Mercury remains a morning object for observers in the tropics and Southern Hemisphere for about the first 10 days of July. The nearest planet to the Sun may be spotted about 45 minutes before sunrise in the twilight sky low down above the east-northeastern horizon; brightening from magnitude -0.1 to -0.9 during this time period. Mercury is then unobservable for the remainder of the month as it moves closer ever in the sky to the Sun. The planet reaches superior conjunction on July 23rd.
From northern temperate latitudes Mercury is unobservable during July.
The diagram below shows the June / July morning apparition of Mercury from a latitude of 35S (approx. equal to Sydney, Cape Town and Santiago). Positions of the planet are displayed 45 minutes before sunrise.
Venus continues its run as brilliant evening star this month although from northern temperate locations the observation period shortens noticeably and from about the middle of the month the brightest planet will be lost to the sunset. From more southerly latitudes Venus remains visible throughout July.
On July 10th, Venus attains its greatest brilliance when it peaks at magnitude -4.7. Before this on July 1st it passes only 0.4 degrees south of Jupiter (mag. -1.8) with Venus 15 times the brighter of the pair. Another conjunction occurs on July 19th when the waxing crescent Moon passes 0.4 degrees south of Venus with an occultation visible from northeastern Australia and the French Polynesia (1:07 UT).
On July 23rd, Venus reaches a stationary point in Leo, afterwards retrograde motion commencing. It then draws back towards the Sun with the planet once again passing south of Jupiter on July 31st although this time the separation is more than 6 degrees. Of course the events described during the second half of July are only visible from more southerly climes.
During the month the Venus phase decreases from 33% to a very slim 8% crescent.
Earth is at aphelion - furthest from the Sun - on July 6th at a distance of 1.017 AU (152 million kilometers or 94.5 million miles).
Mars reached solar conjunction on June 14th. The Red planet is currently located on the far side of the Sun and remains unsuitable placed for observation throughout July.
Jupiter, mag. -1.8, continues to be visible as an early evening object during July although observers at northern temperate latitudes are likely to lose the planet to the bright long evening twilight during the third week of the month. The largest planet of the Solar System can be seen low down towards the western horizon as soon as it dark enough.
Now moving direct in Leo, Jupiter's long evening period of visibility is almost over as it heads towards next month's solar conjunction. As previously mentioned, much more brilliant Venus will pass less than half a degree south of Jupiter on July 1st. For those located at tropical and southern latitudes another Venus - Jupiter conjunction occurs on July 31st. On this occasion Venus passes 6 degrees south of Jupiter.
The thin waxing crescent Moon passes 4 degrees south of Jupiter on July 18th.
Only two months passed opposition, Saturn remains an evening object during July. The beautiful planet famous for it's wonderful ring system continues to move slowly retrograde amongst the faint stars of Libra. It appears to the naked eye as off-white or creamy "star" located 10 degrees northwest of orange/red first magnitude red giant Antares (α Sco mag. +1.0).
Saturn is visible as soon as it's dark enough towards the south-southeast from northern temperate latitudes or towards the northeast from south latitudes. It sets just after midnight at months end from northern latitudes although two hours later for those further south.
The planet fades slightly from magnitude +0.2 to +0.4 with its apparent diameter shrinking from 18.1 to 17.3 arc seconds as the month progress.
On July 26th, the waxing crescent Moon passes 2 degrees north of Saturn.
Uranus is now well placed for observation amongst the stars of Pisces. At magnitude +5.8 Uranus is actually visible to the naked eye, albeit faintly. To achieve this goal a dark moonless site is required along with good seeing conditions and a good star chart to pinpoint the exact location.
At the start of July from northern temperate locations, Uranus rises 4 hours before sunrise and by months end is visible from about midnight. The visibility period from locations further south is even better with Uranus visible in the evening sky by months end.
On July 9th the last quarter Moon passes 0.8 degrees south of Uranus with an occultation visible from Western Australia and the Southern Indian Ocean at 2:47 UT. Two weeks later on July 26th, Uranus reaches its first stationary point signaling the beginning of this year's opposition period. The planet then commences retrograde motion.
Neptune (mag. +7.8) is moving retrograde in Aquarius as it heads towards opposition on September 1st. The eighth and most distant planet from the Sun is positioned about 30 degrees southwest of the Great Square of Pegasus and a few degrees southwest of star lambda (λ) Aqr (mag. +3.7). It now rises before midnight from northern temperate latitudes and up to a couple of hours earlier from locations further south.
Although observers may be able to spot Uranus with the naked eye they have no chance do the same with Neptune, it's far too faint. However, the planet is relatively easy to spot binoculars.
On July 6th, the waning gibbous Moon passes 3 degrees north of Neptune.
