Now that September is here, the nights are getting noticeably longer again. On 1st September, sunset is 20:13 and by 22:25 it is completely dark. The weather in September is usually still mild enough so that you can go out and observe comfortably, although the nights can get chilly so it’s time to start taking out the heavy clothes again. Wrapping up and keeping warm can be the difference between enjoying a nights astronomy and coming inside early.
This September there are a number of conjunctions that you will be able to see with just the naked eye.
- 5th September – Moon and Mars in the south before sunrise.
- 6th September – Moon and Mars extremely close in the south before sunrise.
- 11th – 15th September – Venus is very close to the Beehive cluster before sunrise, also joined by the Moon on 14th.
- 24th & 25th September – Jupiter, Saturn and the Moon in the south around 8pm.
Sun and Moon
|Date||Sunrise (Irish Time)||Sunset (Irish Time)|
Not visible this month.
September is a great month to spot Venus. The only catch is that you will have to stay up very late or get up very early. It rises about 3 hours before sunrise and will be extremely bright in the East. It will be unmistakable.
Mars is getting better all the time and will dominate the sky through September. During the month of September, Mars will reach a stationary point. This is where the planet appears to stop moving against the background stars. It will then start to move west, this is as a result of the orbital movements of Earth and Mars. It will appear as a salmon – pink coloured star and will have already risen when the sky gets dark. It will start off in the east and move towards the west as the night goes on.
Jupiter remains well placed in September. It is already risen when darkness falls. At the start of the month it sets around 1.15am and by the end of the month it sets at 23:15. It will be a bright star in the south.
Saturn is visible close to Jupiter, it also will have risen before darkness falls. At the start of the month it sets around 2am and by the end of the month it sets at midnight. It will be a bright star in the south.
Stars and Constellations
The above sky chart is for 23:00 on 15/09/2020. You can click on the chart to open a new tab and bring you to Heavens Above. On this website you can generate a custom chart for the time and date you wish. The spring constellations of Leo (the lion) and Virgo (the virgin) are gone with Bootes (the herdsman) now setting in the west soon after sunset.
High overhead are Cygnus (the swan), Lyra (the liar) and Aquila (the eagle). The brightest stars in these constellations are Deneb, Vega and Altair and they make up the Summer Triangle which hangs on high in the sky during September. The misty path of the Milky Way also runs through this area of sky.
In the south at this time of year, is the constellation of Scorpius (the scorpion). This is the direction of the centre of our galaxy, the Milky Way. It never rises very high in the sky from Ireland, but if you look in the direction you should be able to make out that it is almost misty or milky with stars.
The autumn constellations are gaining height in the east early the night and as the night goes on they will rise higher and higher. The great square of Pegasus (winged horse) is visible along side Andromeda (mythical princess). If you live in a very dark location you may be able to see the Andromeda Galaxy with your naked eye. If you have binoculars you will easily pick it out. from the square of Pegasus follow the curve of Andromeda until you get to the T shaped turn. Go to the right here for a short distance to find it. It is the most distant object visible without binoculars or a telescope.