Measuring angular size in the sky and Polaris

 

First, visualize the horizon around you as a giant circle, with you at the center.  Directly above you is the point in the sky known as zenith.

 

There are 360 degrees in a complete circle. 

 

Clench your hand into a fist and hold it in front of you with your arm outstretched.  The width of your fist (from the pinky side to the thumb side) is approximately 10 degrees of angle.  This means if you hold your fist out at arm’s length along the horizon, it will take about 36 fists to make a complete circle around you.  Use this to measure the angular width of large distant objects, like a building or the height of a flagpole.

 

Now, hold your pinky out at arm’s length.  The width of your pinky is about 1 degree of angle.  Use this to measure finer details.  Try measuring the angular width (in degrees) of a bus or a car using your pinky.

 

At night, locate the asterism known as the Big Dipper.  Record the date and time of night.  To the best of your ability, measure the length of the asterism, from the front of the ladle to the end of the handle, in degrees, using your fist and your pinky.

 

Also, measure the angle above the horizon the Big Dipper happens to be at this time, and make a sketch of how the dipper is oriented in the sky with respect to the horizon. 

 

Using the two front stars in the ladle as a guide, locate the star known as Polaris, the North Star.  Your instructor will show you how this is done in class.  Determine the angular separation between the Dipper’s front stars and the North Star.

 

 

 

 

Date and time: ___________________________

 

Angular length of Big Dipper: _______________ degrees

 

Angular height of Big Dipper above horizon: ___________ degrees

 

Angular separation between

Big Dipper’s front stars and the North Star:  ___________ degrees

 

Sketch is on other side of paper…