July
2008
Updated: 1 July 2008
Welcome to the night skies of Winter, featuring Crux, Centaurus, Scorpius and Sagittarius
Explanatory Notes
:Rise and
set times are given for the theoretical horizon, which is a flat horizon all the
way round the compass, with no mountains, hills, trees or buildings to obscure
the view. Observers will have to make allowance for their own actual
horizon.
Transient phenomena are provided for the current month and the next. In the list of geocentric events, the nearer object is given first.
When a planet is referred to as ‘stationary’, it means
that its movement across the stellar background appears to have ceased, not that
the planet itself has stopped. With inferior planets (those inside the Earth’s
orbit, Mercury and Venus), this is caused by the planet heading either directly
towards or directly away from the Earth. With superior planets (Mars out to
Pluto), this phenomenon is caused by the planet either beginning or ending its
retrograde loop due to the Earth’s overtaking it.
Apogee and perigee: Maximum and minimum distances of the
Moon or artificial satellite from the Earth.
Aphelion and perihelion: Maximum and minimum distances of a
planet, asteroid or comet from the Sun.
A handspan at arm's length covers
an angle of approximately 20 degrees.
mv = visual magnitude
or brightness. Magnitude 1 stars are very bright, magnitude 2 less so, and
magnitude 6 stars are so faint that the unaided eye can only just detect them
under good, dark conditions. Binoculars will allow us to see down to magnitude
8, and the Observatory telescope can reach magnitude 15. The world's biggest
telescopes have detected stars and galaxies as faint as magnitude 30. The
sixteen very brightest stars are assigned magnitudes of 0 or even -1. The
brightest star, Sirius, has a magnitude of -1.44. Jupiter can reach -2.4, and
Venus can be more than 6 times brighter at magnitude -4.7, bright enough to cast
shadows. The Full Moon can reach magnitude -12 and the Sun magnitude -27. Each
magnitude step is 2.51 times brighter or fainter than the next one, i.e. a
magnitude 3.0 star is 2.51 times brighter than a magnitude 4.0. Magnitude 1.0
stars are exactly 100 times brighter than magnitude 6.0 (5 steps each of 2.51
times, 2.51x2.51x2.51x2.51x2.51 = 2.515 = 100).
Solar
System Sun:
Moon Phases: Lunations this month: #1058 and 1059
New
Moon: July 3
12:19
hrs
diameter = 33.1'
First Quarter: July
10
14:35
hrs
diameter = 30.1'
Full
Moon: July
18
17:59 hrs
diameter = 30.0'
Last
Quarter: July
26
4:42 hrs
diameter = 32.1'
New
Moon: August 1
20:13
hrs
diameter = 32.5'
First Quarter: August 9
6:20
hrs
diameter = 29.7'
Full
Moon: August
17
7:17 hrs
diameter = 30.7'
Last
Quarter: August
24
9:50 hrs
diameter = 32.3'
New Moon: August 31
5:58 hrs
diameter = 31.6'
Lunar Orbital Elements:
July 2:
Moon at perigee (359 527 km) at 7:27 hrs, diameter = 33.2'
July
6:
Moon at descending node at 1:53 hrs, diameter = 32.2'
July 14:
Moon at apogee (405 479 km) at 14:00 hrs, diameter = 29.5'
July
20:
Moon at ascending node at 13:25 hrs, diameter = 30.4'
July 30:
Moon at perigee (363 886 km) at 9:25 hrs, diameter = 32.8'
August
2:
Moon at descending node at 11:23 hrs, diameter = 32.3'
August 11:
Moon at apogee (404 574 km) at 6:27 hrs, diameter = 29.5'
August
16:
Moon at ascending node at 20:25 hrs, diameter = 30.6'
August 26:
Moon at perigee (368 689 km) at 13:58 hrs, diameter = 32.4'
August 29: Moon at
descending node at 20:30 hrs, diameter = 32.0'
Moon at 8 days after New, as on July 11
Moon at 9 days after New, as on July 12
The two photographs above show the Mare Imbrium area in the Moon's northern hemisphere. They were taken a day apart, just after First Quarter. Mare Imbrium (the Sea of Rains) is a large lava flow caused by the Imbrium Event - a cataclysmic collision of an asteroid with the Moon many millions of years ago. A comparison of the two photographs will show how the appearance of lunar features changes with the angle of the Sun.
