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Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

It's July - and the nights in the northern hemisphere are still on the light side as far as deep sky observations go, but this is normally one of the more pleasant times of the year to be observing outside at night. Those in the southern hemisphere will be experiencing just the opposite, having just emerged from the midwinter solstice.  With Mars at opposition along with a Total Lunar Eclipse on the smae night, Jupiter and Saturn well-placed for early evening observations, a reasonably bright telescopic comet  - wherever you find yourself in the world, there’s plenty to see… 

 

The Solar System

 

 

The Moon

 

 

 

The Moon starts July in Capricornus, fairly low in the southern ecliptic from a northern hemispherical perspective, at a few days past Full. Rising early in the morning on the 1st, the Moon sits around 4 of a degrees north of The prominent Mars. Being so close to Full Moon, naturally, this is not the best time for deep sky observations, or imaging faint objects without significantly narrowband filtration.

 

 

 

The Moon reaches Last Quarter on the 6th, while residing in The non-zodiacal constellation of Cetus.

 

 

 

The Moon reaches New as it joins the Sun in Gemini on the 13th, after which it becomes an evening target. On the evening of the 14th, it may be possible to observe the very slim New Crescent Moon, sitting about 2 1/3 degrees to the west of Mercury, pin the Leo/Cancer borders, just after sunset - though the window for finding the pair is very narrow and binoculars or a telescope will be needed to do so. A less challenging pairing can be seen the following evening, when observers can pick out the very slim Crescent Moon alongside Venus, just after sundown, with the two bodies separated by about 5 degrees (when viewed from Europe), in Leo. 

 

 

The Moon, Mercury and Venus, sunset, 15th July.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

The Moon reaches First Quarter in Virgo on the 19th and can be found alongside Jupiter in Libra the following evening, with the Moon 5 1/2 degrees north west of the prominent planet. 

 The Moon becomes Full on the 27th, while in Capricornus, which coincides with an encounter with the Mars, itself at opposition on this day, and a Total Lunar Eclipse. This eclipse begins its Penumbral phase at around 6.17pm BST. The Moon rises from many European and African locations after the darker Umbral phase has begun a little after an hour and twenty minutes later. 

 

 

Eclipsing Moon and Mars rising, July 27th 10pm (BST).  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

For UK observers and those in the western parts of Europe and Africa, the Moon will rise at full Umbral phase - at the darkest part of the eclipse. It should be fascinating to watch the Moon reemergence from the Earth's shadow, the higher it gets in the sky. 


 Moon emerging from the Umbral phase of the eclipse, 10.30pm 27th July.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

The full Umbral phase starts to end at a little before 10.15 pm BST, after which the Penumbral part of the Earth's shadow - the refracted light passing through the Earth's atmosphere - will reveal itself. The Umbral part of the eclipse will end at 11.18pm BST, with the Penumbral phase coming to its conclusion at just before 12.28am on the early morning of the 28th.   If the weather is kind, this should be a spectacular evening for astronomical observations - with the added bonus of Mars at opposition just a few degrees to the south. 

 After the eclipse is over, the Full Moon will reveal itself in full. Again, as was the case in early July, this is not the ideal time for deep sky observations and imaging. 

 The Moon ends July at Waxing Gibbous phase in Aquarius, just a little under 5 degrees to the south of Neptune. 

 

 Mercury

 

Mercury begins the month at +0.0 mag, presenting a 59.5% illuminated, 6.7 arc second diameter disk. It stands a little under 11 degrees high at sundown (from latitude 51 degrees N), and is thus well-placed for observation from northern parts - though those in the equatorial parts of the planet will see it better, as it is now separated from the Sun by 24 degrees. 

 

 

 Mercury's phase, sunset, 1st July.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


Mercury reaches its greatest eastern elongation in the 12th, separated from the Sun by 26 1/3 degrees - though is still a rather disappointing +0.6 mag, 8.2 arc second diameter target, showing a 40% phase. Sitting in Cancer, Mercury is reasonably positioned in the sky at sunset from a northern temperate perspective - at a little under 9 degrees high (from latitude 51 degrees N). However, as is always the case, those in the tropics will see the planet much higher in the evening sky. 

After this point, Mercury begins its inevitable dive back towards the Sun and will appear to sink rapidly in altitude at sunset from a northern hemisphere perspective. This is due to the fact our parent star has now coasted over the very highest northern part of the ecliptic in late June, at the summer solstice and is itself losing altitude in the sky from a northern hemispherical perspective. Mercury itself is swinging towards us at the same time, foreshortening its phase, with an attendant drop in brightness.

