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.
Venus returns to the evening sky this month for the first time since August 2015. The brilliant planet shines at mag. -3.9 and from mid-July can be seen after sunset low down above the west-northwestern horizon for observers at tropical and southern latitudes. As previously noted, Mercury passes close by Venus on July 16th.
Venus then climbs slightly higher in the sky each subsequent evening and by the third week of July should be visible from locations such as Florida and the Mediterranean. However, those living in northern Europe, Canada, northern Russia and northern Asia will find it more difficult to spot the planet (if at all) due to the bright evening twilight.
Mars is visible as soon it's dark enough as it moves direct (eastwards) among the stars of Libra. Now well past opposition the "Red planet" fades in brightness from magnitude -1.4 to -0.8 and shrinks in apparent diameter from 16.3 to 13.1 arc seconds this month. However, it still remains large enough for telescope observers to make out a reasonable amount of surface detail. By the end of the month, Mars sets about midnight for northern temperate latitudes but a couple of hours later from more southerly locations.
The surrounding region of sky also contains Saturn (mag. +0.2) east of Mars and first magnitude red supergiant star Antares (α Sco - mag. +1.0) to the southeast. Of the three objects Mars is the brightest followed by Saturn then Antares.
A nice evening pairing occurs on July 14th when the waxing gibbous Moon passes 8 degrees north of Mars.
Jupiter is located in Leo. Even though long past opposition and heading towards solar conjunction it remains a lovely evening object this month, visible towards the west just after sunset. However, by months end from northern temperate latitudes the giant planet sets only 1.5 hours after the Sun although observers in the Southern Hemisphere have a couple of extra hours visibility. During July, the brightness of Jupiter decreases slightly from mag. -1.9 to -1.7 with its apparent size shrinking from 34 to 32 arc seconds.
On July 9th, the waxing crescent Moon passes 0.9 degrees south of Jupiter. An occultation is visible from the southern tip of Africa (10:11 UT).
Saturn is only one month passed opposition and can be seen after sunset towards the south from northern temperate latitudes or towards the northeast from southern temperate latitudes. It remains observable for most of the night. Bright red Mars is positioned about 15 degrees west of Saturn with both planets better seen from southern and equatorial locations.
The beautiful "Ringed planet" continues it's retrograde motion through the constellation of Ophiuchus close to the border with Scorpius. As the Earth slowly distances itself from Saturn the apparent brightness and size of the planet continue to decrease. Its magnitude fades from +0.2 to +0.4 with its apparent diameter shrinking from 18.2 to 17.6 arc seconds as the month progresses.
Saturn's wonder of course is its ring system. They are currently wide open and even a small 80mm (3.1-inch) scope will easily show them. Larger telescopes with their increased light gathering and power capabilities display much more detail. For example, a 200mm (8-inch) scope under good seeing conditions at 250 to 300x magnification reveals 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.
On July 16th, the waxing gibbous Moon passes 3 degrees north of Saturn.
Uranus, mag. +5.8, is located among the stars of Pisces. At the beginning of the month from northern temperate locations, the planet rises 4 hours before sunrise improving to midnight by months end. The visibility period from locations further south is slightly better still.
Under dark skies Uranus is faintly visible to the naked eye, although from most populated areas optical aid is required. The planet is currently positioned close to the mid point of an imaginary line connecting omicron Psc (ο Psc - mag. +4.3) and epsilon Psc (ε PSc - mag. +4.3).
On July 26th, the last quarter Moon passes 3 degrees south of Uranus. Four days later the planet reaches its first stationary point signaling the beginning of this year's opposition period. It then commences retrograde motion.
Neptune continues to move retrograde in Aquarius. The distant planet is approaching a September 2nd opposition date and is therefore well placed for observation throughout the month. At the start of July, it rises about midnight from northern temperate latitudes and even earlier still for those located further south. By months end it can be seen in late evening.
