Night Sky Notes – July 2018

Night Sky notes for July 2018              Geoff Mitchell

The summer solstice (June 21st) has now passed; the Earth reaches Aphelion (furthest point of its orbit around the Sun on July 6th at a distance of 152 million km (95 million miles) and the evening twilight noticeably fades earlier throughout the month. In July there are two highlights to observe, the Total Lunar Eclipse on Friday 27tth July and the Red Planet, Mars at opposition on the same date.  Shortly after sunset on 27th July the Moon rises in Totality, seen low on the eastern horizon the dim red coloured Moon will be quite difficult to see until twilight fades.  Totality ends at 22: 13 BST, when the first signs of the Moon passing from within the Earth’s umbra shadow appears as brightening on the left (eastern) limb. Over the next hour the partial phase of the eclipse occurs, the pale yellow appearance due to Moon passing through the Earth’s outer Penumbra shadow. The normal appearance of the Full Moon is restored by 00:28 on 28th July. On the evening of Friday July 27th a local public open observing evening is planned for the Total Lunar Eclipse , Luton Astronomical Society  supporting the Bradgers Hill s wildlife group event  (refer to the home page for more information) .

Mars shines brightly at -2.8m magnitude and is unmistakably red in colour appears below and to the right of the eclipsed Moon on July 27th. Telescopes show a small disk (24.3 arc seconds apparent diameter) with some of the dark surface features and the prominent white Martian south polar cap visible . Located in the constellation of Capricornus, Mars is positioned low down for UK observers and favours observers in the southern hemisphere. the 2018 apparition is a perihelic opposition , that is that Mars which has a slightly elliptical orbit is at its closest point to the Sun . This means that Mars and Earth are closest during the current opposition on July 31st at a distance of 57.6 million km, the closet opposition since 2003, which was the minimum possible.

The bright planet Venus can be seen low in western twilight with the planet Mercury visible around mid month however  poorly placed low in twilight . Mercury appears close to a 4.5% waxing crescent Moon,   look half an hour after sunset on July 14th, moonset is 22:20 BST.

The July night sky shows the summer constellations prominently in the south east from late evening and the late spring constellations disappear into the western twilight. The bright planet Jupiter is now low in the evening twilight, Jupiter set less than two hours after the Sun by month end. Currently the NASA Juno spacecraft is orbiting Jupiter, with a further 3 year mission extension planned. Jupiter is thought to be  the first planet in our Solar system to be formed as the latest data from Juno suggest in new theories about how the early solar system formed.

Saturn is found low in the southern aspect in the constellation of Sagittarius. This favours more southern observers as all the planets are low in UK skies. Saturn’s ring system is now wide open, a classic view of this gem of the solar system. Small telescopes will show the rings and the brightest moon Titan. Larger telescopes show up to six or so fainter moons and any white oval features on the planets disk.

The summer night sky contains many fine objects to view for the enthusiast in the late evening hours but also has a few notable events of special interest.  Look to the NW from around 90 minutes to 120 minutes after sunset or similarly to the NE hours before sunrise, when the Sun just below the horizon during the summer months. In the right conditions extremely high clouds at 80 km altitude known as Noctilucent Cloud (NLC) may be seen, NLC’s show a bluish colour and also show filamentary structure.

Our own Milky Way galaxy stretches from the constellation of Auriga [The Charioteer], marked by the bright star Capella and through the constellations of Perseus and Cassiopeia all now positioned low in the north.

In the south east the summer constellation of Cygnus [The Swan] now seen as evening twilight fades. The Milky Way can be seen as a faint band of stars stretching low in the east down through constellations of Aquila [The Eagle], Scutum [The Shield] and towards Sagittarius [The Archer] and Scorpius [The Scorpion] in late evening skies, use binoculars to see the myriad of stars in these rich star clouds, best seen on clear dark moonless evenings from darker locations outside the town.  Sagittarius is best seen in July, the constellation is known for the `Teapot` asterism of stars has rich star fields and some fine star clusters  located above the spout of the Teapot  asterism; however you do need a good southern horizon and finder chart ( see notes ) to spot some of these. Dwarf planet Pluto is located just above `the handle of the teapot asterism`.