In the first photograph, Mare Imbrium (left) is separated from Mare Serenitatis (right) by two ranges of mountains, the Alps to the north and the Apennines to the south. Two large craters at upper right are Aristoteles and Eudoxus. The straight Alpine Valley may be seen cutting through the Alps. Mt Piton (height 2000 metres) is visible as a bright spot with a shadow, due south of the southern end of the Alpine Valley. Archimedes is the large crater at left. It is a walled plain 80 kilometres in diameter with a flat floor. To its right are two bowl-shaped craters, Aristillus and Autolycus. These craters are all formed by impact with large meteors. Apollo 15 landed close by the Apennines, in a small enclosed area to the right and below Archimedes, on the picture's central vertical axis.
In the second photograph, the sunrise line (called the 'terminator') has moved to the left, revealing a large walled plain in the Alps, known as Plato. South of Plato, an isolated mountain protruding through the lava flow is called Mt Pico. Ripples in the lava, called 'wrinkle ridges', are visible. The crater at lower left is Timocharis, 42 kilometres in diameter.
A detailed map of the Moon's near side is available here.
A rotatable view of the Moon, with ability to zoom in close to the surface, and giving detailed information on each feature, may be downloaded here.Click
here for a photographic animation showing the lunar phases. It also shows the Moon's wobble or libration, and how its apparent size changes as it moves from perigee to apogee each month. It takes a little while to load, but once running is very cool !
Geocentric Events:
July 2:
Mars 40 arcminutes north of the star Regulus (Alpha Leonis,
mv= 1.36)
at 0:36 hrs
July 2:
Limb of Moon 26 arcminutes south of the star Elnath (Beta Tauri, mv= 1.65)
at 6:06 hrs
July 2:
Mercury at greatest elongation west (21.34º)
at 12:15 hrs, diameter = 7.9"
July 3:
Moon 2º north
of the star Mebsuta (Epsilon Geminorum, mv=
3.06)
at 10:06 hrs
July 4:
Moon 1.7º north
of Venus at 0:00 hrs
July 5:
Earth at aphelion at 3:10 hrs
July 6:
Moon 1.5º south
of star Regulus (Alpha Leonis,
mv= 1.36)
at 20:33 hrs
July 7:
Moon 2.1º south
of Mars at 1:54 hrs
July 7:
Moon 2.7º south
of Saturn at 5:33 hrs
July 9:
Jupiter at opposition at 17:28 hrs, diameter = 47.3"
July 11: Mars
38 arcminutes south of Saturn at 3:40 hrs
July 12:
Venus at perihelion at 6:16 hts, diameter = 9.8"
July 14:
Moon 1.1º north of the star Pi Scorpii (mv
= 2.89) at
7:59 hrs
July 14:
Limb of Moon 19 arcminutes south of the star Sigma Scorpii (mv=
2.9) at 17:53
hrs
July 14:
Limb of Moon 4 arcminutes south of the star Antares (Alpha Scorpii,
mv = 1.06) at 21:47 hrs
July 15:
Moon 1.5º north of star Tau
Scorpii (mv=
2.9) at
1:04 hrs
July 17: Limb of Moon
41 arcminutes south of the star Kaus Borealis (Lambda Sagittarii, mv= 2.82)
at 3:22 hrs
July 17: Limb
of Moon 37 arcminutes north of the star Nunki (Sigma Sagittarii,
mv = 2.0) at 15:06 hrs
July 17: Moon
2.6º south of Jupiter at 23:25 hrs
July 18:
Jupiter
1.6º south of the star Pi Sagittarii (mv = 2.88) at 1:25 hrs
July 20: Limb
