Popular Astronomy

Share to Facebook Share to Twitter Stumble It More...

What's Up for August 2017

It's August and holiday time.  With luck you'll be able to get away to place with a darker sky than you're used to, or at least stay up a bit to make the most of whatever you've got. 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. 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:

Sky for August 17

Wrong way round?

Now don't write in and tell 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 mid August at about 10.30 pm, at the start of the month at 11.30 pm, or by the end of the month at 9.30 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 being summer, 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 right overhead to find a really bright white star, Vega. It's the only bright star close to being 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 a bit lower down towards the eastern horizon than Vega. 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, which if you want to get your bearings is over in the northwest. We've picked it out on the map. If you think of the Plough as a saucepan, then follow its handle round towards the horizon, you come to a bright star called Arcturus, which is about the same brightness as Vega but low down in the western sky. It's also slightly yellowish, and if you thought all stars were white, compare it with Vega to see the difference.

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, clean your glasses.

Map for August 17 with constellation names

All maps 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. 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. Use this to find some other interesting objects, and the constellation of Vulpecula, by clicking here.

This is the time of year to look way down on the southern horizon for the constellation Sagittarius, which form a sort of teapot shape, But unless you have a good, clear night and are well away from city lights, you might not see the stars at all well.

There are plenty of nebulae and clusters visible with binoculars in this part of the sky, so check out our guide to them.

To the left of Vega is Hercules, whose most obvious feature is a parallelogram of stars called the Keystone, though it isn't particularly bright.

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.

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

The month's planets 

The only planet on our map this month is Saturn, but in fact if you look earlier in the evening, at about 9.30 pm, when there is still some light in the western sky, you will see Jupiter as well. They are both quite low in the south, with Jupiter even lower down than Saturn at the start of the month. Jupiter is also the brighter of the two.

So you want to see Saturn's famous rings, eh? Well, the good news is that even a small telescope will show them – you don't need anything expensive. By 'small' we mean something that will magnify maybe 40 or 50 times. Actually, even a larger telescope won't show very much more this year because Saturn is quite low in the sky and our atmosphere makes a real mess of the image, causing it to shimmer and shake like it's made of jelly. But even so, you can still see the rings, and you might be lucky enough to get a steady night, so it's worth a try.

 Mercury and Mars are too close to the Sun to be seen, while Venus is in the morning sky and is a brilliant object over in the east about 4 am.

Where’s the Moon, then?

It begins the month just after first quarter – that’s a half Moon – which was on 30 July, and then full Moon this month is on the 7th. Last quarter is on the 15th, then comes New Moon on the 21st. You might see the crescent Moon in the western twilight on the 24th about an hour after sunset, just to the right of Jupiter, then there's first quarter on the 29th.

We have a whole section of the website devoted to the Moon and its features.

Partial eclipse at sunset
A partial eclipse at sunset can be dramatic. But on 21 August from the UK, the eclipsed part will be at the bottom of the Sun’s disc, and a much smaller area of the Sun will be covered. Photo: Robin Scagell

Solar eclipse

There's a partial eclipse of the Sun in 21 August. In the States this will be a total solar eclipse, and many people are going over there to see it. But from the UK we have to put up with a small partial eclipse, and to make matters worse it will occur at sunset, so it won't be easy to observe. But if it's clear over to the west you could get a great view of the eclipse close to the horizon.

It's always difficult to be sure how to observe the Sun when it's low down. Although normally you should never look at the Sun, when it's low down we often look at the sunset and don't worry about it because the Sun's glare is dimmed by the atmospheric haze. But we are usually looking not at the Sun itself but the surroundings. Staring directly at the Sun can be just as dangerous as when it is high up, and looking through binoculars can be even worse because the Sun's light is spread over a larger area of your eye. 

At the same time, the traditional safe ways of viewing the Sun, such as by projecting its image through a pinhole or using a mirror, might not work because the Sun is dimmer than when it is high up. Take a look at our help file on using a mirror and be ready to use this if the Sun is bright. Also take a look at this PDF leaflet which tells you all the ways in which you can observe the Sun safely during an eclipse, and tells you much more about solar eclipses.

The eclipse takes place just around sunset, which occurs around 8 pm, and how much you see of the eclipse and the exact time of sunset depends on where you live in the UK. So get out there about 7.40 pm and watch to see the Moon take a tiny bite out of the bottom edge of the Moon and then move slowly across the bottom edge. From the Home Counties the Sun sets before the eclipse is over, but those farther north or west could see the whole event, which only lasts an hour or so. 

Perseid meteors
Two Perseid meteors.
Pic: Robin Scagell

August’s shooting stars

August is usually a great month for shooting stars – what astronomers call meteors. You can expect one every ten minutes or so on most nights, as long as you have a fairly dark sky. Around Saturday 12 August we get the annual Perseid meteors, which are one of the year's strongest showers, and they should be worth staying up late for – if the clouds keep away, of course. But by late, we do mean late. It doesn't get really dark enough to see them until about 10.30 pm, and then the rates start to increase until about 3.30 am! Oh well, it is holiday time, and maybe you can stay up a bit later than usual. But don't be fooled by it being August. It can still get pretty cold in the UK in August, so grab a blanket or two to keep yourself warm. 

The Moon will be in the sky after about 11 pm, so that will be a bit of a problem, but if you face in the opposite direction from the Moon you stand a better chance of seeing the meteors.

The Perseids don't just appear in Perseus (which is shown on our map at the top) but can appear anywhere in the sky. They appear to come from the direction of Perseus in the northeast. You may hear that there could be 80 an hour visible, but don't take that too seriously. That's a theoretical number based on perfect conditions, which won't apply. You might see one every few minutes, though there are sometimes bursts of activity with a few in a single minute.

You can find out a lot more about what to do when you see one in our guide to observing meteors. And there's a 35-minute video from our Meteor Section Director (recorded in 2013) telling you all you need to know about observing the Perseid meteors.

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