Mercury

Mercury passes through superior conjunction on July 7th but it's not long before the rapid moving planet moves out from the Sun and into the early evening sky. During the second half of the month it re-appears after sunset low down towards the west-northwestern horizon from equatorial and southern latitudes. Observers should note that although Mercury's altitude improves slightly each subsequent evening it dims from magnitude -1.2 to -0.2 between July 15th and 31st. From northern temperate latitudes the planet struggles against the lengthy summer twilight making observations almost impossible.

There are a couple of interesting conjunctions coming up. On July 16th, Mercury passes 0.5 degrees north of much brighter Venus, with Mercury (mag. -1.1) 13 times fainter than its mag. -3.9 neighbour. However, this is a challenging event to observe since both planets remain low down. For example, from latitude 35S (approx. equal to Sydney, Cape Town and Santiago) Mercury and Venus appear just 4 degrees above the horizon, 30 minutes after sunset. Binoculars are recommended and safe-viewing techniques should be followed. Ensure that the Sun is below the horizon before scanning the sky. Two weeks later on July 30th, Mercury (mag. -0.2) passes 0.3 degrees north of Regulus (mag +1.4) the brightest star in Leo.

Of all multiple star systems consisting of at least three stars, perhaps the finest and most celebrated of all is Epsilon (ε Lyr) Lyrae, better known as "The Double Double." What is great about this star system is that it offers something for everyone, from the naked-eye observer to those with the largest of amateur telescopes.

Epsilon Lyrae (ESO Digitized Survey)

NGC 6231 is a bright open cluster of approx. 120 stars spread over 15 arc minutes of sky in Scorpius. With a combined magnitude of +2.6 the group is visible to the naked eye and a stunning object through binoculars and telescopes. At its heart are numerous hot luminous fifth and sixth magnitude blue-white type B supergiants. They appear similar to a smaller version of M45, the famous Pleiades cluster in Taurus.

NGC 6231 is located half a degree north of bright star Zeta Scorpii whose Bayer designation is shared by zeta1 Scorpii (ζ1 Sco - mag. +4.7) and zeta2 Scorpii (ζ2 Sco - mag. +3.6). The two stars are separated by 7 arc minutes but this is no physical double star, just a line of sight effect. Zeta2 is much closer at 155 light-years while zeta1 - an outlying member of NGC 6231 - lies 5,700 light-years distant. NGC 6231 is also known as the Northern Jewel Box.

NGC 6231 - Open Cluster (credit - Australian Astronomical Observatory / David Malin)

Albireo (β Cyg) is a showpiece double star and one of the great small telescope night sky objects. To the unaided eye it's the fifth brightest star in Cygnus (combined mag. +2.9) and the lone star that marks the head of "the Swan" constellation. When viewed through a small telescope or even good 10x50 binoculars, Albireo is split into two components, a mag. +3.1 primary (Albireo A) and a mag. +5.1 secondary (Albireo B). These stars are separated by a generous 34.3 arc seconds but the most pleasing aspect of this grouping and what makes it such a special object is its beautiful colour contrast, a brilliant yellowish primary coupled with a soft blue secondary.

Location

Cygnus is one of the most recognizable constellations during the Northern Hemisphere summer and autumn months. It represents a Swan flying down the plane of the Milky Way. Containing many bright stars, positioned at the heart of the constellation is a prominent asterism in the shape of a large cross. Consequently it's often referred to as the Northern Cross. At the northern end of the cross is Deneb (α Cyg); a blue-white supergiant star (mag. +1.3) and the brightest star in the constellation. Deneb marks the "tail" of the Swan and located at the opposite side of the cross, Albireo, marks the "head" of the Swan.

Vulpecula
Vulpeculae
Vul
The Fox / The Little Fox

Introduction

Vulpecula is a small, faint constellation located in the northern section of the sky. Strangely, it was not one of the original 48 constellations created by 2nd century astronomer Ptolemy, even though the pattern of stars were clearly visible to him and other ancient Greeks and Romans.

The constellation we know today was created by Johannes Hevelius. He included it in his influential 56 page star atlas, Firmamentum Sobiescianum, which was published posthumously in 1690. Originally it was known by two names, Vulpecula cum anser and Vulpecula et Anser. The first means the little fox with the goose and the second the little fox and the goose. In his original illustration, Hevelius depicted an unfortunate goose carried in the jaws of a fox. Later the constellation was divided into two separate parts, Vulpecula and Anser. It was then re-merged into a single entity - simply named Vulpecula - by the International Astronomical Union (IAU) in the 20th century. The only remains of the goose is the constellation's brightest star, Anser (α Vul).

