The night sky in July 2016

posted 24 Jun 2016, 05:06 by Pete Collins   [ updated 24 Jun 2016, 05:32 ]
by Anne Holt

Sunset 1st:  2141    31st:   2106

New Moon:   4th      Full Moon  19th


Highlights

By the last couple of days in July we start having some proper darkness.  Not much yet but it's a step in the right direction.

The Earth reaches aphelion at 17-24 on July 4th, when it will be 152 million kilometres (94.4million miles) from the sun.

Also on 4th, NASA's Juno mission is due to go into orbit around Jupiter, after a journey of almost 5 years.  . It will study the planet's atmosphere, weather and magnetic field for the next 18 months.

There's still a chance of seeing noctilucent clouds - very high, wispy blue clouds in the North West a couple of hours after sunset or the North East before sunrise.

Constellations

The Summer Triangle (made up of Vega in Lyra, Deneb in Cygnus and Altair in Aquila) is now quite high in the southern half of the sky. Cygnus, with its Northern Cross asterism, and Lyra are particularly prominent.

At the start of the month Pegasus, followed by Andromeda, is rising in the early hours.

As always during the summer months, it isn't the best time to see the zodiac constellations or planets as the ecliptic never gets very high in the sky.  However, if you do happen to visit a dark sky site over the next few months you should be rewarded with good views of the Milky Way high overhead running through Cygnus and down to Sagittarius just above the southern horizon.

Planets

Not a brilliant time for planetary observers this month, all 5 naked eye planets should be visible at times but Mars and Jupiter are now past their brilliant best and Venus has yet to reach it.

Mercury
Reaches superior conjunction on 7th.  Not easily visible this month as, even when it does appear futher from the sun in late July, the angle of the ecliptic at this time means it is still very low in the sky after sunset. On 16th it is half a degree North of the much brighter Venus.  Try looking. just after sunset, from somewhere with a flat, unobstructed Western horizon.

Venus
Still too close to the Sun to be easily seen in the twilight, even at mag -3.9.   Best time to try is near the end of the month, about 30 minutes after sunset.

Mars
In Libra,  mag -1.4. Best seen in early July, when it sets just before 2am.  By month end it will set around midnight and will have faded to mag -0.8, as it moves away from us.

Jupiter
In Leo,  mag -1.9. Stilll shining brightly, low in the western sky before sunset.  Sets about 30 minutes after midnight in early July, around 10.30 by month end.  Durng the month it will fade stlightly to mag -1.7.  On 9th at 2200 it will be 6 degrees West of the 30% lit moon.

Saturn
In Ophiuchus, mag 0.3. Retrograding (moving westwards) slowly through the constellation, which is not considered part of the Zodiac, even though the ecliptic passes through it. Maybe someone thought it would be unlucky to have 13 Zodiac signs. The planet is very low throughout the month,  setting soon after 3am on 1st and a few minutes after 1am on 31st.  At 2300 on 15th, it is 3.75 degrees South East of the 83% lit moon.

Uranus
In Pisces,  mag 5.8. Still at the limit of naked eye visibility - if you have good eyesight and a very dark sky.  Rising just after 1am at the start of July and around 11pm at the end.   In the early hours of 25th it is 5 degrees North of the 61% moon, low in the East.

Neptune
In Aquarius, mag 7.9.  Rising around midnight on 1st and at 10pm at the end of July, when it will reach its highest point in the sky while it is still reasonably dark.

Dwarf planet Pluto, in Sagittarius,  is at opposition on 7th. It is too small to be visible in amateur scopes but might be worth trying to catch photographically,  At opposition it will be 15 arcminutes South West of mag 2.9 Pi Sagittari in the faint teaspoon asterism, which lies slightly NE of the better known teapot.


Meteors

Not the best time for meteor showers, though sporadic activity can be reasonably good in July.

The 2 main showers have radiants which are quite low in our sky and are better seen from further South.

Delta Aquarids:
Active July 21st to August 23rd,  peak 28/29th ZHR 15
Faint, medium paced meteors which don't usually leave trails.  The source of these is not known for sure, possibley comet 96P Macholz.

Alpha Capricornids
Active 13th July to 26th August.  These don't have such a defined peak as other showers but are best seen around 27th & 28th.  ZHR 5, slow moving meteors, could be some fireballs. These are debris from comet 169P/NCAT

Both these showers are sometimes included with the Summer Antihelion Source, which is fairly active during July, as they have radiants on the ecliptic, close to the point opposite the sun.  However they are now generally regarded as being definite showers.

The Perseids are active from 13th July, so some could be seen in the latter half of the month, even though the peak isn't till August.
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