Capella is the sixth brightest star in the night sky and the third brightest in the northern celestial hemisphere. It's also the northernmost first magnitude star with a declination of nearly +46 degrees and therefore circumpolar (never sets) from many northern temperate locations. However, despite this it's visible at one time or another from almost all inhabited countries including all of Australia, almost all of New Zealand and Argentina. It's not visible from Antarctica and the Falkland Islands.
Capella has an apparent magnitude of +0.08, which mean it's marginal fainter than Vega. To the naked eye the brightness difference is difficult to notice but what's obvious is the colour contrast, deep yellow tinged Capella against stark blue-white Vega. Capella is the standout bright member of the relatively large constellation of Auriga, the Charioteer. The Milky Way passes through the heart of Auriga and therefore it contains numerous bright open clusters, nebulae and interesting stars.
The name Capella is Latin and means "small female goat". The star marks the left shoulder of the Charioteer or according to Ptolemy's 2nd century Almagest, the goat that the charioteer is carrying. The three faint stars that form a triangle close beside it are the Haedi, or the "Kids". In Greek Mythology, Capella represented the goat Amalthea whose horn was accidentally broken off by Zeus. The horn was transformed into the Cornucopia or the "horn of plenty", which would be filled with whatever its owner desired. To the Chinese it was one of the stars making up Woo Chay, the Five Chariots (the others Beta, Theta, Kappa and Gamma Aurigae). To the Arabs it was known as Al Rakib, the Driver as it was often visible in the early evening sky before other stars came into view.
Some ancient astronomers including Ptolemy referred to Capella as reddish but this has to due to atmospheric affects, there isn't the slightest chance the star has changed colour in the past 2000 years. In 1899, William W. Campbell of the Lick Observatory, Mount Hamilton, California and Hugh Newall at Cambridge in England measured the spectrum of Capella and found that the star was not a single star but a binary. The components are so close together they are incredibly difficult to separate visually.
Both components are similar. The brighter Aa yellow star is a type G1 with a diameter of 17 million kilometers (10.6 million miles) or 12 times that of the Sun. The Ab star has a spectral type K0 and therefore orange with a diameter of 12.5 million kilometers (7.8 million miles). This is equivalent to 9 times the size of the Sun. They have masses of 2.7 and 2.6 times and are 90 and 70 more times luminous than our star respectively.
Once it was realized Capella was a binary system immediate efforts were made to visually resolve the components. A partial success was achieved in 1901, when astronomers at Greenwich noted the star as "elongated" when using the 28-inch refractor. Confirmation was achieved in 1919 by John Anderson and Francis Pease using the 100-inch Hooker telescope at Mount Wilson, Los Angeles. However, the star remains as a single point of light in amateur scopes.
Astronomers recently discovered that the Capella system contains a second pair of red dwarfs stars. They are designated Capella H and Capella L and are located around 10,000 astronomical units from the main Aa / Ab pair.
The Capella star system is currently located 42.8 light-years distant from Earth. For 50,000 years from 210,000 BC to 160,000 BC, Capella was the brightest star in the night sky. At best it shone at magnitude -0.82 and was 27.9 light-years distant.
NGC 2360 is an open cluster visible with binoculars in the constellation of Canis Major. It was the first deep sky discovery made by Caroline Herschel - the younger sister of William Herschel - on February 26, 1783. She described it as "a beautiful cluster of pretty compressed stars near 1/2 degree in diameter." It's also known as Caroline's Cluster, Caldwell 58 and Melotte 64.
William included the cluster in his 1786 catalogue of 1000 clusters, crediting his sister as the discoverer. At magnitude +7.2, NGC 2360 is not visible to the naked eye but it's an easy binocular object and a fine sight through small telescopes. The cluster is positioned 8 degrees east-northeast of the brightest star in the night sky Sirius (α CMa - mag. -1.47) and lies 3.5 degrees directly east of gamma CMa (γ CMa - mag. +4.1). At the western edge of NGC 2360 is an unrelated star, HD 56405 (mag. +5.5).
NGC 2506 is a magnitude +7.6 rich open cluster located in the constellation of Monoceros. Although its member stars are faint the cluster itself appears quite bright and can be seen with a pair of binoculars. Through telescopes it's an impressive object and of all the Monoceros open clusters it's probably the finest. With an age of 1.1 billion years old this is an old cluster. For comparison, M45 (The Pleiades) in Taurus is a youthful 115 million years old with the Hyades cluster 625 million years old. However, NGC 2506 is not nearly as old as the 4 billion years of M67 in Cancer.