of Moon 32 arcminutes north of Neptune at 22:44 hrs
July 22:
Mercury at perihelion at 2:24 hrs, diameter = 5.3"
July 23: Moon
4.1º north of Uranus at 4:10 hrs
July 28: Limb
of Moon 31 arcminures north of the Pleiades star cluster at 2:04 hrs
July 29: Limb
of Moon 32 arcminutes south of the star Elnath
(Beta Tauri, mv= 1.65)
at 15:06 hrs
July 30:
Mercury at superior conjunction at 5:58 hrs, diameter = 5.0"
July 30: Moon
1.2º north of the star Mebsuta (Epsilon
Geminorum, mv=
3.06) at 19:47 hrs
August 2: Limb of Moon 47
arcminutes south of Mercury at 1:28 hrs
August 2: Moon 2.1º south
of Venus at 22:54 hrs
August 3: Limb of Moon 38
arcminutes south of the star Regulus (Alpha Leonis,
mv= 1.36)
at 6:29 hrs
August 3: Moon 3.6º south
of Saturn at 20:22 hrs
August 6: Venus 1º north
of the star Regulus (Alpha Leonis,
mv= 1.36)
at 13:15 hrs
August 10:
Limb of Moon 29 arcminutes north of the star Pi Scorpii (mv
= 2.89) at
15:19 hrs
August 11:
Limb of Moon 16 arcminutes south of the star Sigma Scorpii (mv=
2.9) at 2:42
hrs
August 11:
Limb of Moon 4 arcminutes
north of the star Antares (Alpha Scorpii,
mv = 1.06) at 5:50 hrs
August 11:
Moon 2º north of the star Tau Scorpii (mv=
2.9) at
8:24 hrs
August 11: Venus 1.3º north of the star Rho Leonis (mv = 3.8)
at 21:30 hrs
August 13: Jupiter
2º south of the star Xi Sagittarii at
4:23 hrs
August 13: Limb of Moon
30 arcminutes south of the star Kaus Borealis (Lambda Sagittarii, mv= 2.82)
at 10:45 hrs
August 13: Limb
of Moon 11 arcminutes north of the star Nunki (Sigma Sagittarii,
mv = 2.0) at 22:28 hrs
August 14: Moon
2.4º south of Jupiter at 1:07 hrs
August 14: Venus 13 arcminutes south of
Saturn at 2:58 hrs
August 15: Mars 1.3 arcminutes south of the
star Zavijava (Beta Virginis,
mv = 3.6) at 13:07
hrs
August 16: Neptune at opposition at 3:25
hrs, diameter = 2.2"
August 16: Mercury 38 arcminutes south of
Saturn at 5:20 hrs
August 17: Full Moon 1.4º north of Neptune at 4:13 hrs
August 19: Moon
4.4º north of Uranus at 8:47 hrs
August 21: Mercury 56 arcminutes south of
Venus at 6:50 hrs
August 24: Moon 1.4º north of the Pleiades star cluster
at 7:57 hrs
August 25: Limb of Moon 44 arcminutes south
of the star Elnath
(Beta Tauri, mv= 1.65) at 21:52 hrs
August 27: Moon 1.6º north of the star
Mebsuta (Epsilon Geminorum, mv=
3.06)
at 3:23 hrs
August 28: Venus 30 arcminutes north of the
star Zavijava (Beta Virginis,
mv = 3.6)
at 19:38 hrs
August 30: Moon 1.5º south
of the star Regulus (Alpha Leonis,
mv= 1.36)
at 15:48 hrs
August 31: Moon 3.2º south
of Saturn at 11:43 hrs
The Planets for this month:
Mercury: Mercury reached inferior conjunction on June 8. The first week of July will be reasonably favourable to observe the innermost planet. Look in the morrning sky, just before dawn, just above the north-eastern horizon. It reaches greatest elongation west (21.5º) on July 2, when it will be a little less than a handspan to the left of the star Betelgeuse. On the morning of July 1, Mercury will sit midway between the waning crescent Moon and Betelgeuse. Mercury will pass on the far side of the Sun (superior conjunction) on July 30.
