Lots to look out for in September with more interesting constellations, the Milky Way, and various planets.  Vernon from the Callander and West Perthshire U3A Astronomy group shares what to look out for this month. 

It is always helpful to have a star chart to follow when navigating and observing the heavens.  A free star chart which also contains lots of additional observational notes is published monthly by Skymaps. Simply go to skymaps.com and scroll down to ‘Download the latest issue’. From here you will can download the northern hemisphere version and save it.  This is then best printed double sided to an A4 sheet. It is worth noting that planets do not appear on skymaps. In this note of astronomical events I have only included items that can be seen either with the naked eye or with a pair of binoculars.

Looking South

The Summer Triangle, Altair, Deneb and Vega, is now high in the South West, with the Great Square of Pegasus high in the southeast. Below Pegasus try looking for the two zodiacal constellations of Capricornus and Aquarius. In Aquarius, just to the east of Sadalmelik (alpha Aquarii) there is a small asterism consisting of four stars, resembling a tiny letter ‘y’, known as the Water Jar. In classical illustrations water is shown flowing from the Water Jar towards the bright Formalhaut (alpha Piscis Austrini).

Another zodiacal constellation, Pisces, is clearly visible to the east of Aquarius. Although faint, there is a distinctive asterism of stars, known as ‘The Circlet’ , south of the Great Square of Pegasus. Still further down towards the horizon is the constellation of Cetus, with the famous variable star Mira at its centre. When Mira is at its maximum it is clearly visible to the naked eye.

Looking North

Ursa Major is now low in the north and to the northwest and Arcturus and much of Bootes sinks below the horizon later in the night and later in the month. In the northeast Auriga is beginning to climb higher in the sky. Later in the month, Taurus, with orange Alderbaran and even Gemini with Castor and Pollux, become visible in the east and northeast. Due east, Andromeda is now clearly visible, with the small constellations of Triangulum and Aries directly below it. Practically the whole of the Milky Way is visible, arching across the sky, both in the north and the south. The clouds of stars become easier to see in Cassiopeia and onwards to Cygnus.

Meteors

After the Perseids shower in August there is little activity in September. One minor period of activity peaks on the 28th and 31st known as the Alpha Aurigids. Which has a low rate of 10 meteors per hour. The southern Taurid shower also begins this month with a low rate of meteors, but it often produces very bright fireballs.

Planets

Mercury is now too close to the Sun to be seen and Venus is the prominent early morning object. Saturn and Jupiter, the brightest of the two, are visible during the evening hours and joined by the Moon on the evenings of 24th and 25th at 20.00hrs to make a fine sight. Mars makes a later night appearance on the 5th and 6th with the Moon at 23.00hrs

Nights of interest

Some of the objects described below are expressed in degrees from the Moon. This is far less complicated to measure than you might think. To measure 10 degrees, hold your hand up towards the sky at arm’s length and turn your hand up so that it obscures part of your view. The width of your hand is 10 degrees and holding just one finger is two degrees.

2nd Sept – Full Moon. Moon is close to its apogee, the point where it is farthest from Earth.
6th Sept –  Moon at its apogee, farthest from Earth
9th Sept –  24.00hrs Moon is close (above) to bright star Aldebaran and below Pleiades (Seven sisters).
9th Sept – Epsilon Perseid meteor shower reaches its peak with maximum of 5 meteors per hour.
10th Sept – 24.00hrs Moon close (to left) of Aldebaran and below Pleiades.
11th Sept – Neptune at opposition when 180 degrees from the Sun, shines brightly and closest to Earth. Visible all night, try looking to the far left of Aquarius from 19.15hrs.
13th Sept -05.00hrs Crescent Moon forms a curve with Castor and Pollux, the Gemini twins over Venus.
15 & 16th Sept –  06.00hrs Crescent Moon passes stars Regulus, the heart star of constellation Leo, and Algieba, a Double Giant, one being bright orange and the other greenish yellow.
18th Sept – Moon at perigee, nearest point to Earth, 359,100km.
22nd Sept – 14.30hrs BST Northern Autumnal Equinox occurs when the Sun crosses the celestial equator.
24 & 25th Sept –  20.00hrs Moon with Saturn, Jupiter and star Nunki, the second brightest in Sagittarius.
25th Sept –  At 22.00hrs the crater Clavius will be in darkness apart from two craters that lie within. This interesting effect is known as the Eyes of Clavius.