William Herschel discovered NGC 2506 on February 23, 1791. Locating the cluster can sometimes be a bit tricky as it's positioned in an area of sky devoid of bright stars. It can be found 5 degrees east-southeast of alpha Mon (α Mon - mag. +3.94) the brightest star in Monoceros. Located 19 degrees southwest of NGC 2506 is the brightest star in the sky, Sirius (α CMa - mag. -1.46). Although α Mon and Sirius are the brightest stars in their respective constellations the difference in apparent brightness between them is enormous, more than 100x.
Large open cluster M48 lies 6 degrees northeast of NGC 2506 with open cluster pair M46 and M47 positioned 6 degrees southwest of NGC 2506. They are best seen during the months of December, January and February.
Lynx is home to the fascinating globular cluster NGC 2419. Although visually faint and small what makes NGC 2419 special is its distance; at 275,000 light-years it's one of the furthest known Milky Way globulars. In fact, twentieth century American astronomer Harlow Shapley nicknamed it "The Intergalactic Tramp" believing it to have possibly broken away from the Milky Way and headed off into deep inter galactic space. However, recent observations indicate Shapley hypothesis was incorrect and NGC 2419 is still gravitationally bound to the Milky Way just moving in a highly eccentric orbit.
NGC 2419 or Caldwell 25 was discovered by William Herschel on December 31, 1788. It's located 275,000 light-years from the Solar System and about 300,000 light-years from the galactic centre, almost twice as far away as the Large Magellanic Cloud. At such a distance it's estimated NGC 2419 will take about 3 billion years to complete a single orbit around the centre of the galaxy.
NGC 2419 is positioned 7 degrees north and slightly east of Castor (α Gem - mag. +1.58) the second brightest star in Gemini. About 4 arc minutes west of NGC 2419 is a mag. +7.2 star with a double star of mag. +7.9 a few more arc minutes further west. Even Herschel with his super telescopes of the time couldn't resolve NGC 2419 into stars. William Parsons, the 3rd Earl of Rosse, using his 72-inch (1.83 m) reflecting telescope at Birr Castle in Ireland - the largest optical telescope in the world at the time - was first the first to do so in 1850.
NGC 4236 is a tenth magnitude barred spiral galaxy in Draco that's visible through small telescopes, although best seen with larger instruments. The galaxy was discovered by German born British astronomer William Herschel on April 6, 1793 and is a member of the Ursa Major or M81 group of galaxies that contains at least 34 galaxies, including spectacular M81 (Bode's galaxy) and M82 (Cigar galaxy).
NGC 4236 is located in the far northern constellation of Draco about 15 degrees north of the seven stars that form the famous "Plough" or "Big Dipper" asterism of Ursa Major. The galaxy is positioned two-thirds of the way along an imaginary line connecting stars lambda Dra (λ Dra - mag. +3.8) and kappa Dra (κ Dra - mag. +3.9). Star HD 106574 (mag +5.7) is 0.75 degrees directly north of NGC 4236.
Due to its high northerly declination, NGC 4236 is a Northern Hemisphere object. The best months to look for it are March, April or May although from most northern locations it's visible all year round and never sets. It can be seen from the Southern Hemisphere but only from latitudes north of 20 degrees south and even then appears low down above the northern horizon at best.
Mercury passed inferior conjunction on May 30th and was therefore positioned too close to the Sun to be observable. However, it moves rapidly out from the Sun so that two weeks later it becomes visible as a morning object for observers in the tropics and Southern Hemisphere. The planet subsequently climbs higher in the sky and brightens each day until it reaches a peak altitude on June 24th, the date of greatest elongation west (22.5 degrees from the Sun). Also on this day Mercury passes 2 degrees north of orange giant star Aldebaran (α Tau) the brightest star in the constellation of Taurus "the Bull". At magnitude +0.4 Mercury is half a magnitude brighter than the star with the pairing making a lovely early morning binocular / small telescope view.
It should also be noted that once past greatest elongation west, Mercury continues to brighten as it begins to draw into the Sun. For example, the planet shines at mag. +1.7 on June 15 but by month's end it has brightened to magnitude -0.1. From northern temperate latitudes, Mercury is a more difficult catch as it battles against the long morning twilight. The best time to try and catch it is for a few days on and around June 24th when it should be visible low down above the east-northeast horizon just before sunrise. A pair of binoculars will easily show the magnitude +0.4 planet although be careful not to confuse it with nearby Aldebaran.
The diagram below shows the June / July morning apparition of Mercury from a latitude of 35S (approx. equal to Sydney, Cape Town and Santiago).
The brightest object in western sky after sunset is Venus with the planet remaining well placed for observation throughout the month. On June 6th it reaches greatest elongation and on this day is positioned 45 degrees east of the Sun.
Currently moving eastward the declination of Venus decreases by 10 degrees as it moves from Gemini into Cancer and then into Leo. Consequently, the planets period of visibility decreases from 3.5 hours to less than 2 hours for observers located at Northern Hemisphere latitudes. For those living in the Southern Hemisphere the period of visibility remains around the 3-hour mark for the complete month.