Locating the area of the sky where Vulpecula lies is easy; it's wedged between Cygnus and Sagitta with the western half located roughly in the middle of the well observed Summer triangle (an asterism consisting of the bright stars Deneb, Vega and Altair). For deep sky observers, Vulpecula contains the superb Dumbbell Nebula, a famous coathanger shaped open cluster and a few other open clusters. At 288 square degrees, it's the 55th largest constellation in the sky.

IC 2602 is a prominent open cluster in the southern constellation of Carina that was discovered by Abbe Lacaille in 1751 from South Africa. It contains about 60 stars spread across 50 arc minutes and is easily visible to the naked eye. The brightest member is blue-white Theta Carinae (θ Car) which shines at mag. +2.74. Of the remaining constituents all are of fifth magnitude or fainter. When seen through binoculars and small scopes, IC 2602 is a stunning object and a superb example of its type.

IC 2602 (credit - Roberto Mura)

Hercules
Herculis
Her
The Strongman

Introduction

The constellation of Hercules is one of the original 48 constellations plotted by 2nd century astronomer Ptolemy and remains today as one of the modern 88 constellations. Hercules is the 5th largest constellation and spans an impressive 1,225 square degrees of sky. However, despite its large apparent size it's rather faint. Although easily traceable under dark skies, the constellation can become elusive with just a hint of light pollution or when viewed under a moonlit sky.

The centrepiece of Hercules is a trapezoid shaped asterism commonly known as the Keystone. The four stars of the Keystone are Eta Herculis, Zeta Herculis, Epsilon Herculis and Pi Herculis. They are all between magnitudes 3 and 4 in brightness. The brightest of the four, Zeta Herculis, shines at magnitude + 2.81 and is the second brightest star in the constellation. Along with marginally brighter Kornephoros (Beta Herculis) these are the only two stars in Hercules above magnitude +3.0.

For deep sky enthusiasts Hercules contains a sprinkle of globular clusters, challenging planetary nebulae and a host of faint galaxies.

NGC 663, mag. +7.1, is a young open cluster that's one of a number of bright clusters that can be seen with binoculars in the constellation of Cassiopeia. It contains at least 80 stars visible in amateur telescopes spread over a diameter of 16 arc minutes. A 100mm (4-inch) scope reveals a bright rich grouping immersed in a hazy glow with many stars resolvable. NGC 663 is striking in larger scopes appearing reasonably concentrated towards the centre with dozens of stars spread across the cluster face. Double star Struve 152 is a cluster member.

NGC 663 (credit - Hunter Wilson)

Mars and Saturn are currently visible as soon as it's dark enough and remain so until the early hours of the morning. The two planets are positioned about 15 degrees apart in their respective constellations of Libra and Ophiuchus. Due to their southern declinations they are better placed from tropical and southern latitudes, appearing higher in the sky with a longer visibility period than at mid-northern latitudes. This rich area of sky also contains many deep sky objects and bright stars, including first magnitude red supergiant Antares (α Sco - mag. +1.0). Of the three objects Mars (mag. -1.7) is the brightest followed by Saturn (mag. +0.1) then Antares.

Some pleasant viewing opportunities occur between June 16th to 19th when the Moon is also in the same region of sky. On June 17th, it passes 7 degrees north of Mars and two days later 3 degrees north of Saturn. The image below shows the view just before midnight from London, England. From other mid-latitude northern locations the scene will be similar to that shown.

Comet PanSTARRS (C/2013 X1) is visible with binoculars in the evening sky during June from southern and tropical latitudes. At the beginning of the month the comet was rising in the southeast before midnight local time. By months end it can be seen just after sunset. Although probably remaining beyond naked eye visibility it's predicted to reach about mag. +6.0 towards the end of the month and therefore an easy binocular object. Indeed throughout June, PanSTARRS should be at least as bright as mag. +6.5. However comets are unpredictable and anything can happen, so keep watching!

Due to its southerly declination, those living at mid-northern latitudes aren't so lucky. Observers may be able to spot the comet low down in the southern sky just before morning twilight during the first half of the month. After that it will no longer be visible.