 By the end of June the innermost planet is a rather pitiful +2.5 mag, showing a 10.9 arc second diameter, 10% illuminated disk. Mercury at this point, while separated from the Sun by 15 1/2 degrees, now sets practically in line with the Sun (from the temperate northern hemisphere), making it pretty much unobservable. 

 

 Venus

 

At the beginning of the month, Venus has just crossed into Leo from Cancer and is displaying brightness of -4.1 mag. Presenting a 15.8 arc second, 69% illuminated disk, the planet stands 18 degrees high in the west at sunset.

 

 Venus' phase, sunset, 1st July.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

As Venus has passed over the highest northern point in the ecliptic, it is slowly losing altitude for those of us in the northern hemisphere - though it is still some way off greatest eastern elongation from the Sun (this occurs in mid-August).  Concurrently, it is gaining altitude for those in the southern hemisphere and equatorial regions of the planet. It is also increasing in angular size and brightness as it draws closer to Earth - though again, this is a gradual process. 

 By mid-month, Venus is still found in Leo and while it hasn't increased in brightness, it has swelled somewhat to 17.6 arc seconds diameter and its phase has decreased to 64%. It now stands 15 2/3 degrees high, almost due west at sunset (from latitude 51 degrees N) on the 15th. Venus is joined in Leo by the very new crescent Moon on this particular evening, the two separated by 5 degrees as the Sun sets over Europe and Africa. 

 By late July, Venus is found on the Virgo/Leo borders and increased brightness to -4.2 mag. Presenting a 20.4 arc second, 57% illuminated disk, the planet stands just under 13 degrees high in the west at sunset. 

 

Mars

 

July brings as the long-awaited opposition of Mars. The Red Planet will be at its closest point to Earth since the opposition of 2003. On the 1st July Mars can be found in Capricornus, shining at a striking -2.2 mag and is now 20.9 arc seconds across. The planet rises at 11.19pm (BST), alongside the waning gibbous Moon on this evening - the two forming a striking pair in the sky. 

 

 

 Mars' growth in angular size over the last few months, with Jupiter and Saturn to same scale.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Mars is now a serious target for observation in any telescope and will display continental-sized surface features in practically any telescope. The use of filters, particularly the #23A Light Red filter, will help isolate these darker parts of the Martian disk. An #82a Light Blue will also help Mars' polar caps stand out.  This filter will definitely be of use as during this particular Martian apparition, Mars' smaller southern polar cap will be turned towards us. This is more difficult to spot than the larger northern cap, which was turned towards us in the first few months of 2018, and the adjacent Hellas basin, which often fills with mist and clouds, can often appear very bright and is easily mistaken for the southern polar cap. Observations at different frequencies bring certain features to the fore and make their identification easier and more precise. 

 By mid-July, Mars has brightened to a brilliant -2.6 magnitude and is now the brightest object in the sky bar the Sun, Moon and Venus. By this point in time the planet measures 23.2 arc seconds across and rises around an hour earlier than it did at the beginning of the month. 

 Mars reaches opposition on the 27th, when it will have brightened yet further to a dazzling -2.8 magnitude and display a 24.2 arc second diameter disk. As previously mentioned, Mars will de at its closest to Earth for 15 years - and will be found some 57.8 million km away from us on opposition night. 2003's opposition was slightly closer at 56 million km, but Mars at this current opposition will appear pretty much as brilliant - though 2003's appeared fractionally larger in term of angular size at 25.1 arc seconds and peaked at -2.9 mag brightness. These peaks in brightness and angular size are down to Mars' rather eccentric orbit, which lead to 15-17 year cycle of peak oppositions. Those readers who have been observing the sky for years will no-doubt remember 2003's prominent Martian apparition, but also the September 1988 opposition, where Mars appeared practically on the celestial equator in Pisces. Both of these oppositions had Mars appearing higher in the sky from a northern hemisphere perspective, at just under 23 and 36 1/2 degrees high at transit point (from 51 degrees N). By comparison, Mars will peak at just over 13 degrees high in the south on opposition night (again, from 51 degrees N). Subsequently, this opposition definitely favours the Southern Hemisphere observation. Indeed, the current 15-17 year opposition peak cycle is heavily biased towards Mars appearing in the southern celestial hemisphere - such is the nature of this particular epoch of solar system dynamics. But make the most of this one, as the next nearest Martian opposition won't be until 2035. However, there will be plenty of oppositions between now and then - they just won't be quite as spectacular as this present one. The next two, those of October 2020 and December 2022 will be appear much higher in the sky from a northern hemisphere observers' perspective. Naturally, at present, being in the southern celestial hemisphere, Mars will be best seen the further south on Earth you are, but it will be fascinating to observe or image, wherever you are. 

