first sign of the impending dawn (although still almost 2½ hours short of transiting at this time); brightness and span have improved incrementally to mag 7.92 and 2.25". The wide field chart depicting the meteor radiants shows where Neptune sits at 5:36 am on the 7 th ; it provides a good approximation to the planet s position on the 13 th at 5:00 am, the recommended viewing time, with the ice giant 37 clear of the NE horizon. Note from that earlier chart Neptune s general location in relation to the Circlet asterism in Pisces and the Y of Aquarius, both of which sit above the Great Square of Pegasus, ascending in the NE. Having identified the area of concern, refer to the magnified view below (configured, as indicated above, for 5:00 am on the 13 th ).

10 The chart shows stars down to magnitude 6.0; unless you are gifted with excellent eyesight and a very dark sky, you re unlikely to see any dimmer stars with the naked eye. Begin to hone in on Neptune from the Y ; note that there is a paucity of naked eye stars between that asterism and the the stars marked with their magnitudes of 3.71 & 4.21, respectively Lambda [λ] Aquarii and Phi [φ] Aqr, the brightest such intervening star being Kappa [κ] Aqr, mag Accordingly, Lambda and Phi are easy to identify; they act to delimit the final magnification below, which will allow you to pinpoint your planetary target.

11 This chart shows stars down to magnitude 9.5, typically around the limit of a finder scope. A few of the brighter stars between Lambda and Phi are labelled (with their visual magnitudes); these are all considerably brighter than Neptune (mag 7.92), while some that are unlabelled are dimmer than the planet and others a little brighter. Neptune should be an easy capture, through your finder, by reference to 4.21 (Phi) and 6.93 (HIP114445) because, as shown by the chart, the field around it is devoid of stars bright enough to be seen. The planet may also tend to betray its identity courtesy of a steady shine relative to the twinkling stars and a subtle blue-grey hue. Note the two white crosses the one to Neptune s upper left on the chart shows where the planet sits at the start of the month, that below is for month s end. Once you ve found your quarry, confirm capture by switching to the main eyepiece at high power (the higher the better, provided the view remains crisp, I recommend at least 200x) to resolve its tiny disk. On May 31 st, Neptune is rising at 12:37 am, and reaches an altitude of 55 before the sky starts to brighten at 5:52 am; the disk spans 2.27", shining at magnitude Neptune is to be found within Aquarius until 2022/23. Pluto Due to reach opposition in July s second week, Pluto is now rising mid-evening; the fact that it is so small and faint dictates, however, that we must wait a while longer for the best viewing opportunities, high in the sky at a respectable hour. As May gets underway, Pluto is rising at 10:00 pm, its 0.096" disk (far too small to be resolved in amateur instruments) glowing gently at magnitude On the 12 th, rise time has come forward to 9:16 pm; disk span is unchanged (to the third decimal place), while visual magnitude has nominally improved to mag Wide field charts in the notes on meteors and Mars show where the tiny frozen orb sits in our sky in relation to Mars, Saturn and the Teapot asterism of Sagittarius; the magnification depicted here, configured for midnight, zooms in for a closer view. This chart shows stars down to magnitude 6.1; as such you probably won t be able to see the faintest stars plotted with the naked eye. Use Saturn and Mars to identify the broad arc of labelled naked eye stars, from top to bottom they are: Xi 2 [ξ 2 ] Sagittarii, Omicron [ο] Sag, Albaldah (Pi [π] Sag), 43 Sag, Rho 1 [ρ 1 ] Sag and Upsilon [υ] Sag. Having done so, use the arc to identify the unlabelled star just below Pluto on the chart, and that to its top left, respectively HIP95965, mag 6.1, and 50 Sag, magnitude 5.6. The former will likely be too faint to see without optical assistance, the latter may be within reach; they delimit the final chart on the following page.

12 HIP95965 and 50 Sag are labelled (with their magnitudes) at top and bottom respectively. As they are a little over 1 apart, I d suggest first choosing a low power eyepiece which has a field of view (FOV) just large enough to comfortably show both these stars, in order to relate what you see in the sky to the chart. On my scope, which has a focal length of 1500 mm, eyepieces with a focal length of 25mm-35mm, depending on the apparent FOV (marked on the eyepiece, its packaging or documentation), would suit. Choose an eyepiece for your scope using the following formula: eyepiece focal length = 1.2 x scope focal length / apparent FOV (aiming for an actual FOV of 1.2 ). Labelled, in blue, are a few stars in Pluto s general vicinity which are bright enough to show up in a finder scope for those who wish to examine the area in that manner, but as the field of view of a finder is around 4, they will be clustered quite close together better to use the main eyepiece. While this chart was not originally intended to zero in on Pluto itself (a final detailed magnification will be presented in July and the months to follow), it might do so in a pinch, as it shows stars down to magnitude 14.1, almost as faint as the planet. First note, on the chart, the two faint but easily seen stars, which shine at mag s 12.6 and 13.25, respectively just above and below the arrowhead marker for Pluto. If you then look very closely at the chart you may see two extremely faint stars, one above and the other bottom left of the arrowhead, which shine at magnitude and respectively, just a little brighter