There are three superb Venus conjunctions visible during June. On June 12th and 13th the planet slides less than a degree north of splendid open star cluster M44 "The Beehive", making a wonderful binocular sight. Then on June 20th, the waxing crescent Moon passes 6 degrees south of the planet. Finally Venus closes the gap on Jupiter and on the last day of June the two planets will be less than half a degree apart. To the naked eye they will appear stunning. Through binoculars and a telescope at low power both planets will appear in the same field of view, although Venus is about 10x the brighter of the pair.
The magnitude of Venus increases slightly from -4.3 to -4.4 with its phase decreasing from 53% to 34% during June.
Mars reaches solar conjunction on June 14th and therefore is unobservable throughout the month.
Jupiter remains an early evening object throughout June although it's now long past opposition and heading towards solar conjunction. The largest planet of the Solar System is visible towards the west as soon as it gets dark, but sets before midnight by months end. It's brightness decreases slightly from magnitude -1.9 to -1.8 as the month progresses.
The giant planet continues on a direct motion path, starting the month in Cancer before passing into Leo on June 10th. At the start of June, brighter Venus (mag. -4.3) is located about 20 degrees from Jupiter. It then closes the gap each subsequent evening before catching Jupiter at the tail end of the month. On June 30th, the two planets will be less than half a degree apart.
On June 21st, the waxing crescent Moon passes 5 degrees south of Jupiter.
This month Venus and Jupiter dominate the early evening sky with Mercury visible for a time in the morning sky but the night belongs to Saturn. The planet is only just past opposition (May 23rd) and remains superbly placed for observation during June. It's currently moving retrograde in western Libra and visible towards the southeast (NH) / east (SH) as darkness falls. Saturn can be observed practically all night and is better seen from southern latitudes where it's situated much higher in the sky.
Since now past opposition the apparent brightness and apparent size of Saturn will gradually decrease as the Earth moves away. During June, its magnitude decreases from 0.0 to +0.2 with the apparent diameter shrinking slightly from 18.5 to 18.0 arc seconds.
Saturn's wonder of course is its ring system. They are currently tilted at 24 degrees from our perspective and even a small 80mm (3.1-inch) telescope will easily show them. At magnification 100x the rings are nicely visible, tightly circling the central gem of Saturn. Increase the magnification to 200x or greater (seeing permitting) and the ring shadow on the planet, the darker outer A ring, the lighter B ring, subtle shadings and colour changes on Saturn's surface may be detected.
A good quality larger telescope, with its increased light gathering capability and higher magnification capability will of course show greater detail. For example, a 200mm (8-inch) scope can under good seeing be used to up to 400x magnification and will also reveal the 0.7 arc seconds wide Cassini division, the Enke division, the hazy C-ring as well as up to half a dozen of Saturn's satellites.
The almost full Moon passes 2 degrees north of Saturn on June 1st and again on June 29th.
Uranus starts the month as a morning object in Pisces with the planets visibility steadily improving as the month progresses. For Northern Hemisphere based observers at the start of June, it's visible above the eastern horizon for about an hour before twilight interferes. By months end the planet is much higher in the sky, rising more than 4 hours before the Sun.
Observers located further south have it even better with Uranus well placed in the morning sky throughout the month. At the beginning of the June the planet rises some 4 hours before the Sun and by the end of the month it's visible before midnight.
Uranus is a distant ice giant that shines at magnitude +5.9 and therefore bright enough to be seen with the naked eye from a dark site. Unfortunately most people don't have the luxury of such fine seeing conditions and therefore a pair of binoculars or small telescope is usually required to spot the planet.
On June 11th, the waning crescent Moon passes 0.5 degrees south of Uranus and an occultation is visible from South and East Australia, New Zealand, Fiji and Samoa (20:26 UT).
Neptune shines at mag. +7.9 and is now well placed for observation amongst the stars of Aquarius. By months end the most distant planet of all rises around midnight from northern temperate latitudes and much earlier for those located further south. It's currently located about 30 degrees southwest of the Great Square of Pegasus and a few degrees southwest of star lambda (λ) Aqr (mag. +3.7).
On June 9th, the last quarter Moon passes 3 degrees north of Neptune. Three days late Neptune reaches its first stationary point, signaling the beginning of this year's opposition period. The planet then commences retrograde motion.
NGC 2261 is a curious variable reflection nebula in Monoceros that's known as Hubble's Variable Nebula. It was discovered by William Herschel in 1783 and is illuminated by variable star R Monocerotis (R Mon). The nebula is unusual in that it changes shape over just a period of days and can vary by up to 2 magnitudes in brightness. The variations are believed to be due to periodic changes in the amount of dust surrounding R Mon, thus affecting the amount of light that reaches us. With an apparent magnitude of +9.0, it can be spotted with binoculars under dark skies.
