This month the nights become longer and we move towards unsettled weather. The autumn constellations are starting to show. Ursa Major, or the Plough, can be found low in the North. The ‘W’ of Cassiopeia is not far from the overhead point
Also on view this month we have, Aquarius the water carrier, Cetus the sea monster, Capricorns the sea goat, Pices the fishes, Piscis Austrinus the southern fish and Delphinus the Dolphin.
The summer triangle of Altair, Deneb and Vega remains high up. The southern sky is dominated by the Square of Pegasus. The bright star Capella in the constellation of Auriga the Charioteer is becoming more noticeable in the east. It will be overhead in winter evenings.
Although the four stars that form the Square of Pegasus are not the brightest, once found they will be easily recognised again. It is always an interesting project to count how many stars you can see within the square; you might be surprised by the result.
If you use the two right hand stars of the square and draw a line to the south you will reach a bright star very low in the sky. This star is Fomalhaut, in the constellation of Piscis Austrinus.
This month on Thursday, 22nd September we have the autumn equinox. After this date the nights noticeably lengthen.
Scour the eastern horizon just before dawn to spot Mercury. It will be putting on its best performance of the year, as it brightens from magnitude +0.5 to –0.5. Mercury will be at its greatest elongation on 28th September.
Located in the western sky, Venus is gradually moving upwards in the dusk twilight. Shining at magnitude –3.8. The brilliant evening star sets at 8pm.
You will find Mars low in the evening sky to the south west in the constellation of Ophiuchus. It sets around 10pm. Shining at magnitude –0.1. Mars lies to the left of a fainter Saturn.
In the evening sky look for Saturn, low down in the south-west. located to the right of the brighter Mars in the constellation of Ophiuchus. Shinning at magnitude + 0.6 , it sets around 10pm. The star forming a triangle with Saturn and Mars is the red giant Antares in the constellation of Scorpius.
The most distant of the gas giants, Neptune is at opposition on 2nd September and is at its closest to Earth. You will still need a telescope to spot this distant object. Shinning with a measly magnitude of +7.8 Neptune lies above the horizon all month long in the constellation of Aquarius. On the 15th of the month Neptune hides behind the Moon
New Moon on September 1st
First Quarter September 9thh
Full Moon September 16th
Last Quarter September 23rd