Using the Big Dipper to Find North

March 30, 2012


Finding north using the stars

For centuries, sailors navigated throughout the world using only the stars to guide them. Armed with only a sextant, they found their way through the Mediterranean Sea and even across the Atlantic Ocean with great accuracy.

Although the sextant has long sense been replaced with more modern technologies such as Global Positioning Systems (GPSs), we can still look to the stars for direction in a pinch.

The Big Dipper

In ancient times, men looked to the evening skies regularly. They observed that some stars appeared to form the basic outline of something recognizable: a lion, a fish, a swan. One of the most easily recognizable outlines is the Big Dipper.

As it’s name implies, it looks looks like, well, a large dipper used to scoop water from a barrel. Technically, the Big Dipper isn’t a constellation. It’s a asterism, an easily identifiable part of a larger constellation. In this case Ursa Major, also known as the Big Bear.

Like all heavenly bodies, the stars that make up the Big Dipper appear to rotate across the night sky. At different times of the year and evening, the Big Dipper will be at different locations. Sometimes it’s visible; at other times it’s below the horizon relative to us.

Finding Direction

Identifying the Big Dipper, if it’s visible, allows to you to easily find Polaris, the North Star. Simply trace a line between the last to stars of the “cup” of the Big Dipper. Follow that line approximately 4 and 1/2 times the distance between the two stars and there you’ll find the North Star.

The North Star is sometimes called the Pole Star because it is located in line with the axis on which the Earth rotates. This means that no matter the time of night, the Pole Star can be found directly above the North Pole. It’s the only star in the sky that doesn’t appear to move as the night passes.

Using the Big Dipper to find north

One really nice thing about the Big Dipper is that it is found almost directly opposite Cassiopeia, another constellation that may be used to locate Polaris. Due the rotation of the Earth, one if not both of these tell-tale constellations may be seen above the horizon, unless of course it’s a cloudy night.

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8 Comments on “Using the Big Dipper to Find North”

  1. poormansprepper Says:

    Silly question for you,

    I know that there is the big and the littel dipper, how do you know that you are looking at the right one….say on an evening were there is spotty clouds cover and you might not see both together…

    I hope that this question makes sense



    • Joe Says:

      What a great question, PoormansPrepper!

      The following web site shows both the Big Dipper and the Little Dipper. You’ll notice that the Big Dipper has a more pronounced bend in the handle of the dipper whereas the Little Dipper is more curved in its handle.

      To my eye, the Big Dipper is the most easily recognizable of the two.




    • Andrew G. Plourde Says:

      The Big Dipper is larger than the Little Dipper, and its stars are brighter. In fact, often the only stars visible in the Little Dipper are the North Star and the two at the far end of the dipper, Pherkab and Kochab. So don’t get hung up trying to make out each star of the Little Dipper. The only one you’re interested in is Polaris. And the only reason you’re interested in the Big Dipper is so you can use the pointer stars to find Polaris.

      Andrew Gee


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