The variability of R Mon (between magnitudes +10 and +12) was discovered at the Athens Observatory in 1861 but it wasn't until 1916 that Edwin Hubble realised that the nebula also changes in brightness. The variations are such that even on images taken days apart structural changes can be observed.
NGC 2261 was chosen as the "first light" photograph on January 26, 1949 for the 200-inch (5.1 m) Hale reflecting telescope under the direction of American astronomer Edwin Powell Hubble. At the time, the newly constructed Hale telescope was the largest telescope in the World and remained so until 1976. The nebula is listed as number 46 in the Caldwell catalogue.
NGC 2362 is a small compact young open cluster in Canis Major that surrounds bright star Tau Canis Majoris (τ CMa - mag. +4.37). This attractive grouping of 60 stars is packed into an area spanning just 6 arc minutes of apparent sky. The apparent magnitude of the cluster is given as +4.1, however the value is misleading as its skewed significantly because of the brilliance of τ CMa. The remaining members of NGC 2362 are much fainter, the brightest being of 7th magnitude.
Finding NGC 2362 is not difficult. It's located 2.75 degrees northeast of Wezen (δ CMa - mag. +1.83) the third brightest star in Canis Major. Sirius (α CMa) the brightest star in the night sky (mag. -1.46) is positioned 11 degrees to the northwest. Tau CMa a spectroscopic multiple system that shines with a combined light of tens of thousands times that of the Sun is the stand out cluster member and bright enough to be seen with the naked eye. For comparison, the Sun at the same distance would shine at a feeble magnitude +15.
NGC 2362 was discovered by Giovanni Batista Hodierna sometime before 1654 and then re-discovered by William Herschel on March 4, 1783. It's best seen from southern latitudes during the months of December, January and February.
NGC 457 is the brightest open cluster in Cassiopeia and one of the finest objects of its type in the northern sky. At magnitude +6.4, it's just beyond naked-eye visibility but easily seen with binoculars and a beautiful sight through telescopes. The brightest cluster stars are arranged in prominent lines and curves lines appearing to resemble an Owl shape, hence the popular name "the Owl Cluster". It's located 7,900 light-years distant.
NGC 457 was discovered by William Herschel in 1787. Finding the Owl Cluster is easy; it's positioned two degrees south-southeast of eclipsing binary star system Ruchbah (δ Cas - mag. +2.7). This star is one component of the characteristic "W" asterism of Cassiopeia. The brightest star inside NGC 457 is Phi Cas (φ Cas - mag. +5.0). Despite not being a member of the cluster, this foreground star is visible to the naked eye. Together with another non-cluster star - seventh magnitude HD 7902 (HIP 6229) - they form the bright eyes of the Owl greatly adding to the splendour of the view through backyard scopes.
NGC 457 is best seen from Northern Hemisphere latitudes during August, September and October. It appears high in the sky and even overhead from many locations. From latitudes greater than 32N, the Owl is circumpolar and never sets.
NGC 752 is a large spawling open cluster in the constellation of Andromeda. With an apparent magnitude of +5.7, it's visible to the naked eye from a dark site appearing as a large unresolved fuzzy patch of light. The cluster is one of the finest large open clusters in the sky and contains over 70 stars spread across a huge 1.25 degrees of apparent sky. Due to its size, NGC 752 is best observed with binoculars or through wide field telescopes at low powers.
NGC 752 is located 5 degrees south and slightly west of outstanding double star Almach (γ And - mag. +2.1) the third brightest star in the constellation. It was discovered by Caroline Herschel on September 29, 1783 although it was probably observed sometime before 1654 by Italian astronomer Giovanni Battista Hodierna. Caroline's brother William Herschel subsequently added it to his catalogue a couple of years later. It's best seen from northern latitudes during the months of October, November and December. The cluster is number 28 in the Caldwell catalogue.
NGC 2775 is a magnitude +10.5 spiral galaxy located in the constellation of Cancer, close to its border with Hydra. The galaxy is unusual in that it contains a very smooth nucleus with multiple spiral arms extending outwards from the central region. What makes the spiral arms interesting is their incredible complex detail, tightly wound structures and active star formation. Amateur astronomers should also keep their eye on this galaxy; it's been host to 5 supernovae explosions in the past 30 years and you never know when the next one will go off!
To find NGC 2775 look for the head of Hydra "the Sea Serpent". The asterism of stars that forms the head are ω Hyd (mag. +5.0), ζ Hyd (mag. +3.1), ρ Hyd (mag. +4.4), ε Hyd (mag. +3.4), δ Hyd (mag. +4.1), σ Hyd (mag. +4.5) and η Hyd (mag. +4.3). None of the stars are particularly bright but all can be seen with the naked eye. The galaxy is positioned a few degrees east and slightly north of this grouping.
