All good sailors need a sextant to mark their location of latitude and
to find the North Star. If you want to make a sextant,
you will need a piece of cardboard, a plastic straw, a paper clip, string
( about 4 inches long ), a small weight ( you can use a washer or a fishing
weight ), scotch tape, protractor, pencil, and scissors. You will need
to start with the piece of cardboard and protractor. Draw lines 1/2 inch
from the edge of the cardboard.
Place the protractor and mark the angles, from 0 to 90 degrees on the cardboard.
See Fig. 1.
Label the degrees in ten units ( 10, 20, 30, 40 ). Make smaller
marks in between the ten marks to represent the units of five. Cut
off the extra part of the paper with the scissors. Punch a hole where the
0 degree and 90 degree lines meet, and thread the string through.
Tie the string to the paper clip to keep the string from slipping back
through the hole. Then, tie the other end of the string to the weight.
After you've done that you tape the straw to the top of the paper.
When you sight the north star through the straw the string will tell you
the degree of latitude of you location. See Fig.2.
The north star is easy to find on a clear night. Just face the northern half of sky and locate the Big Dipper. The Big Dipper is a group of stars that look like the side view of a pan with a handle. The Big Dipper moves in a circle around the North Star. In the winter, the handle of the dipper will be pointing downward. In the spring, the dipper will be upside down. In the summer, the dipper will be pointing up. In the autumn, the dipper will be right side up. All of these different positions are caused by the rotation of the Earth.
On a clear night notice the two clear bright stars in the front of the dipper. These are the two stars farthest from the handle. They point to the North Star, these stars are called the pointer stars. Guess the distance between these two stars. Count five of these stars in a imaginary line from the end of the Big Dipper, and you should see the North Star. The North Star is also the end star in the handle of the Little Dipper.
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