How to use a star chart

Star maps are a bit like the road maps we use to help us travel to new places, but instead of important landmarks like churches, museums, forests or lakes, the stars and constellations are our road signs. Understanding how to use a star chart is one of the easiest ways to start learning the night sky, but it can be a bit daunting knowing what to do with one, so let’s go back to basics and see how they work (you may even pick up some clues for the competition, too!)

First things first: you need to make sure you’re using the correct star chart for the correct month, or at least the right time of year. We keep our online star charts updated for every month, so there’s a good place to start. Another handy tool is a planisphere; these are rather useful since you can turn the disc to set the sky for any time on any night of the year.

Before you try to match your sky map to the night sky you first need to find out which direction you’re facing. Take a look at where the Sun rises in the morning and sets in the evening – this gives you east and west respectively. Another way would be to look at a map of your area, which will have the compass points labelled and should help you find out which way your house is facing. Now you are ready to match your map to the night sky. If you are looking towards the south you need to move your sky chart so that it shows the southern sky, too. Most star charts look like they have the compass points around the wrong way round, but because it is a map of the sky you have to hold it over your head, facing down, and then east and west will be the right way round. Clever, huh?

Most star charts show brighter stars as big dots and dimmer stars as small dots, so look for the brightest stars first to help you get your bearings. For the winter sky, locating and identifying Orion is a good place to start as this constellation not only has three stars in a straight line making up Orion’s belt, but also two bright stars Betelgeuse and Rigel that are easy to spot. Once you’ve found Orion you can move your star chart around to match the positions of the stars in the sky, and use your map to navigate the rest of the sky! In spring, Leo is the one to start with, and in summer use Cygnus, quite high up. In autumn, Pegasus is the one to start with.

Top tip: Don’t try to learn all the constellations at once. Find a constellation (like Orion) that is easy to recognise and then hop to the nearby constellations until you can find them all without a star chart!

Click here to see this month’s star chart and put your knowledge into action!