 

 Mars on opposition night, with its moons, Phobos and Deimos.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Mars ends July, still at -2.8 mag, displaying a 24.3 arc second diameter disk. It rises at just before 9.15pm (BST) and sets the following morning at 4.30am. As demonstrated in the size comparison illustration above, Mars will remain at very reasonable diameter for another couple of weeks past opposition, but by the end of August will have started to noticeably diminish in size.  Strike while the iron's hot when it comes to Martian observation - enjoy it while you can.

 

 Jupiter

 

At the beginning of the month, Jupiter is a -2.3 mag target in Libra and displays a disk some 41.3 arc seconds across. The planet will stand just under 24 degrees high as it transits, which will occur at 9.06pm (BST, from 51 degrees N).

Jupiter reaches the end of its retrograde path in the sky for this year in early/mid July. Having returned to prograde direction - west to east within the ecliptic - the planet will begin to sink further south and will gently lose altitude from a northern hemisphere perspective. 

 Mid-month finds Jupiter having faded fractionally to -2.2 and now presenting a 39.7 arc second diameter disk. Jupiter rises at just before 3.25pm, transiting around 8.11pm (BST, from 51 degrees N), when the planet will be 23 2/3 degrees high in the south. 

Jupiter GRS and Europa Transit, 11pm (BST) 15th July.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

The 31st sees Jupiter having contracted a fraction to 37.9 arc seconds across and as a result has faded a tad to -2.1 magnitude. The planet now rises at just after 2.26pm (BST) and transits at 7.10pm, when it will stand just under 23 1/2 degrees high in the south (from 51 degrees N).

 

Saturn

 

Early July finds Saturn just past opposition and excellently placed for observation in the equatorial and southern reaches of our planet. For those of us further north, the separation of planet from horizon poses a challenge in terms of observation, but high speed imaging will help ride out seeing conditions for those of us in the northern hemisphere somewhat - synthesising much higher resolution images than would ever possibly be observed through a telescope, even in the most clement of atmospheric conditions. Equally viable, if you have the aperture of telescope to use successfully, would be the use of heavy filtration for visual observations - particularly the harsh Deep Red #29 filter. This attenuates the worst excesses of atmospheric jitter and can really make a difference when attempting to discern detail on the brighter planets when they are closer to the horizon. Wherever you find yourself in the world, the jewel-like Saturn should be number one on your observing list this month and for some time to follow. 

 The 1st finds Saturn at +0.0 magnitude in Sagittarius, some 18.4 arc seconds in diameter. The planet rises at 8.44 pm (BST) and transits at a little before 1am the following morning. 

 By mid-month, Saturn has faded fractionally at +0.1 mag and now presents an 18.3 arc second diameter disk. 

Saturn and major moons, 11pm (BST), 15th July.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

By the month's end, Saturn is now +0.2 mag and 18 arc seconds across. It will now rise at 6.38pm and transits at 10.37, when it will stand a little over 16 degrees high in the south (from 51 degrees N, times again BST). 

 

Uranus and Neptune

 

July finds both the outer planets as morning objects. Of the two, Neptune rises earlier, being further west in the ecliptic (in Aquarius) than Uranus, (itself a resident of Aries). Neptune is always the more difficult of the two outer gas giants and will need a telescope of reasonable power to resolve it into a disk, being +7.8 mag and just 2.3 arc seconds diameter currently. The waning gibbous Moon will pass around 3 1/4 degrees south of the planet on the morning of July 4th, giving observers a guide to the location of the planet in the sky (though scattered moonlight may make positive identification of the fainter world tricky). 

 

 Uranus and Neptune's positions, 15th July 2018.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Neptune will transit just before sunrise from mid northern latitudes around mid-month, being around 30 degrees high in the sky then (from 51 degrees N).

 Uranus is always the easier target, but is a little closer to the Sun, so rises later than its neighbour. At +5.8 mag and 3.5 arc seconds diameter, Uranus is much easier to find and identify - being technically a naked eye target. Normally however, you'll still need binoculars of reasonable power and aperture to make a positive identification. On the morning of the 7th and 8th, the waning crescent Moon can be found respectively about 8 degrees to the SW and SE of Uranus, providing a handy hint to the planet's location in the sky. 

