Night Sky Notes – September 2016

 Night Sky notes for September 2016            Geoff Mitchell

The September night sky is perhaps offers some of the best observing conditions. With the autumn equinox for northern hemisphere observers on September 23rd the mix of summer and autumn contains many fine objects to view with both binocular and small telescopes. Also this month there is a Penumbral Lunar Eclipse **

The constellations of Cygnus, Lyra and Aquila can be seen high overhead and into the south; these are noted for the bright stars of Deneb, Vega and Altair respectively forming the `Summer Triangle ` asterism.

The Milky Way stretches from Perseus rising in the north east, through the  `W`  shaped constellation of Cassiopeia  in the north east , along  the cross shaped  constellation of Cygnus. This faint band of stars best seen on moonless evenings continues down through the obscure constellation of Scutum and on in the direction of the centre of the Milky Way (not visible from the UK) low on the horizon.

In  late September, Mars is now located in Sagittarius, close to the `spout ` of the Teapot Asterism, very low in the south / south west  early evening .  Look at the faint band of light of the Milky Way stretching high overhead and low into the south. Use binoculars to reveal the rich star clouds that show a myriad of stars and some of the dark rifts, regions of the Milky Way spiral arm obscured by dust clouds on clear moonless evenings

Auriga has the bright star Capella and can be seen low in the north east early evening, Capella is circumpolar from UK latitudes and so is always visible.  In the east the constellation of Pegasus, noted for its `Square ` shape and the adjacent constellation of Andromeda noted for The Andromeda Galaxy (M31) , visible to the unaided eye as a faint fuzzy patch on moonless evening  can now be seen mid evening . The Square of Pegasus is a useful sign post constellation and also is a good test for sky conditions, (how many faint stars you see within the square is indicates just how good your seeing conditions are).  Follow the two end stars (Scheat and Markab) down to find the star Fomalhaut in the constellation of Pisces Australis (The Southern Fishes), visible very low on the southern horizon late evening at the end of the month .

In the North West Ursa Major, The Plough or The Great Bear is seen low with its handle or tail parallel to the horizon late evening?  Use the right hand pair of stars  Dubhe  and Merak  (The pointers ) to find the faint pole star Polaris  and hence  the position of North .  Follow the curve of Ursa Major’s tail to the orange star Arcturus in the constellation Bootes (The Herdsman) low in the west. To the east of Bootes find the `horse shoe ` shaped constellation of Corona Borealis (Northern Crown) and the `Keystone asterism ` in the constellation of Hercules also noted for the globular cluster M13 containing around 750,000 stars, a good view with modest telescopes.

Saturn is visible now very low in the south west in twilight and is not well placed, however the rings are wide open, a classic view of this ringed gem.  Uranus in the constellation of Pisces and Neptune in the constellation of Aquarius are now both evening objects that can be located using binoculars and a suitable finder chart. A good starting point is to locate the Square of Pegasus and the ring of stars below the Square known as the `Circlet` in the constellation of Pisces (The Fishes), then star hop using the finder chart. Uranus and Neptune are notable due to the blue and green colour, Telescopes show a tiny disc rather than the sharp pinpoints of stars in the field of view.

In the east mid evening the seven sisters’ (Pleiades, M45) star cluster and constellation Taurus heralds the forthcoming autumn skies of a new observing season.

** September 16th the Harvest moon rises at 19:14 BST in Penumbral Lunar Eclipse, appearing rather pale in colour, mid eclipse is 19:54 BST and the eclipse ends at 21:54 BST when the Moon returns to its normal brightness.

Planets in September 2016

Mercury is at inferior conjunction on September 12th, returning to dawn skies late September.

Venus shines brightly low in evening twilight and will become more prominent later in the autumn

Mars is visible low in the south early evening, located in the constellation of Sagittarius.

Jupiter slips into the evening twilight setting with the Sun by late September –poorly placed.

Saturn visible very low in the south west early evening, rings are wide open in the constellation of Scorpius.

Uranus rises late evening in the constellation of Pisces. (Binocular / Telescope required)  (See notes )

Neptune in Aquarius rises early evening (Binocular / Telescope required). The constellation of Aquarius is positioned low in the south east by mid evening  Neptune is at opposition on September 2nd ( See notes)

Moons phases in September

New Moon         Sept 1st                Moonless, best time for deep sky observing and Comets .

 First Quarter      Sept 9th              Best days to see shadow details in lunar craters (early evening)

** Full Moon       Sept 16th           Best days to see bright ray craters like Copernicus / Tycho.

Last Quarter      Sept 23rd             Moon visible in daytime skies.  Do not look directly at the Sun.

** September Full Moon is the Harvest Moon and is coincident with a Penumbral Lunar Eclipse.

Autumnal Equinox occurs on September 22nd 15:21   BST, Day and night being equal length

Meteor showers

Piscids, range September to October, maxima September 9th and 21st – rather low rates.


The highlights of the month

September skies, Milky Way visible high over head on moonless evenings in darker skies.

**Look at the Moon illusion effect at moonrise around Full Moon September 16th, the Harvest Moon rising in penumbral eclipse [looking unusually faded] as it passes through the Earths penumbra shadow.

Uranus and Neptune, binocular objects to find using suitable finder charts

M31 the Andromeda Galaxy is visible on moonless evenings, best seen in binoculars.

Double cluster, on the Perseus /Cassiopeia border, nice pair of star clusters

Albireo, the star Beta Cygnii is a nice blue/ yellow double star seen telescopically

A 5% waxing crescent moon is positioned close to Venus in twilight on September 3rd

DSLR astrophotography – Sky photography on moonless evening – 28mm /50mm lens – manual focus to infinity.  Set ISO / ASA 1600, exposure 30s, remote cable release, tripod mounted – Have a go at capturing some of the star fields through Cygnus around Deneb (NGC 7000 N.American Nebula) and Scutum


More detailed sky notes and LAS Newsletters, Finder charts are available to LAS members via the Members` page on the LAS Website  Artificial satellite and International Space Station visible passes and bright Iridium flares – check the  home page for posting s of details of favourable observing times.

Waxing  crescent Moon visibility    . Caution.  Do NOT look at the Sun directly with or without optical aid.  A thin 1.4 day old , 2% waxing crescent moon is visible after sunset on September 2nd from around 19:50pm to moonset at 20:15 BST. Planet Venus in twilight and Jupiter lies to the north of the crescent Moon tonight. On September 3rd the 5% crescent Moon lies to the right of Venus, moon set is 20:38 BST

Jup - Ven Sept 16



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. 





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



LAS general finder chart for Uranus for September / October 2016, positions shown at 5 day intervals
Note – Circles show the field of view of typical 10×50 binoculars Uranus at opposition October 15th




LAS general finder chart for Neptune for September / October 2016, positions shown at 5 day intervals
Neptune is visible using 10×50 binocular at magnitude 7.8m at opposition September 2nd
Note – Circles show the field of view of typical 10×50 binoculars