Neptune is positioned approx. 30 degrees south of the Great Square of Pegasus and half a degree southeast of lambda Aqr (λ Aqr - mag. +3.7). First magnitude star Fomalhaut (α Psc - mag. +1.2) is located 20 degrees south of the planet. Neptune is the only planet that's never bright enough to be seen with the naked eye but it's relatively easy with binoculars or small scopes. During July, it marginally brightens from mag. +7.9 to +7.8.
On July 23rd the waning gibbous Moon passes a degree north of Neptune with an occultation visible from central and eastern North America at 5:36 UT.
Solar System Data Table July 2016
|Date||Right Ascension||Declination||Apparent Magnitude||Apparent Size||Illum. (%)||Distance from Earth (AU)||Constellation|
|Sun||5th July 2016||06h 57m 17.5s||22d 47m 02.4s||-26.7||31.5'||100||1.017||Gemini|
|Sun||15th July 2016||07h 38m 07.4s||21d 31m 24.6s||-26.7||31.5'||100||1.016||Gemini|
|Sun||25th July 2016||08h 18m 06.6s||19d 39m 15.0s||-26.7||31.5'||100||1.016||Cancer|
|Mercury||5th July 2016||06h 46m 24.4s||24d 08m 45.7s||-2.1||05.1"||99||1.321||Gemini|
|Mercury||15th July 2016||08h 17m 39.9s||21d 32m 56.8s||-1.2||05.1"||94||1.311||Cancer|
|Mercury||25th July 2016||09h 32m 55.7s||16d 00m 39.2s||-0.5||05.5"||81||1.217||Leo|
|Venus||5th July 2016||07h 31m 00.2s||22d 48m 51.0s||-3.9||09.7"||99||1.713||Gemini|
|Venus||15th July 2016||08h 23m 08.8s||20d 40m 34.4s||-3.9||09.9"||98||1.693||Cancer|
|Venus||25th July 2016||09h 13m 28.8s||17d 33m 43.6s||-3.9||10.0"||97||1.668||Cancer|
|Mars||5th July 2016||15h 19m 29.5s||-21d 07m 10.4s||-1.3||15.9"||92||0.590||Libra|
|Mars||15th July 2016||15h 24m 52.4s||-21d 33m 53.3s||-1.1||14.7"||90||0.635||Libra|
|Mars||25th July 2016||15h 35m 10.8s||-22d 13m 08.7s||-0.9||13.7"||88||0.685||Libra|
|Jupiter||5th July 2016||11h 15m 30.9s||06d 04m 15.3s||-1.9||33.9"||99||5.809||Leo|
|Jupiter||15th July 2016||11h 21m 05.1s||05d 27m 23.0s||-1.8||33.2"||99||5.945||Leo|
|Jupiter||25th July 2016||11h 27m 13.9s||04d 46m 49.4s||-1.8||32.5"||100||6.068||Leo|
|Saturn||5th July 2016||16h 37m 35.5s||-20d 19m 44.9s||0.2||18.1"||100||9.160||Ophiuchus|
|Saturn||15th July 2016||16h 35m 26.7s||-20d 17m 13.4s||0.2||17.9"||100||9.261||Ophiuchus|
|Saturn||25th July 2016||16h 33m 50.7s||-20d 15m 55.8s||0.3||17.7"||100||9.383||Ophiuchus|
|Uranus||5th July 2016||01h 29m 53.9s||08d 45m 16.0s||5.8||03.5"||100||20.124||Pisces|
|Uranus||15th July 2016||01h 30m 30.1s||08d 48m 31.8s||5.8||03.5"||100||19.957||Pisces|
|Uranus||25th July 2016||01h 30m 48.3s||08d 50m 01.6s||5.8||03.6"||100||19.789||Pisces|
|Neptune||5th July 2016||22h 53m 45.4s||-07d 58m 04.7s||7.9||02.3"||100||29.412||Aquarius|
|Neptune||15th July 2016||22h 53m 15.8s||-08d 01m 28.1s||7.8||02.3"||100||29.276||Aquarius|
|Neptune||25th July 2016||22h 52m 36.4s||-08d 05m 48.9s||7.8||02.3"||100||29.160||Aquarius|