 

 

Comets

 

 While readers in the temperate northern hemisphere have lost comet PanSTARRS C/2016 M1 from view as it continues its journey south, those in the southern hemisphere and equatorial regions of our planet should still be able to follow its track through Arc, Norma and Triangulum Australe.  The comet will have peaked in brightness by now, but should still put on a reasonable (if rather faint) display for those with large binoculars or telescopes from a dark location.

 For those readers in the northern hemisphere, we have the delights of Comet 21P/Giacobini-Zinner to look forward to.  This comet should be brightening up in the northern celestial hemisphere and should be readily observable - certainly in telescopes and larger binoculars. This regularly returning (6.5 year orbital cycle) comet will be heading northward during July through Cygnus and should be fairly easy to find.  

 

21P/Giacobini-Zinner's path through Cygnus, Cepheus and Cassiopeia during July 2018.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 On 1st July, 21P is to be found around 9 1/4 degrees to the N of Deneb, Alpha Cygni.  The comet continues its path through northern Cygnus, crossing the border over into Cepheus on the 10th/11th July.  On the 27th, Giacobini-Zinner passes over the border into Cassiopeia briefly and then the next day becomes a resident of Cepheus again, such are the jagged borders between the two constellations.  On the 30th, the comet passes into Cassiopeia again, where it will remain, easily found above the constellation’s distinct “W” feature until the latter half of August. The comet will brighten rapidly in August and September, as this apparition passes very close to Earth (0.39 au), so should be a lower magnitude naked eye object then.

 

 Meteors

 

The Delta Aquariids are a fairly decent shower, which peak at around 20 meteors an hour on, or around, 28/29th July.  Fed by their parent comet, 96P/Machholz, this shower is pretty reliable and is the more southern of the two Delta Aquariid showers (the northern equivalent is much less active and peaks in mid August).

 This year, the shower’s peak occurs right at the point of Full Moon in neighbouring Capricornus and while the Total Lunar Eclipse on the night of the 27/28th will give more of a chance of seeing meteors, the radiant will not be particularly high the sky while this occurs and many observer’s attention will be elsewhere during this event!

 

 Deep Sky Highlights In Serpens and Ophiuchus - "Globular Central"

 

 Last month we looked at the galaxy-rich areas of Coma Berenices and the Bowl of Virgo.  This month we drift further eastwards to the interlinked and expansive constellations of Serpens and Ophiuchus.

 

 Serpens and Ophiuchus.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

This area of sky is just adjacent to the plane of the Milky Way and in particular the bulge of our galaxy's central region, around which orbit many of its attendant globular clusters.  Subsequently, if you're a fan of Globulars, this area of sky is an excellent hunting ground.

 We start our journey through "Globular Central" with one of the finest examples in the sky - M5 in Serpens.  This is the most northerly and western of the globulars covered this month.  Discovered in 1702 by husband and wife observing team Gottfried and Maria Kirch, M5 was later rediscovered by Messier in 1764.  This globular is particularly bright at +5.6 mag - and as such can be seen by the naked eye under favourable conditions.  At 3.5 arc minutes across, it is about the same angular size as the famous M13 in Hercules.  M5 as a globular really comes into its own in binoculars and telescopes and is pretty easy to find in either.  Finding it is pretty straightforward: find Beta Librae, or Zubeneschamali and sweep northwards for 10 degrees.  The cluster itself is unmissable - a small telescope will resolve its brighter stars, but a medium to large scope will show and absolute riot of detail - long star chains in its extended halo.  As far as size of globular clusters go, M5 is not quite as large as Omega Centauri, but is still a huge example.  Containing up to half a million stars, the overall tidal range of M5 extends over 200 light years, though the cluster itself is 164 light years across.  M5 lies at about 24-25000 light years distance from us.

M5, HST image.  Image credit: NASA/ESA, Public Domain. 

 

There is quite a large leap to the next Globular, M12, in Ophiuchus.  Over 22 degrees to the East from M5, lies this +6.69 mag object.  At around the same angular size as M5, M12 is considerably closer at 16000 light years distance, but much smaller at 75 light years diameter.  Messier discovered M12 in 1764, had William Herschel made more detailed observations of it in 1783, resolving it into stars and noting its true nature as a stellar, rather than a nebulous object.

 

M12, HST image.  Image credit: NASA/ESA, Public Domain. 