V
enus: The brightest planet passed through superior conjunction on June 9, and this month will reappear in the evening sky, setting after the Sun. Its appearance will be like a tiny Full Moon, as in the third picture below. By the end of July, Venus will have reached an angular distance of 14.4 degrees from the Sun. On August 13 and 14, Venus will be less than 17 arcminutes from Saturn.(The coloured fringes to the first and third images below are due to refractive effects in our own atmosphere, and are not intrinsic to Venus. The planet was closer to the horizon when these images were taken than it was for the second photograph, which was taken when Venus was at its greatest elongation from the Sun).
Cl
ick here for a photographic animation showing the Venusian phases. Venus is always far brighter than anything else in the sky except for the Sun and Moon. Up until last month, Venus appeared as a 'Morning Star', but this month it becomes an 'Evening Star' once again. Each of these appearances lasts about eight to nine months.Because Venus was visible as the 'Evening Star' and as the 'Morning Star', astronomers of ancient times believed that it was two different objects. They called it Hesperus when it appeared in the evening sky and Phosphorus when it was seen before dawn. They also realised that these objects moved with respect to the so-called 'fixed stars' and so were not really stars themselves, but planets (from the Greek word for 'wanderers'). When it was finally realised that the two objects were one and the same, the two names were dropped and the Greeks applied a new name Aphrodite (Goddess of Love) to the planet, to counter Ares (God of War). We use the Roman versions of these names, Venus and Mars, for these two planets.
Mars:
The Earth overtook the red planet last December 25, and Mars is now being left far behind, each month appearing a little smaller and fainter. It is in the constellation Leo, heading eastwards through the background stars. This movement is easily seen from night to night. In the first two weeks of July, Mars will be close to the star Regulus and Saturn. Mars will enter Virgo on August 9.With a magnitude of 1.7 on June 1, Mars is about as half as bright as the nearby star, Regulus. This is about as faint as it can get. Its angular diameter is about 4 arcseconds.
In this image, the south polar cap of Mars is easily seen. Above it is a dark triangular area known as Syrtis Major. Dark Sinus Sabaeus runs off to the left, just south of the equator. Between the south polar cap and the equator is a large desert called Hellas. The desert to upper left is known as Aeria, and that to the north-east of Syrtis Major is called Isidis Regio. Photograph taken in 1971.
Jupiter:
The largest planet is presently in the constellation Sagittarius and can be seen low in the east as soon as darkness falls. Jupiter will reach opposition (rising in the east-south-east as the Sun sets in the opposite direction) on July 9. Its angular diameter will be 47 arcseconds and its magnitude -2.7. The Full Moon will be 2.6 degrees to the right of Jupiter on July 17.
Saturn:
The ringed planet is now heading towards conjunction with the Sun, which will occur on September 4. At 6 pm at mid-month, Saturn and Mars will be only 30 degrees above the north-western horizon. The waxing crescent Moon will be close to Saturn on the nights of July 6 and 7.
Uranus:
As this planet was at western quadrature (rising at midnight) on June 13, Uranus is now becoming observable before midnight. At mid-month it will rise at about 9:35 pm. It is located in the constellation Aquarius, near the border with Pisces. Its magnitude is 5.8 and its angular diameter is 4 arcseconds.
Neptune: This icy blue planet passed through western quadrature on May 14. It is now observable in the late evenings, rising in the east at mid-month at about 7:25 pm. Its magnitude is 7.8 and its angular diameter is 2 arcseconds. Neptune is presently in the constellation of Capricornus. It will reach opposition on August 15.
