Finding Constellations
Learning to identify various constellations is relatively easy. Finding them in the night sky requires considerably more practice. The following information, taken from Donald H. Menzel and Jay M. Pasachoff, A Field Guide to Stars and Planets, Houghton Mifflin, Boston, MA, 1990, may be of help. Before you begin your "sky watch", it will be helpful to determine which way north, south, east, and west are. Alternatively, if you can locate the Big Dipper, which is often one of the easiest constellations (or "asterism", meaning that it is a part of a larger constellation) to find, you will be able to find the North star and gain a sense of compass direction from that. The Big Dipper is in the northern sky. It may look something like your momís gravy ladle. In the evening sky during autumn, the Big Dipper appears to be right side up, while in the spring-time evening sky, the dipper appears upside down. It is formed by seven stars - three form the dipper handle and four comprise the bowl of the dipper. The bowl of the Big Dipper looks somewhat like a square (actually a trapezoid) and is about 10 degrees across. You can measure this 10 degrees by making a fist and holding your fist up at armsí length against the sky. Your fist should appear to just fit inside the bowl of the Big Dipper. The Big Dipper is fairly easy to find because all of the stars comprising it are quite bright, except for the one which connects the handle to the bowl. Now that you have located the Big Dipper, you can use it to find the North Star, Polaris, as well as other constellations. To find Polaris, locate the outer edge of the bowl of the Big Dipper (the side of the dipper furthest from the handle). The two stars on this outer edge are called the "Pointer Stars." Starting from the Pointer Star at the bottom of the dipper and pretending to draw a straight line from it through the Pointer Star at the top of the bowl, continue drawing a line from the dipper bowl about five times as long as the distance between the two pointer stars, allowing your line to follow the curve of the sky slightly. At the end of your line, you will find Polaris, which is the brightest star in that region of the sky. If you are facing Polaris, you are facing north. Since Polaris remains at this location all year round, once you find Polaris, you know that East is on your right, South is behind you, and West is on your left. Polaris is the last star in the handle of the constellation, or asterism, called the Little Dipper. The Little Dipper is more difficult to find than the Big Dipper because its stars are not as bright. Therefore, you may need a very dark, clear night to find the complete Little Dipper in the sky. The Little Dipper is smaller than the Big Dipper and its bowl hangs down from the handle. After you have stopped to visit the Little Dipper, continue your trip from Polaris to another constellation called Cepheus. Following the same arc in the sky that you drew from the Pointer Stars to Polaris, continue drawing your line about half the distance that you have already come. Imagine yourself to be under the Pointer Stars looking at and past Polaris. Ahead and a little to the right you will find five stars forming a trapezoid that covers about the same area as the Big Dipper. This is Cepheus. The constellation Cygnus, part of which forms the Northern Cross, is beyond Cepheus. Facing Polaris, pass through the right-hand pair of stars forming the trapezoid of Cepheus for about the same distance as Cepheus was from Polaris, reaching Deneb, the brightest star which is at the top of the Northern Cross. Thus, the Big Dipper, Polaris, and Cygnus form an angle of about 120 degrees. Again keying on Cepheus, continue your trip to another constellation called Cassiopeia. Following the same arc in the sky that you imagined from the Pointer Stars to Polaris, continue drawing your line about the same distance that you have already come. Imagine yourself to be under the Pointer Stars looking at and past Polaris. A little to the left you will find a "W" in the sky. This is Cassiopeia, which is comprised of five stars. Note that Cepheus and Cassiopeia are on opposite sides of the same arc, but Cassiopeia is about twice as far from Polaris. Now letís go back to our pointer stars in the Big Dipper, imagine that we are under the Pointer Stars, face along our imaginary line to Polaris, and take a slightly sharper than 90-degree left turn. Follow that line about four times as far as youíve already come to the most prominent group of stars in the sky - three bright stars in a straight line which form the belt of Orion, the Hunter. The other stars surrounding the belt comprise about twice the area of the Big Dipper. In mid-northern latitudes, Orion is clearly visible during the winter, but it is below the horizon and not visible during the summer. Gemini is in the same portion of the sky as Orion. Go back to the Pointer Stars in the Big Dipper, imagine that we are under the Pointer Stars, face along our imaginary line to Polaris, and take a much sharper 70-degree left turn. Follow that line about two and one-half times as far as youíve already come to a trapezoidal group of stars in the sky comprising Gemini. You can also find Gemini by imagining you are under the center star of the handle of the Big Dipper, looking through the star in the Big Dipper where the handle connects and the Pointer Star in the base of the pan, and going about twice the distance between the Big Dipper and Polaris. Gemini covers about one and one-half the area of the Big Dipper. To find the constellation Lyra, we again find the Pointer Stars, face along our imaginary line to Polaris, but this time we will take a less than 90-degree right turn. Travel about twice as far as from the Big Dipper to Polaris and you will find Vega, which is the brightest star in the constellation Lyra. Now letís follow our pointer stars in the opposite direction. Locate Polaris and draw a line from Polaris through the pointer stars. Continue drawing that line in an arc about as far as youíve already come. This time you will come to the constellation of Leo, the Lion. The bright star in Leo is Regulus. Thus, Leo is behind you if you imagined yourself under the Pointer Stars of the Big Dipper looking toward Polaris. Because all of the stars and constellations in
our night sky appear to revolve around Polaris, there will be seasons when
some of the constellations will be so low on the horizon that they will
be difficult or even impossible to see, depending on where you live.
However, there will be other times of the year when the same constellations
will be high in the sky and very visible on a dark, clear night.
To help you know when to find these constellations, you may want to purchase
a good guide to the stars. There are many excellent guides available.
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