Comet PanSTARRS (C/2013 X1)as imaged on May 11, 2016 (credit - José J. Chambó / cometografia.es)

Jupiter despite fading remains visible as a beautiful evening object towards the west just after sunset. The planet can't be mistaken; at mag. -2.0 it dominates its surrounding region of sky. No other currently visible celestial objects apart from the Sun and Moon are brighter than Jupiter although Mars is only marginally fainter. However, it's impossible to confuse the two planets. Mars is visible towards the east on the opposite side of the sky and is deep orange in colour compared to brilliant white Jupiter.

Moon and Jupiter early evening June 11 from New York City (credit - stellarium/freestarcharts)

Ursa Minor
Ursa Minoris
UMi
The Little Bear

Introduction

Ursa Minor is a medium size constellation located in the far northern reaches of the sky. Also known as the Little Bear, its main group of stars resemble a smaller version of the Great Bear of Ursa Major. Greek astronomer Thales first mentioned the constellation, around 600 BC, after realising it could be used as a better guide to finding true north than Ursa Major. Over the years it has been visualised as many things, including a dog's tail revolving its tip and a bunch of jewels.

Ursa Minor has been important for navigation since it contains the North Celestial Pole (NCP). Currently, the constellation's brightest star Polaris (mag. +1.97) is only three quarters of a degree from the NCP, thereby providing a convenient marker. Polaris is slowly edging nearer and on March 24, 2100 it will be less than half a degree removed. After that it gradually moves away.

Like Ursa Major, the main seven stars of Ursa Minor form the handle of a ladle. The bowl contains second magnitude Kochab (β UMi) and third magnitude Pherkad (γ UMi), which are collectively known as the guardians of the pole. The remaining members of the group are fainter, down to fifth magnitude, but do provide a useful sky darkness check scale. On good nights all seven stars can be seen with the naked eye.

Variable star R Aquilae in the constellation Aquila is now towards the bright end of its range and currently easily visible with binoculars and small scopes. The star is a Mira type that normally fluctuates between magnitudes +5.5 and +12.0 over a period of 284 days. At it's brightest it can be glimpsed faintly with the naked eye. At it's faintest a minimum 80mm (3.1-inch) scope is required.

R Aql finder chart (credit - freestarcharts)

R Aql finder chart - pdf format - (credit - freestarcharts)

Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star" most of the time it shines at magnitude +2.1 but every two days, 20 hours and 49 minutes the star suddenly dips in brightness to magnitude +3.4, remaining dim for about 10 hours before returning to its original state.

Why the change in brightness? The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary but this results in a very small dip in brightness that can only be detected by those with access to photo-electrical equipment.

Algol System (credit - Dept. of Physics and Astronomy - Univ. of Tennessee at Knoxville)

Mercury

Mercury reaches greatest elongation on June 5th when it's positioned 24.2 degrees west of the Sun. Despite this at northern latitudes the angle of the ecliptic is unfavourable and the planet will be challenging to spot low down above the eastern horizon. However it's a different story from the Southern Hemisphere where elusive Mercury puts on a respectable morning show for the first three weeks of the month. During week one it rises more than two hours before the Sun and can be seen 10 degrees above the east-northeastern horizon an hour before sunrise. After that Mercury slips back towards the Sun until it's finally lost to the bright twilight during the last week of June. It should be noted that the planet gains in brightness from mag. +0.8 to -1.0 during the visibility period.

On June 3rd, the thin waning crescent Moon passes 0.7 degrees south of Mercury (mag. +0.5) with an occultation visible from southern Africa and Madagascar (9:47 UT).

Venus

Venus reaches superior conjunction on June 6th. Since the planet is currently located on the far side of the Sun it's not suitably placed for observation. Indeed from June 5th to June 7th, Venus passes directly behind the Sun as seen from Earth. This "occultation" lasts some 46 hours and for its duration no Earth based instrument will be able to detect the planet.

At conjunction Venus and the Earth are separated by 1.74 AU (260 million kilometers or 161 million miles).

Saturn reaches opposition in Ophiuchus on June 3rd. On this day the planet is visible all night long and at its best for the year. With a declination of -20.5 degrees it's much better placed from southern and tropical locations. For example, the planet reaches at maximum altitude of 77 degrees and is visible for over 13 hours from Sydney, Australia. Whereas from New York City, it climbs just 29 degrees high, visibility only 9 hours.

The surrounding region of sky also contains Mars (mag. -2.0) about 15 degrees to the west and first magnitude red supergiant star Antares (α Sco - mag. +1.0) approx. 6 degrees southwest of Saturn. Of the three objects Mars is easily the brightest followed by Saturn then Antares. Saturn reaches its highest point in the sky at around midnight local time.