Pluto:
The erstwhile ninth and most distant planet is a faint 13.9 magnitude object in the constellation Sagittarius, near the boundary with Serpens Cauda (The Snake's Tail). It is about 7.5 degrees north of M8, the Lagoon Nebula, and is about 2 degrees north of M23, a small open cluster. A powerful telescope is needed to detect Pluto, which even under excellent seeing conditions appears as a very faint star-like object. Its angular diameter is 0.14 arcseconds, less than one-fifteenth of the size of Neptune. In mid-July Pluto is about 40 degrees above the eastern horizon at 6:30 pm. It passed through opposition on June 21.
Planetary alignments
Until the end of July, Mars will be close to Saturn and Regulus, making an interesting grouping in the sky. Approaching through the stars of Leo, Mars will pass only 40 arcminutes below Regulus on the night of July 1/2. By July 10, Mars will pass by Saturn, being only 38 arcminutes above the ringed planet. On July 6, the Moon will join them. In August, Venus and Mercury will enter the grouping.
In August there will be an unusual 'dance of the planets' around the background stars. On August 3, the crescent Moon may be glimpsed low in the west-north-west soon after sunset, before darkness falls. It will be very thin and faint, and Saturn will appear 4 degrees to the right and above it. About 9 degrees (half a handspan) below the Moon, Venus may be discerned. Halfway between the Moon and Venus will be the star Regulus. Twelve degrees above Saturn will be Mars. Venus, Saturn and Mars will be equally spaced along a straight line a little over a handspan long.
The next night, August 4, the Moon will have moved up to Mars, which will be about four degrees to the right. The following night, the Moon will have moved further east, and will lie a little to the south of a line joining two third magnitude stars, Zaniah (above) and Zavijava (below).
On August 6, the Moon will lie between the constellation of Corvus, the Crow (a small quadrilateral of third magnitude stars), and the second magnitude star, Porrima (Beta Virginis). The next night, August 7, the Moon will be near the first magnitude star, Spica. On that date, Venus and Regulus will be just over a degree apart.
On August 7, the planets and stars mentioned will be strung out in a line like beads. Beginning at the west-north-western horizon, there will be Regulus and Venus, Saturn, Mars, Zavijava, Zaniah, Porrima, Spica and the Moon. Actually, Mercury is also in the alignment, being seven degrees below Venus, but, as it is only nine degrees from the Sun, the solar glare will make it a telescopic object only.
By August 10, Mercury will move close to Regulus, while Venus heads towards Saturn. On August 13, Venus and Saturn will be less than a degree apart, with Mercury less than four degrees below them.
August 15 will see Mercury, Venus and Saturn grouped together within a 2.6 degree circle, although the Sun is only 18.4 degrees away.
Staying together, Mercury and Venus will leave Saturn behind, as they head towards Mars, which is itself heading towards the star Zavijava. Mars will pass within 1.7 arcminutes of Zavijava at 1:40 pm on August 15, and will continue eastwards towards Zaniah. As it moves faster, Mercury will pass by Venus on August 21.
On August 27, Mercury and Venus will pass by Zavijava, and Mars will go by Zaniah. September 2 will provide a splendid grouping - Mercury and Venus will be near Zaniah, Mars will be near Porrima, and the crescent Moon will also be in attendance. September 4 will show a tighter grouping, but without the Moon.
By September 8, Mercury and Venus will both have caught up to Mars. On that date, Mercury will be 2.6 degrees to the left of Mars. Mercury will reach its greatest eastern elongation from the Sun (26.5 degrees) on September 10. On September 12, Venus and Mars will be only 20 arcminutes apart.
Between September 19 and 26, another fine grouping will take place, this time with Mercury, Venus, Mars and the star Spica. During this week, Mercury will reach its eastern stationary point, and will turn back towards the Sun, while Venus continues its easterly motion against the stars.