13 than Pluto is between Pluto and 12.6, while is left of and slightly above These two pairs of stars, if you can see them all through a high power eyepiece, will lie above and below a fifth star, which is Pluto. On the last day of the month, Pluto rises at 8:00 pm, spans 0.097", and shines at magnitude 14.24; it meanders through Sagittarius until 2023/24. This month s feature is NGC 3132, the planetary nebula known as the Eight Burst Nebula or the Southern Ring Nebula, in the constellation Vela. The nebula is situated 2000 light years from Earth, and is receding from us at 49 kilometres per second (kps). Planetary nebulae, for the uninitiated, have nothing to do with planets other than the fact that they tend to appear, through small instruments, as opaque spheres, similar to planets (the term is thought to have first been used by William Herschel in the 1780 s and has stuck). Their real nature is that of an expanding shell of gas, being the outer layers of a Sun-like star being expelled at the end of its life, leaving behind only a dense core called a white dwarf (this is the fate of our Sun in about 5 billion years, don t wait up ). In the case of NGC 3132, the gas is moving away from the core at some 14 kps. As with the vast proportion of objects of interest in the night sky, the planetary is quite easy to find if the correct approach is taken (regular readers may tire of hearing this, but it s true). Refer to the following chart, which is configured for 8:00 pm on the 12 th, looking south-west; it s a good approximation of the naked eye view for those with good eyesight under dark skies. All star charts courtesy of StarryNight Pro TM Version /Simulation Curriculum Corp. Begin your search by identifying the Southern Cross (Crux, towards the upper left of the chart) and the False Cross; if you re unfamiliar with the latter, it looks, as shown, like an enlarged mirror image of the

14 Southern Cross. Look then past the False Cross, on the opposite side to Crux, for the lowest two of the five circled stars; beginning with the lower of the two, they are Suhail al Muhlif (Gamma [γ] Velorum) and Al Suhail (Lambda Vel). Shining at magnitudes 1.8 and 2.2 respectively, they stand out courtesy of their brightness and the fact a line joining them runs parallel to the long axis of the False Cross. Picturing a line from Gamma up to Lambda, extend the line by half its length while veering just a little to the right to arrive at the next circled star, Psi [ψ] Vel; at magnitude 3.6, it s a little fainter, but still very comfortably visible to the naked eye, and conspicuously brighter than stars around it. Finally, veer left ~ 30, going a distance intermediate between the first two lines, to reach the circled star, HIP50191, mag 3.8 (just marginally fainter than Psi Vel), next to the nebula. This star, which will serve as the final launching post for your assault on the nebula, is again conspicuous, only HIP50799, which you can see on the chart just above it, is anywhere near as bright, and it s a full magnitude dimmer, at mag 4.8; in all likelihood, you won t see any others in the immediate vicinity as they are mag 5.6 or dimmer. Confirm that you have arrived at the correct star by noting its position relative to the remaining circled star to its left on the chart, mag 2.7 Mu [μ] Vel, and Crux, the two stars lining up with the heart of the constellation pattern. Note that you may find it easier to identify the HIP designate directly via Crux and Mu; you say banana, I say banarna, the two approaches complement one another. Any further magnification at this stage, with the nebula under 2¼ away, would be counterproductive just fit a low power eyepiece and slowly sweep the appropriate area of sky, looking for a small but bright circular haze. I cannot detect any evidence of the figure eight which gives the nebula its common name and is said to be visible in amateur scopes. My scope shows, instead, an almost perfect circle with a well defined edge, presenting as quite bright when viewed with averted vision, the technique of looking to the side of the object of interest, thus utilising the light gathering power of the rods (as opposed to the colour sensitive cones) which are situated predominantly away from the centre of the eye s retina. Views taken at 88x, 120x, 188x and 250x, were all pleasing 188x probably most so as the nebula takes magnification well. That wraps up this edition of The Australian Night Sky, which will return next month to hunt down another planetary not too far away. As always, questions, comments and suggestions are welcome, and may be directed to: waynerobertsau@yahoo.com.au Until next month: