Night sky highlights - September 2017

This month, have a look for Venus, Regulus, the Moon, Mars and Mercury appearing to line up. (Details given are for London and may vary for other parts of the UK).

Top three things to see this month

12th Sep – Catch Mercury at greatest western elongation before sunrise in the east.

18th Sep – Look for Venus, the star Regulus, the very thin crescent Moon, Mars and Mercury all appearing to line up in the eastern predawn sky.

25th – 26th Sep – Spot the Moon, the red star Antares and Saturn in the south-west after sunset.

2 September

Image of star map for 2 September 2017

Look towards the east to spot Mars beside Mercury and Regulus – the brightest star of the constellation Leo. They will be quite faint so be sure to have a look before the Sun rises.

6 September

The Moon reaches full Moon on the morning of the 6th. Parts of the Moon which are struck by the Sun’s light can reach 120 degrees Celsius and the far side of the Moon which isn’t lit up by the Sun can dip to -150 degrees Celsius.

Photograph of Solstice Full Moon Over Sounion © Anthony Ayiomamitis, Astronomy Photographer of the Year Earth and Space Commended 2010
Solstice Full Moon Over Sounion by Anthony Ayiomamitis

10 September

Jupiter will be 3.1 degrees North of Spica. Look to the western sky as the sun sets and if you have a good pair of binoculars or preferably a telescope you may be able to see the 4 Galileans Moons Io, Europa, Ganymede and Calisto beside Jupiter.

12 September

Image of star map for 12 September 2017

  • Mercury will be at greatest Western elongation. This means that from our perspective Mercury is as far west from the Sun as it can be and it will now start to move eastwards and appear to get closer to the Sun. It’s the best time to look for this rather faint planet – look towards the east before sunrise.
  • On this evening, the Moon will be beside Aldebaran in its waning gibbous phase. Aldebaran is an old red giant star that’s 40 times wider than our Sun – placed at the centre of our Solar System its surface would extend half way to Mercury!
  • Look higher up in the Eastern sky and you may also be able to make out an open cluster of stars called the Pleiades – on a clear night you should be able to spot 7 points of light so they’re often called the Seven Sisters too!

15 September

After the major Perseid meteor shower in August, there’s comparatively less meteor activity this month. The primary peak of the Alpha Aurigids falls on this night and although it is a minor meteor shower with a low hourly meteor rate (roughly 10), they are bright and relatively easy to photograph. Head out after midnight and view with just your eyes. The meteors can be seen all over the sky but will appear to radiate from the constellation of Auriga in the east.

18 September

Image of star map for 18 September 2017

There will be a five-member spectacle to view in the pre-dawn sky. You’ll have to be up before sunrise to see Venus, Regulus, the very thin waning crescent Moon, Mars and Mercury appearing to line up diagonally in the east.

22 September

We reach the autumnal equinox on the evening of the 22nd. This is when the Sun crosses the celestial equator and night and day is of approximately equal length. Going forward, we will have less hours of daylight compared to darkness.

25 September

Image of star map for 25 September 2017

Look in the south western sky for the Moon beside the red star Antares in the early evening and on the following night the waxing crescent Moon will have moved to nestle beside Saturn.

Look Up! podcast

As well as taking you through what to see in the night sky each month, Radmila and Dhara pick their favourite astro news story. For September, they're chatting about the asteroid Apophis and how likely this Near-Earth object is to collide with the Earth and the launch of the first supercomputer to the International Space Station by SpaceX - dubbed the Spaceborne Computer.

Stargazing tips

  • When looking at faint objects such as stars, nebulae, the Milky Way and other galaxies it is important to allow your eyes to adapt to the dark – so that you achieve night vision.
  • Allow 15 minutes for your eyes to become sensitive in the dark and remember not to look at your mobile phone or any other bright device when stargazing.
  • If you are using a star app on your phone switch on the red night vision mode.
  • Need a stargazing telescope or decent binoculars? Check out our range of high-quality observing equipment recommended by Royal Observatory astronomers:

See our range of observing equipment

Share your astronomy pictures

Don’t forget to share your pictures of the night sky with us on Twitter @ROGAstronomers or via Facebook

Insight Astronomy Photographer of the Year

Image of Auroral Crown by Yulia Zhulikova
Auroral Crown by Yulia Zhulikova

Come and see this year’s amazing entries and winner to the world’s biggest astrophotography competition in our free exhibition at the Royal Observatory. The 2017 exhibition will open on Saturday 16th September. 

See the Insight Astronomy Photographer of the Year competition

See more of the night sky

Come on an amazing tour of this month’s night sky in our Sky Tonight live planetarium show

See the Sky Tonight planetarium show

Central image: Venus Rising © Ivan Slade