Mercury, Mars and Spica will gradually become lost in the solar glare, leaving only Venus left for us to observe. Venus will enter the constellation Libra on September 30, then Scorpius on October 18, then Ophiuchus on October 25, and then Sagittarius on November 9. Venus will arrive close to Jupiter (as seen from Earth) on December 1, with the crescent Moon between them, making a smiley face in the western sky.
☺
Meteor Showers:
Pegasids July 9 Waxing crescent Moon, 40% sunlit
ZHR = 8S Delta Aquarids
July 29 Waning crescent Moon, 19% sunlit ZHR = 20Alpha Capricornids
July 30
Waning crescent Moon, 12% sunlit ZHR =
8
Radiant: Near the star Algedi
Although most meteors are found in swarms associated with debris from comets, there are numerous 'loners', meteors travelling on solitary paths through space. When these enter our atmosphere, unannounced and at any time, they are known as 'sporadics'. Oan average clear and dark evening, an observer can expect to see about ten meteors per hour. They burn up to ash in their passage through our atmosphere. The ash slowly settles to the ground as meteoric dust. The Earth gains about 80 tonnes of such dust every day, so a percentage of the soil we walk on is actually interplanetary in origin. If a meteor survives its passage through the air and reaches the ground, it is called a 'meteorite'. One landed on a house in New Zealand recently, to the great alarm of the occupants. In the past, large meteorites (possibly comet nuclei or small asteroids) collided with the Earth and produced huge craters which still exist today. These craters are called 'astroblemes'. Two famous ones in Australia are Wolfe Creek Crater and Gosse's Bluff. The Moon and Mercury are covered with such astroblemes, and craters are also found on Venus, Mars, planetary satellites, minor planets, asteroids and even comets.
Comets:
Co
met 17P / Holmes is the largest object in the Solar SystemComet 17P/Holmes is an extremely faint periodic comet that returns every 6.88 years without anyone taking much notice. Its appearance late last year gained it world-wide attention, for it exploded on 24 October 2007. A vast sphere of dust and debris was ejected in an ever-growing cloud. Though the comet’s head is only some tens of kilometres across, the cloud rapidly reached the size of Jupiter by November 9 grew larger than the Sun. It has continued to enlarge until it is now over eleven million kilometres in diameter, eight times the Sun's diameter.
Before the eruption, the comet could only be seen through large telescopes, but the explosion caused it to brighten a millionfold within 36 hours, making it an obvious naked-eye object. Fourteen weeks later, it has faded to the limit of visibility without optical aid. It is still an easy object with binoculars. No-one knows how long it will remain visible, or even if there will be a second explosion, as occurred in 1892 and led to its discovery by Edwin Holmes.
Since the explosion was first detected, the comet has continued to expand dramatically. It is now the largest object in the solar system and has reached a size in the night sky much larger than the diameter of the Moon. As it is 240 million kilometres from us and further away than Mars, this is quite amazing. How a small comet could produce such an enormous cloud has not yet been explained. It is still growing in size.
In mid-November Comet Holmes experienced a ‘disconnection event’ - its faint, beautiful blue ion tail become detached from its head. This disruption does not necessarily signal a new outburst involving Comet Holmes. Comet tails can be disconnected by gusts of solar wind which trigger magnetic storms around the comet similar to the geomagnetic storms which cause aurorae on Earth. Such a storm and disconnection was observed earlier this year in the tail of Comet Encke.
Is it really the largest object in the Solar System? In diameter, yes, but of course the Sun is the most massive object by several orders of magnitude. Some comets produce tails many millions of kilometres long, so they would be longer, but not 'bigger'.
This image and the one below are taken with the same equipment and have the same plate scale. They show how the ejecta cloud surrounding the nucleus has dramatically expanded in 15 days. The sphere of ejecta surrounding the comet's nucleus is most clearly defined in the direction of the Sun, In the picture above this direction is towards the lower right. The magnitude 11.4 star GSC 3321:602 can be seen shining through the cloud at upper left. The diameter of the expanding cloud had reached 15 arcminutes and was still growing.
This image was taken on November 19. The Sun is to the right of the comet. The coma of Comet Holmes appears to swallow the much more distant star Mirfak. At this stage the comet is fading, and becoming swamped by moonlight from the waxing gibbous Moon.
This image was taken at the prime focus of the RCOS reflector, and has a much larger plate scale than the other image above. It shows the interior of the ejecta cloud, which fills the frame and has now become the comet's coma. The nucleus or head is just right of centre, and the beginnings of the tail stream off to the left. Image acquired on December 3.
Click here for more photographs taken from Starfield Observatory, Nambour.
T
he LINEAR robotic telescope operated by Lincoln Near Earth Asteroid Research is used to photograph the night skies, searching for asteroids which may be on a collision course with Earth. It has also proved very successful in discovering comets, all of which are named ‘Comet LINEAR’ after the centre's initials. This name is followed by further identifying letters and numbers. Generally though, comets are named after their discoverer, or joint discoverers. There are a number of other comet and near-Earth asteroid search programs using robotic telescopes and observatory telescopes, such as:Nearly all of these programs are based in the northern hemisphere, leaving gaps in the coverage of the southern sky. Needless to say, Comet Machholz was discovered in one of these gaps by an amateur astronomer with a small backyard observatory.
To find out more about current comets, including finder charts showing exact positions and magnitudes, click
here. To see pictures of these comets, click here.
Deep Space
Sky Charts and Maps available on-line
There are some useful representations of the sky available here. The sky charts linked below show the sky as it appears to the unaided eye. Stars rise four minutes earlier each night, so at the end of a week the stars have gained about half an hour. After a month they have gained two hours. In other words, the stars that were positioned in the sky at 8 pm at the beginning of a month will have the same positions at 6 pm by the end of that month. After 12 months the stars have gained 12 x 2 hours = 24 hours = 1 day, so after a year the stars have returned to their original positions for the chosen time. This accounts for the slow changing of the starry sky as the seasons progress.
The following interactive sky charts are courtesy of Sky and Telescope magazine. They can simulate a view of the sky from any location on Earth at any time of day or night between the years 1600 and 2400. You can also print an all-sky map. A Java-enabled web browser is required. You will need to specify the location, date and time before the charts are generated. The accuracy of the charts will depend on your computer’s clock being set to the correct time and date.
To produce a real-time sky chart (i.e. a chart showing the sky at the instant the chart is generated), enter the name of your nearest city and the country. You will also need to enter the approximate latitude and longitude of your observing site. For the Sunshine Coast, these are:
latitude: 26.6o South longitude: 153o East
Then enter your time, by scrolling down through the list of cities to "Brisbane: UT + 10 hours". Enter this one if you are located near this city, as Nambour is. The code means that Brisbane is ten hours ahead of Universal Time (UT), which is related to Greenwich Mean Time (GMT), the time observed at longitude 0o, which passes through London, England.
Click here to generate these charts._____________________________________
The first, circular chart will show the full hemisphere of sky overhead. The zenith is at the centre of the circle, and the cardinal points are shown around the circumference, which marks the horizon. The chart also shows the positions of the Moon and planets at that time. As the chart is rather cluttered, click on a part of it to show that section of the sky in greater detail. Also, click on Update to make the screen concurrent with the ever-moving sky.
The stars and constellations around the horizon to an elevation of about 40o
can be examined by clicking onView horizon at this observing site
.The view can be panned around the horizon, 45 degrees at a time. Scrolling down the screen will reveal tables showing setup and customising options, and an Ephemeris showing the positions of the Sun, Moon and planets, and whether they are visible at the time or not. These charts and data are from YourSky, produced by John Walker.
