How to use a Star Chart

Star charts are a wonderful way to familiarise yourself with the night sky and are a particularly useful tool for complete beginners. Complete star charts which list stars, constellations, star clusters and nebulae can be confusing if you are just starting out but a simplified chart or planisphere can be used by everyone including young children. The term star chart will be used throughout to imply use of the simplified chart or planisphere.

Monthly charts are available in astronomy magazines and on the Internet and can be mounted onto cardboard to make them more robust. Alternatively, perpetual star charts, normally called planispheres, can be obtained which can be used on every night of the year and at any time of the night.

– A tip for beginners –

Studying your star chart indoors and then hoping to memorize it is unlikely to yield successful results and can be frustrating. However, using a torch or other light outdoors will ruin your night-vision. The best way to overcome these difficulties is to purchase a head torch with red LEDs. Not only with this enable you to have both hands free but will help you maintain night vision.

– Using a star chart –

All star charts are presented as a circle and cover all of the night sky from all horizons. Bear in mind that unless you are somewhere that is completely open and flat then not all that is recorded on the star chart will be visible to you but may be behind buildings, trees or hills and mountains.

East, west, north and south horizons will be clearly marked around the edge of the circle representing the night sky. Point yourself towards south and hold the star chart in front of you with the marked south horizon pointing downwards towards the ground. Then raise the star chart above your head. All stars on the chart should now correspond with the night sky. Stars directly in front of you will correspond to the bottom of your star chart as you hold it. Stars directly behind you will correspond to what is shown at the top of the chart.

The stars marked towards the centre of the star chart will be more or less overhead. The stars marked nearer to the circle’s edges will be nearer to the horizon.

You can start with any of the north, south, east or west horizons as long as the way you are facing corresponds with how you are holding the star chart. That is – if facing south then hold the star chart with south pointing downwards, if facing west then hold the star chart with west pointing downwards

– Finding a starting point –

The hardest part of all will be finding a starting point. Once you have found and identified even one star then the rest will follow far more easily. If you are familiar with any star or constellation in the night sky then start there. Otherwise try and pick out one star marked as a bright one on your chart and attempt to trace out the patterns around it. You will notice that not all stars marked on your chart are the same size. The larger the star is depicted, the brighter it will appear to you in the sky. Be aware that the smaller dots are often not visible as stars at all with the naked eye in urban areas with high light pollution.

– Monthly star charts –

If you are using a star chart relevant for one month there will be a time and date recorded on it. Normally adjustments will be written for using the chart earlier or later in the month or at a different time of night. Because of the rotation of the earth, different stars will be visible at different times during the night. Eventually you will learn how to make your own adjustments as you become more adept with using your chart.

– Finding planets –

You will notice a line, sometimes dotted, marked on your star chart called the ecliptic. This line traces the path of the sun which is of course not visible at night. Any planets currently visible in the night sky will always be somewhere near the position of this line as will all 12 constellations of the zodiac. Monthly star charts will often list any planets currently visible.

Eventually, you will become familiar enough with the night sky to notice yourself when something has suddenly appeared where there are no stars.

– Deep sky objects –

Many monthly charts will also list any deep sky objects of interest that need binoculars or a telescope to be seen. Sometimes even the most basic pair of binoculars will give you wonderful views of things that are not visible to the naked eye. For example, train your binoculars on Orion’s belt for an amazing view of the Orion Nebula, a birthplace of stars.

Be patient with yourself. It takes time to begin to map your way around the night sky and it will probably happen very slowly at first. However, once you are familiar with the first few constellations or patterns then many more will follow.