Saturn imaged by the Hubble Space Telescope (credit - NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

PanSTARRS (C/2013 X1) is currently the brightest comet in the sky and can be seen with binoculars and small telescopes in early morning. The comet is currently approaching Earth and will continue to brighten slightly, peaking at mag. +6.0 when closest approach is reached at the end of June. It's better placed from southern and equatorial latitudes where it appears high in the sky than from northern temperate locations where it always keeps low down.

Comet PanSTARRS (C/2013 X1)as imaged on May 11, 2016 (credit - José J. Chambó / cometografia.es)

Now is a great time for observers of Mars as the famous "Red planet" reaches opposition on May 22nd in Scorpius. On this day it peaks at mag. -2.1 and for a short time rivals the normally more brilliant Jupiter in brightness. However although visible all night long, due to its southern declination Mars is much better placed from Southern Hemisphere and tropical latitudes rather than northern temperate locations. For example on May 22nd from London, England the planet rises at 20:55 and sets at 05:02, a visibility period of about 8 hours. Whereas from Sydney, Australia it rises at 16:52 and sets at 07:00 hence visible for over 14 hours. In addition, Mars reaches a maximum altitude of just 17 degrees above the southern horizon from London. For comparison from Sydney it peaks at 77 degrees above the horizon, effectively appearing overhead.

Jupiter although fading remains a beautiful evening object in the constellation of Leo. After sunset the giant planet can be seen high in the sky above the south-western (Northern Hemisphere) or north-eastern horizon (Southern Hemisphere). It's impossible to miss Jupiter, with an apparent magnitude of -2.2 the planet is more than twice as bright as Sirius the brightest night time star. It's also brighter than all other planets except for Venus, although at the moment slightly fainter Mars does rival Jupiter in brightness. However, it's impossible to confuse the two planets. Mars rises just after sunset and is a deep orange/red in colour compared to brilliant white Jupiter which is high in the sky as soon as it's dark enough. Both planets dominate their surrounding region of sky.

On the evenings of May 14th and 15th a lovely pairing occurs when the waxing gibbous Moon passes just a couple of degrees south of Jupiter.

On May 9th a transit of Mercury occurs when the planet crosses the face of the Sun for the first since 2006. The event is visible (at least partially) from most parts of the World. It begins at 11:12 UT, ends at 18:42 UT with the midpoint occurring at 14:58 UT. The transit lasts for 7.5 hours in total and observers will notice a tiny 10 arc second diameter dark disk moving slowly across the solar face.

Mercury transit of November 8, 2006 (credit - Eric Kounce)

The annual Eta Aquariids meteor shower peaks on the morning of May 6th. For Southern Hemisphere observers this is the best meteor shower of the year. In addition, prospects are good as the New Moon won't interfere during peak activity and up to 55 meteors per hour are predicted.

Parent Comet

The parent body for the Eta Aquariids meteor shower is Halley's comet (1P/Halley). This isn't the only annual shower associated with the famous comet, the October Orionids also originate from the same source. Although Halley has now left the inner Solar System and won't return until 2061 it's worth remembering that every Eta Aquariids meteor is actually a small part of the famous comet burning up in the Earth's atmosphere.

Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star" most of the time it shines at magnitude +2.1 but every two days, 20 hours and 49 minutes the star suddenly dips in brightness to magnitude +3.4, remaining dim for about 10 hours before returning to its original state.

Why the change in brightness? The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary but this results in a very small dip in brightness that can only be detected by those with access to photo-electrical equipment.

Algol System (credit - Dept. of Physics and Astronomy - Univ. of Tennessee at Knoxville)

Mercury

From equatorial and southern temperate latitudes Mercury can be spotted during the last few days of the month as an early morning object low down above the east-northeastern horizon just before sunrise. From northern temperate latitudes the planet is swamped by the lengthening twilight and is unlikely to be seen.

On May 9th a rare event occurs when Mercury transits the Sun and appears to move across the solar disk. The transit begins at 11:12 UT, ends at 18:42 UT with the midpoint occurring at 14:58 UT. Observers will notice a tiny 10 arc second diameter disk silhouetted against the solar disk.