NGC 2775 was discovered by William Herschel in 1783 and is best seen during the months of February, March and April. The galaxy is located 55.5 million light-years from Earth and has an actual diameter of 70,000 light-years. It's estimated to contain 100 billion stars. NGC 2775 is number 48 in the Caldwell catalogue.
NGC 2477 is a stunning open cluster located in the Milky Way rich constellation of Puppis. It's arguably the constellations finest cluster which also contains other superb examples such as M46, M47 and M93. At magnitude +5.8, NGC 2477 is faintly visible to the naked eye but easily seen with binoculars and a fantastic telescope object, especially in medium to large scopes. It's listed as number 71 in the Caldwell catalogue.
The cluster was discovered by French astronomer Nicolas Louis de Lacaille during his tour of South Africa in 1751-52. In total it contains about 300 stars packed into an area 27 arc minutes in diameter with the brightest member star shining at magnitude +9.8. The four-magnitude difference between the combined cluster magnitude and the brightest component is an indication of how rich the cluster is.
NGC 2477 is too far south to have been included in Charles Messier's catalogue, but if he had observed from a more southerly latitude than Paris he almost certainly would have noticed this striking object. Twentieth century America astronomer Robert Burnham described NGC 2477 as "probably the finest of the galactic clusters in Puppis".
The cluster is easily found 2 degrees northwest of zeta Pup (ζ Pup - mag. +2.2) and just northwest of magnitude +4.5 star, b Pup. Located 1.5 degrees west of NGC 2477 and in the same binocular field of view lies large loose open cluster NGC 2451. Another binocular open cluster, NGC 2546, is positioned 4 degrees east of NGC 2477. They are best seen from southern latitudes during the months of December, January and February.
NGC 40 is a planetary nebula located in the northern constellation of Cepheus. It was discovered by William Herschel on November 25, 1788 who described it as "a 9th magnitude star, surrounded with milky nebulosity". Herschel used his 475mm (18.7) inch telescope to make the discovery but for today's amateur astronomers such a large scope isn't required, it can be glimpsed with just a 100mm (4-inch) instrument. NGC 40 is also known as the Bow Tie nebula, a nickname it shares with another planetary nebula, NGC 2440 in Puppis. It's listed as number 2 in the Caldwell catalogue.
NGC 40 is located just over 17 degrees from the North Celestial Pole and therefore circumpolar from most northern latitudes. It's one of the finest examples of its type in the far northern part of the sky. The best time to look for the nebula is during October, November and December when it appears highest in the sky during early evening. The Bow Tie nebula is also visible from most tropical locations although lower down. However, from southern temperate latitudes it's not visible at all.
Locating NGC 40 can be precarious as it's positioned in a star poor region of eastern Cepheus. One method to find it is by imagining a line connecting Errai (γ Cep - mag. +3.21) and γ Cas (mag. +2.15). The planetary lies approximately one-third of the way along this line.
NGC 188 is an open cluster located in the far northern constellation of Cepheus. It was discovered by John Herschel - the son of William Hershel - on November 3, 1831. He originally recorded it as h 34 in his 1833 catalogue and then included it as GC 92 in his subsequent General Catalogue of 1864. The cluster finally became NGC 188 in John L.E. Dreyer's New General Catalogue of 1888.
NGC 188 is the northernmost open cluster in the sky, it's positioned only 4.75 degrees from the North Celestial Pole. Located at such a northerly declination means the cluster is circumpolar from almost the entire northern hemisphere. It can be seen from the Southern Hemisphere but only from latitudes north of 5 degrees south. Even then it never climbs more than a few degrees above the northern horizon.
Although comet Lovejoy has faded significantly since it reached naked eye brightness a few months ago it should still remain an easy telescope target during May. During the month the comet continues on its northerly path heading towards a close pass of Polaris and the North Celestial Pole.
Location and star chart
Lovejoy spends the first couple of days of May in northern Cassiopeia before moving into Cepheus where it remains until the 28th. The surrounding star field is faint and there's not much in the way of deep sky objects but on the 20th Lovejoy passes 0.5 degrees east of open cluster NGC 188. With an apparent magnitude of +8.1, NGC 188 or Caldwell 1 is not one of the sky's brightest clusters but can be seen with binoculars, although much easier with telescopes. Positioned less than 5 degrees from the North Celestial Pole it holds the distinction of being the northernmost open cluster in the sky. When passing the cluster current predictions put Lovejoy at magnitude +8.5 and therefore similar in brightness.
