Astronomy how to use a Star Chart

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Knowing how to implement a star chart effectively is imperative if you wish to familiarize yourself with stars and constellations. With a little practise, one can become familiar with the night sky and notice the changes as they occur. Stars of various hues and brightness are visible to the human eye at night. But without the use of a star chart, it can be extremely difficult to determine which is a star and which is a planet. While planets tend to wander amongst the constellations throughout the year, stars remain in the same place within their constellations. A typical star chart shows the relative positions of stars and their brightness.

To use a star chart effectively, you must first find one which is appropriate for the time of the year you are doing your stargazing. It is imperative that you do this as the earth orbits the sun and the sun’s glare hides a great number of stars. Star charts often come in a set of four, one for each season. These are excellent tools for beginners as well as professional stargazers. Some star charts are extremely detailed therefore you will need to find one which suits your stargazing expertise. More detailed star charts list constellations, star clusters, nebulae, stars and so much more. But beginners can become completely overwhelmed by them so opt for a simplified one to start off with.

Monthly or seasonal star charts can be purchased in bookstores, most newsagents, on the Internet and through a host of astronomy and book clubs. One can pop star charts into sleeves which are specifically designed to keep them in prime condition, mount them on a small backboard, or roll these up and place them in a cylinder type container for storage. One may wish to invest in a ‘perpetual’ star chart .These specific star charts can be used every night of the year. A perpetual star chart (calendar) is good for a span of many years. Many consist of 14 one-year star calendars. Star charts can be a little different to each other, but the basic symbols for deep sky objects are very much the same.

Prior to using even the most basic star chart, you must understand how to pinpoint the positions of the stars in the sky. The earth spins on it’s axis and all stars appear fixed in place in relation to each other and move together within the night sky from east to west. Now imagine the earth as a gigantic celestial sphere with all the stars visible on its inner surface. The Celestial North is marked by the North Star Polaris. Therefore when reading your star chart remember that Celestial North is not up but towards Polaris. Now one will need to ensure that they are not stargazing in a light polluted area. Your observation site should be well away from strong light sources. Choose a night when the sky is bright and clear as possible from smog and so forth. A little moon present will be ideal.

You will now need to ascertain that your star chart is the right way around so you can match the stars in the sky with your star chart. Those using a planisphere star chart will note that it consists of two sections, the top represents the night sky and shows you all the constellations. The bottom section is the section which allows you to adjust your observation according to the season, time, date, location and so forth. Most of these come with an attachment so that you can lock these together. Once you have adjusted the bottom card according to the right time, date etc, you are now ready to read your star chart. Give yourself at least half an hour outdoors to allow your vision to become fully night adapted. This takes between 15-20 minutes on average.

Make sure you carry a red light torch with you as this will allow you to consult your star chart without interfering with your night vision. Check your star chart for location, some star charts will do this automatically. Now choose a direction. The majority of first-time star gazers start by looking south. This is where northern hemisphere observers see the ecliptic. This is where the planets are said to prowl. Match your star chart with the sky so that you can easily find your way across the sky. If you are observing north, position the star chart so that it shows the northern sky. The majority of star charts show North, South, East and West, so position North to the bottom of the chart. Now it will be so much easier to find specific stars in the sky.

Most experienced astronomers advice amateurs to look for star patterns we are all relatively well acquainted with such as; the Milky Way and the Big Dipper. One will notice their star chart will show the brightest stars by their size. The larger the better and the more easily found. You may have noticed (in some astronomy books) that constellations have a type of pattern to them when one joins stars with lines. Many have a certain shape to them such as ‘the saucepan’. If you familiarize yourself with these specific shapes long before you head outdoors for your very first reading of a star chart, you will find it so much easier to recognize things in the sky. Many experienced astronomers call this ‘following the lines’.

Feast your eyes on the brightest stars in the sky and see if they make some type of specific shape. Now look at your star chart to match this. Makes stargazing a whole lot easier doesn’t it? Simply use your imagination and envision a line going from one star to the next. Many star charts will show the equatorial grid which defines right ascension and declination which are the longitudes and latitudes of the sky. These are extremely beneficial for those who are hoping to view a newly discovered comet. Some constellation lines are shown on star charts as stick figures which approximate how the ancients associated the positions of stars with figures of animals, mythological heroes, villains and objects.

Other have constellation boundaries which tell you precisely in what constellation a specific object can be found. Your star chart may even come complete with object labels which are very useful for identifying and locating Messier objects. These are the star clusters and nebulae which most astronomers are eagerly seeking. The Internet has a host of excellent websites where one can print out star charts for free. One can also find many free downloadable star chart software programmes online. Head over to for an idea of what is available on the Internet. Study, research and learn. Practise makes perfect, so have patience. Remember that stargazing is intended to be an enjoyable experience. Perseverance will definitely pay off in the long term.

More about this author: Janette Waldron

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