Mercury transit of November 8, 2006 (credit - Eric Kounce)

The annual Lyrids meteor shower peaks during the night of April 21st/22nd but unfortunately the full Moon will interfere significantly. Normally you would expect to see up to 20 meteors per hour under ideal conditions, however due to the presence of the Moon only the brightest few meteors will be visible. It is still worth looking outside as the Lyrids do occasionally produce brilliant fireballs that streak through the sky and cast shadows as they disintegrate in the Earth's atmosphere.

View early hours on the morning of April 22, 2016 from London, England (credit - stellarium/freestarcharts)

Jupiter is now past opposition but remains a stunning evening object in the constellation of Leo. After sunset the giant planet can be seen above the southeastern horizon (Northern Hemisphere) / northeastern horizon (Southern Hemisphere). It's not possible to miss Jupiter, with an apparent magnitude of -2.4 the planet is 2.5x brighter than Sirius and brighter than all other planets except for Venus. It dominates the surrounding region of sky.

On the evenings of April 17th and 18th a lovely pairing occurs when the waxing gibbous Moon passes just a few degrees south of the planet.

Moon and Jupiter 45 minutes after sunset from London, England on April 17, 2016 (credit - stellarium)

Periodic comet 252P/LINEAR which has an orbital period of 5.33 years has now just past perihelion - closest point to the Sun - and should remain visible with binoculars and small scopes in the early morning April skies. Although only discovered at the turn of the century this comet has surprised astronomers by its brightness, over 100x more than originally predicted. On March 21st it passed just 0.036 A.U. (14 Moon distances) from the Earth and shone at mag. +3.9 and therefore visible to the naked eye.

Comet 252P/LINEAR on March 18, 2016 (credit - Gerald Rhemann / Namibia)

Mercury reaches greatest elongation east (GEE) on April 18th when it's positioned 19.9 degrees from the Sun. The nearest planet to the Sun will be visible during April low down above the west-northwestern horizon shortly after sunset. This months apparition offers the best opportunity (evening) for observers at northern latitudes to spot the elusive planet this year. From equatorial regions Mercury is also visible during April but from mid-southern latitudes unfortunately not.

Mercury as seen by the Messenger space probe (credit - NASA)

Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star" most of the time it shines at magnitude +2.1 but every two days, 20 hours and 49 minutes the star suddenly dips in brightness to magnitude +3.4, remaining dim for about 10 hours before returning to its original state.

Why the change in brightness? The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary but this results in a very small dip in brightness that can only be detected by those with access to photoelectrical equipment.

Algol System (credit - Dept. of Physics and Astronomy - Univ. of Tennessee at Knoxville)

Mercury

Mercury is visible as an evening object for observers at northern and equatorial latitudes during April (apart from the few days at the start and end of the month). For this apparition the planet can be seen low down above the west-northwestern horizon just after sunset. The peak altitude occurs on April 18th when greatest elongation east (GEE) is reached. On this day, from London for example, the planet will be visible as a mag. -0.1 point of light 10 degrees above the horizon, 45 minutes after sunset. Observers should also note that Mercury is at its brightest at the start of the month and before GEE occurs. It decreases from mag. -1.4 to +2.1 during the visibility period.

On April 8th the thin waxing crescent Moon passes 5 degrees south of Mercury, aiding in locating the planet.

Thin crescent Moon and Mercury just after sunset from mid-northern temperate latitudes on April 8, 2016 (credit - stellarium)

Mars and Saturn are currently positioned only a few degrees apart in their respective southern constellations of Scorpius and Ophiuchus. From March 28th to 30th some nice visual and photographic opportunities occur when the waning gibbous Moon is also positioned close by.

Currently the two planets are better seen from tropical and southern locations where they rise earlier in the evening and appear higher in the sky than for those living further north. For example, from Cape Town, South Africa or Sydney, Australia the planets are visible well before midnight but from locations such as London, England or New York, USA they don't rise until a few hours later.

Moon, Mars and Saturn as seen a couple of hours before sunrise from London, England on March 29, 2016 (credit - stellarium)

Jupiter is now just past a few days past opposition and remains a brilliant object moving retrograde in southeastern Leo. The giant planet with a diameter 11 times that of the Earth rises in the east just before sunset remaining visible for most of the night. Now at its best for the year the "King of the planets" is unmistakable (mag. -2.5) and much brighter than all night time stars.

On March 21st a nice visual event occurs when the almost full Moon passes 2 degrees south of Jupiter in the evening sky.