The next major pass for Lovejoy occurs on May 29th when it passes just 1 degree west of Polaris (α UMi - mag. +2.0). It's likely to have faded to 9th magnitude by this time. As a consequence of it's high northerly declination the comet is circumpolar from virtually all the Northern Hemisphere but can't be seen from Southern latitudes.
The finder charts below show the positions of Lovejoy from March 12th to June 12th, 2015.
Comet MASTER remains well placed from southern latitudes as it heads towards closest approach to Earth and perihelion in May. During the first half of the month it's visible towards the east just before sunrise, before switching to the evening sky for the last two weeks. It's then appears fairly high in the western sky after sunset. At its brightest MASTER should be visible to the naked eye and easily seen with binoculars.
Unfortunately, from northern temperate locations the comet is not visible until September when it will be extremely faint.
Location and star chart
The comet picks up pace during May as it moves through a handful of southerly constellations. It starts the month in Sculptor on an east-southeast trajectory before crossing into Fornax on May 8th. The next stop for MASTER is Eridanus where it arrives on May 14th. Three days later it briefly passes through Caelum before moving into Lepus on May 18th. Then comes Canis Major on May 22nd and finally the comet crosses into Monoceros on May 26th where it remains until June 7th.
It's predicted that MASTER will brighten from magnitude +7.0 at the beginning of May to a peak of magnitude +5.1 on May 15th. A few days either side of this it should be visible to the naked eye and an easy binocular and small scope target. On May 18th, the comet passes less than a degree north of mag. +8.1 globular cluster M79 in Lepus. It then passes just north of mag. +5.9 open cluster M50 on May 29th. Although fading to magnitude +6.3 by months end it remains bright and easily within binocular and small scope range. Of course, comets are unpredictable and anything could happen, so keep watching!
MASTER passes closest to Earth on May 13th at 70 million kilometres or 44 million miles distant before reaching perihelion on May 23rd when it's 115 million kilometres (72 million miles) from the Sun.
The finder charts below show the positions of comet MASTER from April 17 to June 11, 2015.
Of all the planets in the Solar System the most beautiful of all is Saturn. On May 23rd the favourite planet reaches opposition and is therefore visible all night. Saturn starts the month continuing its retrograde motion in Scorpius before slowly moving into faint Libra on May 12th where it remains for the rest of the month. With a declination of –18 degrees it's better placed for Southern Hemisphere or tropical based observers where it appears higher in the sky and visible for a longer period of time.
At opposition, Saturn shines at magnitude +0.1 and is located 8.967 AU or approximately 1341 million kilometres (833.5 million miles) from Earth. Of course the spectacular rings are its most famous feature and even a small telescope will show them. They are currently wide open at a 24.4 degree tilt from our perspective. With an apparent diameter of 18.5 arc seconds and taking into account the rings, Saturn spans some 42 arc seconds across in total.
Through medium and large aperture scopes the rings are a fantastic breathtaking sight. In addition, a handful of Saturn's moons are also visible. The largest and brightest Titan shines at eight magnitude and can be seen with binoculars. In addition, small size scopes will also show other moons including Rhea, Tethys and Dione. Around opposition is a good time to look for moons of Saturn as they are also at their brightest for the year.
A good opportunity exists to spot bizarre moon Iapetus just before opposition. This world is famous for its "two-tone" colouration with one side being much darker in colour than the other. As a result, Iapetus when positioned on the western side of Saturn (when viewed from Earth) appears brighter than from the opposite side. This occurs on May 20 when Iapetus is at greatest western elongation and shines at magnitude +10.1, easily within the range of small scopes.
The chart below shows the position of Saturn in Libra at opposition. It's co-ordinates are R.A. = 15hr 59m 05s, Dec. = –18d 18h 12s.
The first three weeks of May offers an excellent opportunity for observes at Northern Hemisphere and tropical latitudes to spot elusive Mercury. During this apparition the planet is visible just after sunset low down above the west-north-western horizon. Peak altitude occurs on May 7th when greatest eastern elongation is reached. On this day, Mercury will be 21 degrees from our star and visible as a magnitude +0.2 point of light 10 or so degrees above the horizon, 45 minutes after sunset.
Due to the angle of the ecliptic, an apparition of Mercury is often better seen from one particular hemisphere. For this apparition, the Northern Hemisphere wins and this also happens to be the their most favourable evening apparition of the year.
Mercury remains an early evening object for observers located at tropical and Northern Hemisphere latitudes during the first three weeks of May. The planet is located in Taurus and is visible after sunset towards the west-northwest as soon as it's dark enough.
Mercury climbs higher in the sky each evening until it peaks on May 7th, the date of greatest eastern elongation. For example, from 52N (e.g. London, England) the fast moving planet (mag. +0.2) is positioned 11 degrees above the horizon, 45 minutes after sunset. Afterwards its altitude decreases until it's finally lost to the bright twilight sometime during the third week of the month. It should be noted that Mercury is at its brightest before elongation - it fades from magnitude -0.4 to +1.5 during the first half of May. Located a few degrees northeast of Mercury is much more brilliant Venus (mag. -4.3).
