Learning the sky might seem tricky at first. There are so many stars, and unlike visiting a new town or city, the stars keep on moving around! But don’t give up! With a few tips and tricks, you’ll soon start to tell your Aries from your Aldebaran.
The first step is to look at a star map for the date and time when you are observing. These days, many people will use an app on their smart phone or tablet that shows them the correct stars just by holding it up to the sky. But if you don’t have one of these, try using the star chart on our Young Stargazers’ Sky Guide, or our Sky This Month map.
The app should know which direction you’re viewing, but with a map you need to work it out for yourself. Try first to work out which is south, which is the direction of the Sun at midday. Hold the app, or map, in front of you facing south and work out which constellation – star pattern – you’re viewing. Once you’ve picked out just one of the constellations on view, you can work your way through the others.
Even though apps might seem to be the perfect answer, it’s a good idea to treat them just as you would a map, and pick out each constellation one by one. That way, you’ll really learn the sky, rather than relying on the app.
Month by month
As the Earth goes around the Sun, we see a slightly different part of the whole sky each night. If you observe at the same time each night, over a month or so you’ll notice that new stars have started to appear in the eastern part of the sky and old friends are starting to set in the west. After a year, you’ll have seen the whole sky visible from your home site and everything is back where it started.
Everything, that is, apart from the planets. These move slowly against the starry background, so they aren’t shown on general star maps but only on those designed for the date in question. They stick close to a track in the sky known as the ecliptic, which is also followed by the Sun and Moon. So from the UK you’ll never see a planet directly overhead, nor in the north. You can often tell a planet from the stars just by looking at it. A planet doesn’t usually twinkle like a star, because it is a globe, rather than a point of light. Twinkling is caused by our turbulent atmosphere bending the light beam, so the beam of light from a star is more likely to be disturbed than that from a disc, even though it’s too small to be seen as such by eye.
After you’ve identified each planet (which may take some time, as they aren’t always visible), you’ll be able to see differences between them. Mercury, the closest planet to the Sun, always remains close to the Sun in the sky, so it’s only ever visible in the twilight after sunset or before sunrise. Venus, next out, does the same, but it moves much farther from the Sun and you can sometimes see it in a dark sky. It’s brilliant white, and it the brightest natural object in the sky after the Sun and Moon.
Mars comes next, but as it and the other planets are farther out from the Sun than Earth, it can be seen far from the Sun, and even in the midnight sky. It has a distinctly reddish colour – after all, it’s known as the Red Planet. Next comes Jupiter, which is white or a slightly creamy colour, and usually very bright. Saturn is slightly yellowish, and being far from the Sun only moves slowly through the sky. It moves only a short distance to the left (east) each succeeding year. It will be visible only in summer for some years to come.
Uranus and Neptune are too faint to be seen without a telescope.
The Moon – friend or foe?
Whether or not you like the Moon depends on your interests as an astronomer. That’s because its brightness tends to overcome the fainter objects, such as nebulae and galaxies, which go by the general name of deep-sky objects. But for planetary observers it’s no real problem at all because the planets are bright enough to shine through moonlight and even light pollution. And there are many people who are fascinated by the Moon itself.
As you know, the Moon goes through phases, caused by the changing illumination of the Sun as the Moon goes around the Earth. The sequence begins with a crescent Moon in the west after sunset, then after a few days we see the half Moon. The illuminated part gets fatter every evening, and the brightening Moon starts to wipe out the fainter objects in the sky. By full Moon it rises just as the Sun is setting, opposite it in the sky. Following this, the Moon rises later and later until for a couple of weeks it’s out of the evening sky altogether, and you can only see it in the early morning sky. These evenings are the best time to do your deep-sky observing.
Learning your way around the Moon works the same way as learning the sky. Use a Moon map to pick out one feature, such as one of the darker “seas” (not seas at all, but actually darker plains), then work from there to the others. The areas around the seas are easiest, because there are fewer craters, but the light areas, known as lunar highlands, are a jumble of craters and it can be hard to tell one from another.
Ideally, you should observe every evening, starting with a crescent Moon, because the changing phase very helpfully reveals a new section each night so you can build on your previous evening’s knowledge. But with the British climate being what it is, you’ll probably have to make the best of odd nights when you can.
We have a special Moonwatch area of this website where you can find out lots more about the Moon and how to observe it.
Finding deep-sky objects
These are such objects as nebulae, star clusters and galaxies – often referred to as “faint fuzzies” because for the most part they are, well, fuzzy and quite faint. On a really good night out in the country you can see a few of these with the naked eye, such as the Andromeda Galaxy, the Lagoon Nebula and a few star clusters, but they are tantalisingly vague. With binoculars a lot more start to become visible, and with a telescope you can see a whole lot more, and make out details in some of them. But – and this might be a big disappointment – you won’t usually see any of the dramatic colours that show up in photos of the same objects. Nor are they as brilliant as the photos show. Even bright objects such as the Orion Nebula look pale and translucent. It’s not that you just need a bigger or better telescope – the problem lies with our eyes. At low light levels, we lose colour sensitivity. Even on a bright moonlit night out in the country you can’t see colours in the landscape — the grass, and everything else, are just shades of grey.
What they look like
Binoculars or a telescope make deep-sky objects easier to see by magnifying them, and the larger the aperture of the instrument, the better they look. But they still appear dim, and you need dark surroundings to be able to see them, even through a large telescopes. So while we don’t want to put you off before you’ve even started, don’t get your expectations too high! The fun comes in finding these remote objects, often thousands or even millions of light years away, with your own eyes.
What if you live in a town? The range of objects that you can see is certainly reduced, but star clusters in particular can shine through the light pollution and the murk because the stars are points of light and are not as badly affected by the bright sky background as the faint fuzzies. Having said that, it’s better to concentrate on the bright objects such as the Moon and planets.
Tricks of the trade
Given reasonably good skies, there’s still a knack to finding deep-sky objects. You need to get to know your telescope or binoculars well. If you have a telescope, read our help file on getting to know how to use it. Even with binoculars, experience helps. To start with it can be hard to know which star you’re looking at because they all seem much brighter through binoculars and it can be hard to know which star you’re looking at. So get to know the field of view of your binoculars by looking at recognisable small star groups. In late autumn, winter and early spring the well-known Pleiades or Seven Sisters star cluster is an ideal starting point as you can see straight away how much magnification you’ve got and how much brighter they seem. In summer, try looking at the bright star Vega, almost overhead, and the fainter stars
Once you’ve got to grips with what stars look like through your instrument, you can start to find those elusive deep-sky objects. While you can find the Pleiades or Vega easily enough, most other objects are not usually visible with the naked eye so they take a bit of finding and you’ll need a fairly detailed star map of some sort. The ones you get on phone apps are good, and we like Stellarium, which can be used on a desktop or a phone.
You need to work from a star you can actually see with the naked eye and which you can find with your binoculars or telescope finder. Then you use what’s called star hopping, which means looking for patterns of fainter stars that will lead you to your target. This isn’t always easy, but your ability will get better with practice.