Sky Notes October 2015

Sky Notes for October 2015                          Geoff Mitchell

The October night sky now sees the autumn constellations prominent early evening and heralds some familiar winter constellations rising by late evening and contains many fine objects to view with both binocular and small telescopes.

The constellations of Cygnus, Lyra and Aquila can be seen slipping westward early evening; 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 east, through the `W` shaped constellation of Cassiopeia high in the north east and along  the cross shaped  constellation of Cygnus. This faint band of stars best seen on dark 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. Over head the particularly rich star fields running through Cygnus show the spiral arm of our galaxy and some of the obscuring dust in the form of the dark banding of the Cygnus Rift – Binoculars show these star fields well.

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. The constellation of Auriga contains some nice star fields and star clusters such as M36, M37 and M38 visible in binoculars and small telescopes.

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.  Another fine globular cluster is M15 in the constellation, best seen telescopically.

In the north west Ursa Major, The Plough or The Great Bear is seen low with its handle or tail parallel to the horizon mid 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.

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. Saturn sets in twilight and is lost into the daytime skies by late October.

In the east mid evening the seven sisters’ (Pleiades, M45) star cluster and constellation Taurus heralds the autumn skies of a new observing season. It is worth noting just what difference the change to GMT (UT) on Sunday 25th October makes on the night skies at the end of the month. The  Hyades star cluster makes the characteristic `V` shaped asterism in the constellation of Taurus and noted for the bright, red foreground star   Aldebaren , `the eye of the bull` , which now rises by early evening.   On October 29th, the almost full moon passes in front of Aldebaren in a lunar occultation, the star disappearing for around a hour. Observe with a telescope and you will see the star suddenly reappear around 22:46 GMT from behind the dark lunar limb.

Jupiter rises in the constellation of Leo (The Lion) in the early hours in late October and will feature more in the winter and spring skies. However Mars, Venus and Jupiter group together for a dawn display looking east  in late October and are joined by Mercury mid month with a thin crescent moon on October 11th (06:00 hrs BST )

Planets in October

Mercury is low in dawn twilight during October greatest elongation Oct 16th and is 2° from a thin crescent moon 06:00 hrs BST on Oct 11th

Venus shines brightly at dawn and reaches greatest elongation (46°), just 1.5° from Jupiter on October 26th

Mars is visible very low in the east pre dawn with a conjunction with Venus late October (1.5° apart Oct 31st)

Jupiter shines in the east in the constellation of Leo (The Lion) pre dawn in October.

Saturn is a evening twilight object in October and has conjunction with the Sun in late November.

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. (see notes)

Moons phases in October

New Moon         Oct 13th                 Moonless, best time for deep sky observing and Comets              .

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

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

Last Quarter      Oct 4th                   Moon visible in daytime skies.  Do not look directly at the Sun.

Note – Clocks change to GMT (i.e. go back 1 hour), Sunday October 25th.

GMT is the same as UT (Universal Time, Greenwich Mean Time beginning at midnight)

Meteor showers

Orionids range October 16th to 30th, maxima 21st to 24th – Fast meteors with persistent trails, quite favourable.

Taurids range October 20th to November 30th – Slow meteors, some bright events, favourable.

Draconids maxima October 9th, parent comet Giacobini- Zinner, period 6.6 years (no activity listed for 2015)

The Highlights of the Month

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

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

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

Double cluster, on the Perseus /Cassiopeia border, nice pair of star clusters, binocular, medium magnification.

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

Asteroid Vesta at opposition October 3rd in the constellation of Cetus (The Whale) – Binocular / Telescopic

Lunar occultation of star Aldebaren in Taurus  , disappears  21:48 GMT , reappears 22:46 GMT , Telescopic.

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