 

Next door to M12, figuratively-speaking, is its "twin" M10.  M10 is slightly brighter at +6.59 and larger at 3.9 arc minutes diameter.  Messier discovered it, again in 1764 and Herschel, again in 1783, recognised it as a stellar object.  M10 is slightly closer than M12 at 14000 light years away and is 82-85 light years in diameter.  In powerful binoculars or a telescope, M10 appears very slightly irregular in shape in comparison to many Globulars - indeed, Lord Rosse commenting on M10's structure in the 19th century remarked that its "most important stars take [on] a spiral arrangement" - most probably commenting on the chains of stars around the globular's core.  William Herschel described M10 as "A very beautiful cluster of extremely compressed stars".  In both binoculars and telescopes, M10 is indeed a lovely object.

 

 M10.  Image Credit: Hunter Wilson, Creative Commons.

 

10 degrees to the East of M10 lies the slightly more difficult M14.  Again discovered by Messier in 1783, M14 is of +7.59 mag and much smaller than the previously-mentioned clusters at 2.6 arc minutes in diameter.  M14 appears slightly squashed in binoculars and telescopes - it is undoubtedly a more irregular object than M10.  A larger telescope is needed to resolve the stars in M14 that the other clusters we've covered thus far - 8-inches and above aperture will be needed to really see this object well.

 

  M14.  Image Credit: Hunter Wilson, Creative Commons.

 

Taking a brief respite from Globulars, 11 degrees to the South of M14, in the direction of Eta Ophiuchi, or Sabik, lies the Box Nebula, or NGC 6309.  The Box is a Planetary Nebula, its brightness is +11.5 mag and it has dimensions of 0.3 x 0.2 arc minutes.  The Box is really the domain of larger telescopes, though 4-inch refractors or 6-inch reflectors will show it.  As with most Planetaries, the Box's size is its strength - although it's small as an object, its brightness is well-condensed as a result. As ever, a decent OIII and UHC filter will help observation, as will the use of high magnification to make increase contrast with the background sky.  The Box Nebular looks a little more keyhole-shaped in long duration images.

 

  NGC 6309, HST image.  Image credit: NASA/ESA, Public Domain. 

 

Returning to Globulars, 5 degrees south of NGC 6309, we can find the  next of Ophiuchius' treasure trove of these objects: M9.  Discovered by Messier in 1764, M9 is a compact target, being 1.9 arc minutes in diameter.  It is also on the fainter side of the mean of objects discussed this month, being +7.71 mag brightness.  M9 is to be found lying 25000 light years away, against a dark lane of the Milky Way and is actually partially obscured by interstellar dust.  If this were not the case, M9 would be similar in brightness to M10 and M12.  It is not easy to resolve stars in M9 - even 10-inch instruments struggle with this task.  A telescope in the 14-16-inch range will be needed to make meaningful observations of M9, though it is fair to say there are other more interesting and beautiful objects in this region!

 

 M9, looking substantially more impressive than it looks through amateur instruments - HST image.  Image credit: NASA/ESA, Public Domain. 

 

The penultimate on our observing list for this month is M19.  This Globular is, like the previously mentioned M14, an irregular, oblate cluster - though much more so.  M19 holds the distinction of being the most irregular of all Globular Clusters and as such appears oval in shape in telescopes.  At +6.76 mag and 2.6 arc minutes in diameter, M19 is pretty easy to spot - though its core, similarly to M9, is difficult to resolve into individual stars.  Part of this difficulty is down to M19's distance, as it lies a remote 29000 light years from us here on Earth, though it is quite a healthy size, being over 140 light years in diameter.  Yet again, Messier was the discoverer of this cluster in 1764.  As M19 sits just 13 degrees high from a latitude of 51 degrees North, atmospherics and local surroundings can be a difficulty in resolving this cluster at its best.  Southern Hemispherical readers will see this interesting object much better!

 

 M19. Image Credit: Hunter Wilson, Creative Commons.

 

If you find M19 is a challenge for observation, the most Southerly of Ophiuchius' Globulars is even more so.  M62 lies on the southern border with neighbouring Scorpius and is never well-seen from Northern European latitudes, though is an interesting challenge to observe.  Discovered in 1771 by Messier, M62 lies 22000 light years away and has a visual brightness of +6.44 mag.  At 1.8 arc minutes it is a compact object and appears somewhat bright as a result.  Again, M62 is slightly irregular as a spheroid and it has been suggested that this is as a result of its proximity to the strong tidal forces of our galaxy's core.  M62 appears well-condensed in instruments of all sizes, with its outer halo being easily seen with larger telescopes.

 

M62. Image Credit: Hunter Wilson, Creative Commons. 

  

Text: Kerin Smith