Hercules is noted for the Globular cluster M13 containing some 750,000 stars, a nice view in a small telescope The bright star Vega in the constellation of Lyra [The Lyre] is seen low above the north east horizon and Altair in the constellation of Aquila low in the east. Vega, Altair and Deneb, in the constellation of Cygnus form the `Summer Triangle` asterism, a useful sign post for the summer skies.

Look low in the southern aspect late evening to find the distinctive `T` shaped asterism of stars of the `head` of Scorpius . Although rather low as seen from the UK, look below the `T` head of Scorpius to see the `blood red` coloured star Antares.  Antares name means `The rival of Mars`, a red super giant star, with a mass of some 20 solar masses. It has a diameter that, on the scale of our solar system, would be greater than the orbit of Mars. High in the south the bright orange star Arcturus in the constellation of Bootes [The Herdsman] is the brightest star in the northern hemisphere of the sky.

Comet 21P [Giacobini-Zinner ]  is currently placed in Cygnus although a difficult 10.5m magnitude object to spot it continues to brighten as it heads towards perihelion (its closest point to the Sun in September 2018 . The Comet should be a binocular object in our darker autumn skies as it heads southward through Auriga.

Planets in July 2018

Mercury is visible low in the evening twilight (after sunset) in mid July, setting an hour after sunset. Greatest elongation occurs on July 7th.  On the evening of July 14th a thin 4.5% waxing crescent Moon is found just above Mercury (Visible half an hour after sunset ) very low in the western aspect.

Venus is positioned low in the west, visible in evening  twilight , phase decreasing from 0.7 to 0.56

Mars is now positioned in the late evening skies, with opposition on July 27th.  ,shining brightly at -2.8m

Jupiter heads into the evening twilight and is past opposition, cloud belt and Galilean moons visible using a small telescope.

Saturn now just past opposition, low in the south in Sagittarius – a good time to see this ringed `gem`.

Uranus is placed in our– best views in autumn skies.

Neptune is placed in our midnight skies – best views in autumn skies.

Dwarf planet Pluto reaches opposition on July 7th in the Teaspoon asterism in Sagittarius, visible as a faint 14.2m magnitude star.

Moons phases in July 2018

New Moon         July 13th                 Moonless, best time for deep sky observing.

First Quarter     July 20th               Best days to see shadow details in lunar craters (early evening)

Full Moon            July 27th              Best days to see bright ray craters like Copernicus / Tycho.

Last Quarter      July 6th                   Moon visible in daytime skies.  Do not look directly at the Sun.

Meteor shower s                             Southern δ Aquarids, maxima around 28th July, poor, moonlight interferes.

Capricornids, several maxima in July, bright yellow / blue meteors, low rates.


The highlights of the month.

Total Lunar Eclipse, moon rising at sunset in totality as a dim red coloured Moon. Totality ends 22:13 BST

The Red Planet – Mars is now rising by late evening ,very low in the south east , very bright – unmistakable. The planet reaches opposition in late July and is closest to Earth on July 31st – Telescopes show a small disk with some dark surface features and prominent white south polar cap – Refer to web site for details of observing  evening.

Saturn is low in southern aspect; rings almost wide open at 26° DE [tilt] showing Saturn’s North Pole.

Scutum, Sagittarius and Scorpius are visible low in the south as twilight fades. Good star fields seen on moonless evenings. Also note the deep red colour of star Antares ` the rival of Mars ` in Scorpius and globular cluster M4.

Noctilucent cloud – watch the NW skies from 90 to 120 minutes after sunset to see these electric blue clouds.

More detailed sky notes and LAS Newsletters, Finder charts are available to LAS members via the Members` page on the LAS Website www.lutonastrolink.org.uk

Waxing  crescent Moon visibility    . Caution.  Do NOT look at the Sun directly with or without optical aid.  A very thin, 4.5% waxing crescent Moon is visible after sunset from around 21:30 BST to moonset 22:20 BST on July 14thwith Mercury is positioned to the lower left .  .  Only look for the crescent Moon after the sun has completely set.