The charts above and the descriptions below assume that the observer has a good observing site with a low, flat horizon that is not too much obscured by buildings or trees. Detection of fainter sky objects is greatly assisted if the observer can avoid bright lights, or, ideally, travel to a dark sky site. On the Sunshine Coast, one merely has to travel a few kilometres west of the coastal strip to enjoy magnificent sky views. On the Blackall Range, simply avoid streetlights. Allow your eyes about 15 minutes to become dark-adapted, a little longer if you have been watching television. Small binoculars can provide some amazing views, and with a small telescope, the sky’s the limit.
The Eta Carinae Nebula, 14 degrees above the Southern Cross tonight
The
The
se descriptions of the night sky are for 8 pm on July 1 and 6 pm on July 31. They start at the western horizon.Close to the western horizon is the second magnitude star Alphard. This is an orange star that was known by Arabs in ancient times as 'The Solitary One’, as it lies in an area of sky with no bright stars nearby.
In the north-west, Leo the Lion is preparing to set. It will have completely disappeared by 10.30 pm. The bright star Regulus (Alpha Leonis) marks the Lion’s heart. A handspan to the right and above Regulus is Denebola, a white star marking the tip of the lion's tail. It is about 30 degrees above the north-western horizon. We see the lion upside-down from the Southern Hemisphere. Regulus is the western-most star in a pattern called 'The Sickle' (or reaping-hook). It marks the end of the Sickle's handle, with the other end of the handle, the star Eta Leonis, below and to the right. The blade of the Sickle curves around clockwise from Eta Leonis to the horizon. The Sickle forms the mane and head of the lion, when observed right-way-up. The Sickle is just touching the theoretical horizon at this time tonight.
The constellation Leo, as we see it from Australia. Regulus is above centre left, and Denebola above centre right. The Sickle curves down from Regulus.
High in the north, (about 43 degrees above the horizon, and about 10 degrees west of the meridian or north-south line) we can find the fourth brightest star in the night sky, Arcturus. It is outshone only by Sirius, Canopus and Alpha Centauri. Arcturus differs from those just named, for it is an obvious orange colour, a K2 star of zero magnitude. It is a particularly beautiful star, and is the brightest in the constellation of Boötes, the Herdsman. Boötes is due north (culminating) at this time of night.
East of Boötes and above the north-north-eastern horizon is a fainter circle of fourth magnitude stars, Corona Borealis, the Northern Crown. The brightest star in the Crown is named Alphecca, and it shines at magnitude 2.3.
East of the Northern Crown is Hercules, stretching from the north-north-eastern horizon upwards. Rising in the north-east is a bright white A0 star, Vega, which is the fifth brightest star, after Arcturus. Vega is the main star in the small constellation of Lyra the Lyre, which contains the famous Ring Nebula, M 57.
About fifteen degrees (a little less than a handspan) to the right of Vega can be seen Albireo, a beautiful double star with contrasting colours. It is the highest star of the Northern Cross, Cygnus.
Rising above the eastern horizon is the great main-sequence star Altair. This A7 white star is the eleventh brightest in the heavens. Altair is also known as Alpha Aquilae, as it is the brightest star in the constellation of Aquila, the Eagle. It marks the heart of the eagle, and is flanked by two lesser stars marking each wing-tip, Gamma Aquilae and Beta Aquilae. This threesome, making a short horizontal line in the east, is easy to find.
Just to the west of the zenith is the next zodiacal constellation after Leo, Virgo, the Virgin. It is a large but fairly inconspicuous constellation, but it does have one bright star, Spica, which is an ellipsoidal variable star whose brightness averages magnitude 1. This star, also known as Alpha Virginis, is a hot, blue-white star of spectral type B2. It is the sixteenth brightest star, and the rest of the constellation Virgo lies to the north-west of it. Tonight, Spica is at an altitude of 65 degrees, between the zenith and Corvus. It is roughly halfway between Arcturus and the Southern Cross.