The chart below shows positions of Mercury and Venus from latitude 52N (e.g. London, England). The view will be similar from other northern temperate locations.
On May 12th, Mercury (mag. +1.0) passes 8 degrees north of orange giant star Aldebaran (α Tau - mag. +0.9) the brightest star in Taurus. The fast moving planet then reaches a stationary point on May 19th. Retrograde motion follows pulling Mercury back towards the Sun with it arriving at inferior conjunction on May 30th.
From the Southern Hemisphere the planet is not well placed for observation but may be glimpsed extremely low down above the west-northwestern horizon just after sunset at the start of the month.
Venus continues as a blazing evening object as it heads towards greatest eastern elongation of 45 degrees on June 6th. The planet is so bright that it can't be mistaken and can be spotted even before the Sun dips below the horizon. During May it brightens from magnitude -4.2 to -4.4 with its apparent size increasing from 17 to 22 arc seconds. The phase of the planet decreases from 67 to 54 degrees during the same period.
The period of visibility of Venus varies considerably depending on location. From northern temperate latitudes the planet sets almost 3.5 hours after the Sun at the start of the month, increasing to 4 hours by months end. However, much further south the planet can be seen for as little as 2 hours. On May 21st the waxing crescent Moon passes 8 degrees south of Venus and at the end of the month, Venus passes 4 degrees south of the Gemini twins, Castor (α Gem - mag. +1.6) and Pollux (β Gem - mag. +1.1).
Mars has now just a few weeks to go before reaching solar conjunction on June 14th. The "Red planet" spends the first few days of May in Aries before moving into Taurus where it remains for the rest of the month. With an apparent magnitude of only +1.5 it's not bright easily lost to the evening twilight and unlikely to be seen this month.
Jupiter is now 3 months past opposition but despite fading in brightness the planet remains a brilliant object in Cancer. The gas giant is moving direct and positioned 7 degrees southeast of beautiful binocular and small telescope open cluster M44 "The Praesepe".
Jupiter is visible as soon as it's dark enough. At the end of the month, it sets just after midnight from northern temperate latitudes but visibility is somewhat shorter for those living in the tropics and further south. The planets magnitude decreases from -2.1 to -1.9 during May with the apparent size diminishing from 38 to 35 arc seconds over the same time period.
On May 24th, the waxing crescent Moon passes 5 degrees south of Jupiter.
Saturn reaches opposition on May 23rd and is therefore visible all night as it continues its slow retrograde motion, starting the month in Scorpius before moving into faint Libra on May 12th. The favourite planet of many astronomers is now at it's stunning best with the rings wide open at a tilt of 24.4 degrees and an apparent diameter of 18.5 arc seconds. Including the rings it spans some 42 arc seconds across. The current southerly declination of Saturn means it's much better placed for Southern Hemisphere or tropical based observers.
Through telescopes, Saturn's rings are a wonderful sight and visible even in the smallest of instruments along with Titan, the largest and brightest moon of Saturn. Larger telescopes reveal subtle planet details and many of the planets other moons.
At opposition, Saturn shines at magnitude +0.1 and is positioned 8.967 AU or approximately 1341 million kilometres (833.5 million miles) from Earth. The full Moon passes 2 degrees north of Saturn on May 5th.
Uranus at magnitude +5.9 is currently located in Pisces. For the first half of May from northern temperate latitudes the planet is too down low to be seen against the bright morning twilight. However, the situation quickly improves and by months end Uranus rises over 2 hours before the Sun, therefore visible through binoculars and telescopes against the darker backdrop. Observers located further south have it even better with Uranus well placed in the early morning sky throughout the month. At the start of the May, the planet rises 2 hours before the Sun with the visibility period more than doubling by May 31st.
The waning crescent Moon passes 0.2 degrees north of Uranus on May 15th and an occultation is visible from central South America, west and central Africa (11:55 UT).
Neptune is a morning object amongst the faint stars of Aquarius, the Water Bearer or Water Carrier. The planet is better placed from tropical and southern latitudes, rising in the east some four hours before the Sun at the beginning of the month. By months end it can be seen around midnight. From Northern temperate latitudes Neptune is better seen towards the end of the month when it rises 3 hours or so before the Sun.
At magnitude +7.9, the Solar System's most distant planet is never bright enough to be visible to the naked eye but can be spotted with binoculars and small telescopes. Telescopes at medium to high magnifications reveal a featureless small blue disk that spans just 2.3 arc seconds across.
The last quarter Moon passes 4 degrees north of Neptune on May 12th.