On July 15th the crescent Moon is positioned close to Venus, note the dimly lit part visible by Earthshine is readily seen with binoculars or small telescope.  Only look for the crescent Moon after the sun has completely set.


 

Sky looking south at 11pm British Summer Time (BST), mid July 2018

In the south the ringed planet Saturn currently is located in Sagittarius, just above the Teapot asterism

Low In the south the constellation of Sagittarius (noted by the famous Teapot asterism) rises late evening. This area of sky is rich in star fields of the Milky Way and has many fine clusters but is only observable in our evening skies during the summer months. Looking  at Virgo we look outside our own Milky Way galaxy towards the external galaxies of the Virgo Cluster , look  to Sagittarius  to into the spiral arm of our own galaxy, the centre of our own galaxy is however too far south to see from the UK

To the west of Sagittarius is the constellation of Scorpius. From the UK we only see the head; the rest of the constellation is visible from more southerly locations. Catch a glimpse in July of the red star Antares (The rival of Mars) on the stem of the `T` asterism low in the south/ southwest.

Three planets, Jupiter, Saturn and Mars are visible low in our southern aspect in July. Mars unmistakably red in colour out shines Jupiter as it reaches opposition late in the month.

The orange star Arcturus is found by following the curve of stars in the handle of the Plough down. The constellation of Bootes, resembles a `kite` or `Club ` in shape.   The star Izar is a beautiful orange/ blue double star visible in small telescopes. To the east of Bootes find the `horseshoe` shaped constellation of Corona Borealis (Northern Crown) and the `Keystone` Asterism in the constellation of Hercules. Hercules also has M13 the famous Globular Cluster, visible to the unaided eye as a misty patch; telescopes show the true wonder of this cluster with over 750,000 stars. Likewise another nice globular is M92 in Hercules.

 

 

Sky looking east at 11pm BST mid July  2018

In July, the summer constellations of Lyra and Cygnus are rising by mid evening, the Milky Way may be visible on moonless evenings from a dark site.  Stretching from low in the south east to low in the north west, this misty band is best seen with binoculars, follow the star fields from Altair, down through Scutum and into Sagittarius is stunning in a dark sky. If you are on holiday and visiting a dark sky site, remember to take a pair of binoculars with you.

Comet 21P Giacobini –Zinner remains faint (10.5m) as a telescopic / astrophotographic object in the rich star fields of the Milky Way.

Total Lunar Eclipse

An open public observing evening for the Total Lunar Eclipse is on July 27th, in support of the Bradgers Hill wildlife group.  Please refer to the LAS web site home page for details.  In addition to viewing the red Moon rising in totality, LAS telescopes will be in use to view Jupiter, Saturn and later evening Mars.

Moonrise 8.52 pm  (mid totality )

Totality ends   10.13pm

Lunar Eclipse ends 11.19pm

Simulated view  looking  east at moonrise on July 27th 2018 (Stellarium)

 

 

 

 

 

Sky looking north at 11 pm BST mid July 2018

The Plough stands with its handle pointing upward follow the pointer’s Dubhe and Merek to find the polestar Polaris. The `W` shaped constellation of Cassiopeia is near to its lowest point in the north late evening.  The Milky Way follows the galactic equator and stretches from east through the constellations of Cygnus, Cassiopeia, Perseus and down into the northern horizon.  The bright star Capella is positioned almost due north and is circumpolar i.e. does not set from our latitude.

 

Sky looking west at 11 pm BST mid July 2017

Mercury very low in twilight   (Only look after Sunset) and on July 15th, Jupiter shines brightly low in the south western aspect.

Open public observing evening for the Total Lunar Eclipse on July 27th, in support of the Bradgers Hill wildlife group – see LAS web site home page for details.  In addition to viewing the Moon rising in totality , LAS telescopes will be in use to view Jupiter , Saturn and later evening Mars .

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More detailed finder charts and newsletters are available to LAS members on the member’s page.

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