What’s Up for September 2023

sheila_nightskyIt’s September and term has started again.  But look on the bright side – or rather the dark side. It gets dark at a reasonable hour in the evening and at least you won’t get frostbite. But how do you make sense of all those stars?

That’s where we come in. Use our easy-to-follow sky guide and you’ll be out there stargazing in no time. OK, you may have an app on your phone that tells you what the names are, but it really helps to start finding your way around and remembering those names. You will need a star map, and you will need to know how it works. This may seem obvious, but there is a knack to understanding these things. Here’s our map for this month:

Sep 23 CDC 22h

Wrong way round?

Now don’t send us a stroppy message telling us that we have the points of the compass all wrong. This is a map of the sky, so you have to hold it over your head. When you do this, east and west will be the right way round.

It shows the whole sky, so the scale is quite small. Normally you turn to see different parts of it, so to see the view looking north, for example, hold the map upside down with north at the bottom.

The map shows the sky in the middle of the month from the UK at about 10 pm, at the start of the month at 11 pm, or by the end of the month at 9 pm. All times are BST.

TIP If you aren’t sure of the direction of north from your location, click here for a page on Getting Your Bearings.

Making sense of the stars

This still being summer, almost, the best way to find your way around the sky is to use the Summer Triangle. Actually this is not as obvious as it seems, because this triangle still remains visible well into the autumn and even the winter, but the fact is that it’s a key feature of the summer skies so we might as well stick with the name.

Find it by looking fairly high up to find a really bright white star, Vega. It’s the only bright star anything like overhead, so ignore all other stars and look really high up. The next star of the triangle, Altair, is halfway between Vega and the horizon. Altair has a fainter star on either side of it – look at the map to get the idea. The other star is Deneb, which is now more or less overhead. If you can’t spot these three stars straight away, remember that the map above is on quite a small scale, so think big and you should spot it.

Many people recognise The Plough (or Big Dipper), which if you want to get your bearings is low down in the northwest. We’ve picked it out on the map. If you know how to use the Plough to find the Pole Star, keep going and you’ll find the W-shape of Cassiopeia, one of the most easily recognised constellations in the sky.

Now use the map below to find more patterns nearby, but don’t expect to see those convenient lines helping you to see the patterns. If you do see them, you’ve been watching too much TV and ought to get out more.

Map produced using Stellarium software.

Other constellations to look for

Once you have found the Summer Triangle, you can now start to look for some constellations. There’s Cygnus, the Swan, also known as the Northern Cross. It is a large cross-shape with Deneb at the top, marking the tail of the swan which flies down the Milky Way with outstretched wings. “What Milky Way?” you ask. Fair point. You live in Neasden or Newcastle and can’t see this Milky Way which is shown on the map. You’ll just have to take our word for it that it’s there.

To find out more about Cygnus, including why it is unsuitable for children, click here.  One of the best-known stars in Cygnus is Albireo, a fairly faint star marking the head of the Swan, or the foot of the Cross. Midway between Altair and Albireo is a rather cute constellation called Sagitta, which means Arrow, along with two neighbours, Vulpecula and Delphinus. They may be small, but they have a lot going for them, so take a look.

Going back to the Summer Triangle, find Altair and follow the line of the three stars down towards the south until you came to a brightish star as shown on the map, Alpha Capricorni. You should be able to pick out that this consists of two stars – a double star.  Actually, the fainter star is about six times the distance of the brighter one.

The map shows the Milky Way as a pale band crossing the sky. This is a good time of year to look for it, though you won’t see it from light-polluted areas. The best chance of seeing it is high up in Cygnus, but if you go on holiday to a dark-sky area it can appear so bright you will wonder why you can’t see it at home. The map shows the Great Rift, a dark zone down the middle of the Milky Way caused by dust clouds.

If you want a map with all the constellation names on it, click here.

Where are the planets?

Jupiter and Saturn are both in the evening sky at the moment. Jupiter is the brighter of the two, over to the east. If you have binoculars take a look and you will see that it is accompanied by up to four tiny companions, which are actually its brightest moons, known as the Galilean moons. Guess who discovered them…. Each night you look, they will be in different positions as they orbit the planet. If you have a telescope, you’ll see the planet’s globe, and probably its cloud belts crossing it.

Jupiter and Saturn
Jupiter and Saturn on 31 July 2020, photographed with an 80 mm refractor. Credit Robin Scagell

Saturn is fainter, and is fairly low down in the south. You might think it’s a star but if you look carefully you’ll see that it isn’t twinking like a star.  Planets don’t usually twinkle! You might also notice that it is slightly yellow compared with Jupiter. It’s also well worth a look through a telescope, as it has those amazing rings. Although it’s low in the sky you’ll still be able to see the rings, even with a small telescope, so take a look at it if you can before it gets too low later in the year.

Venus is in the morning sky, rising over in the east before sunrise and very bright at the moment. Mercury joins it during the second half of the month, but fainter and lower down.

Mars is  too close to the Sun to be seen this month.

For a detailed list of things happening in the sky, click here. And bear in mind that members of the SPA get more info about what planets are in the sky and how to observe them. Find out more here and join the society here!

What about the Moon, then?

At the very start of the month the Moon is almost full, with the actual full Moon being on 31 August. Last quarter is on the 6th, followed by new Moon on the 15th. After this you might be able to spot the crescent Moon low down in the north-western twilight about half an hour after sunset on the 18th, but you will need a very clear sky and probably a phone app to show you where to look. First quarter is on the 22nd, then full Moon is on the 29th.  Sorry, no eclipses this month.

Everyone’s heard of the Harvest Moon, and this year it will be the full Moon on the 29th. The Harvest Moon is the full Moon closest to the autumnal equinox, which is the day when the Sun is overhead at the earth’s Equator, moving southwards, and day and night are equal around the world. This falls on 23 September this year, so the closest full Moon will be that of 29 September.

The Harvest Moon got its name because it rises as the sun sets around harvest time, helping farmers to get the harvest in by the light of the Moon. Actually the harvest is usually all in by September, and farmers now have much brighter lights on their machinery anyway, so even they can sit back and enjoy it rather than being out in the fields toiling away by its light.

Harvest Moon
Harvest Moon. Photo: Robin Scagell

We also have a whole section of this site about the Moon and what to observe, so do take a look.

Get more helpful info

OK, you’ve read all this for nothing, now comes the plug. This page is brought to you by the Society for Popular Astronomy, which is a really great society to join. It’s based in the UK but there are members in other countries as well. It doesn’t cost much to join, and there is a special rate for Young Stargazers. At least take a look at what we have to offer.

Text by Robin Scagell