Jupiter and the Moon as seen from New York, USA in early evening on March 21, 2016 (credit - freestarcharts)

A total solar eclipse visible from Indonesia and the central Pacific region takes place on March 9, 2016. On this occasion the narrow totality band starts at sunrise over Sumatra before passing through Bangka Island, Palau Belitung, Central Kalimantan, Central Sulawesi, North Maluku, Woleai Atoll and ending in the Pacific Ocean north of Hawaii. A partial eclipse is visible from large parts of Southeast Asia, Northern Australia, Papua New Guinea, Hawaii, China and Alaska. Readers should be aware that since the shadow crosses the International Date Line for locations such as Alaska and Hawaii the eclipse takes place on March 8th.

A total solar eclipse occurs when the Moon passes directly between the Earth and the Sun, hence the Sun's disk is obscured as seen from the ground. Total eclipses are only possible due to a large slice of nature's luck. By sheer coincidence the Sun is about 400 times larger in size than the Moon but also 400 times more distance resulting in both objects appearing about the same size in the sky. However, it should be noted that due to distance variations the apparent sizes of the Sun and Moon do show small variations and at times the Moon will appear slightly larger in the sky than the Sun and vice-versa. A total solar eclipse occurs when the Moon's apparent diameter is large enough to completely cover the Sun and therefore block all direct sunlight, in the process turning day into darkness.

Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star" most of the time it shines at magnitude +2.1 but every two days, 20 hours and 49 minutes the star suddenly dips in brightness to magnitude +3.4, remaining dim for about 10 hours before returning to its original state.

Why the change in brightness? The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary but this results in a very small dip in brightness that can only be detected by those with access to photoelectrical equipment.

Algol System (credit - Dept. of Physics and Astronomy - Univ. of Tennessee at Knoxville)

Mercury

During the first week of March from equatorial and southern regions Mercury can be seen low down above the eastern horizon just before sunrise. Also visible six degrees above the planet is much more brilliant Venus which acts as a good marker. For comparison, Mercury shines about mag. -0.4 while Venus is at mag. -3.8, a difference of 22x.

On March 8th the very thin waning crescent Moon passes 4 degrees north of Mercury although spotting the planet with the naked eye is likely difficult and binoculars will probably be necessary. After that Mercury continues to draw into the Sun before reaching superior conjunction on March 23rd.

From northern temperate latitudes the planet is not suitable placed for observation throughout the month.

Morning apparition of Mercury as seen from latitude 35S - 45 minutes before sunrise (credit - freestarcharts)

Jupiter is currently a brilliant object moving retrograde in southeastern Leo. The giant planet which has a diameter 11 times that of the Earth rises in the east just after sunset and remains visible for the rest of the night. With only two weeks to go until opposition it's now the best time of year to view the "King of the planets". At magnitude -2.5 it's unmistakable and much brighter than any other night-time star.

On the evening of February 23rd and the morning of February 24th a nice visual and imaging opportunity occurs when the waning gibbous Moon (almost full) passes less than 2 degrees south of Jupiter.

Jupiter and the Moon as seen from New York in early evening on February 23, 2016 (credit - freestarcharts)

Despite moving away from Earth as it heads towards the outer reaches of the Solar System comet Catalina remains well placed from Northern Hemisphere and tropical locations during February. At the start of the month the comet shone at magnitude +6.9 and beyond naked eye visibility but easily within binocular range. Unless something now dramatic happens it's expected to fade by another two magnitudes by months end, becoming increasingly difficult to spot with binoculars. At this level of brightness a small size telescope - preferably larger - is recommended for observing. From mid southern locations Catalina can no longer be seen.

Comet Catalina (credit - Ian Sharp/SSO)

Sky Highlights - July 2017

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for July

Meteor Shower
Southern Delta Aquariids (Aquarids) meteor shower peaks on July 29

Northern Hemisphere
Evening
West:- Mercury (mag. -0.5 to +0.3) (second half of month)
Southwest:- Jupiter (mag. -2.0)
South:- Saturn (mag. +0.2)
Midnight
West:- Jupiter
South:- Saturn
East:- Neptune (mag. +7.8)
Morning
Southwest:- Saturn
South:- Neptune
Southeast:- Uranus (mag. +5.8)
East:- Venus (mag. -4.1)

Southern Hemisphere
Evening
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
Midnight
West:- Jupiter
North:- Saturn
East:- Neptune
Morning
West:- Saturn
North:- Neptune
Northeast:- Venus, Uranus

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

Guides / Star Charts

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