Name __________________________________ Date _____________ Period _______________
2012-2013 ESGT
Making and using a simple astrolabe
The astrolabe is a device that was used by early astronomers to pinpoint the locations of objects in
space. The instrument itself has had various forms and has been in use for more than 2000 years.
The astrolabe was invented in Greece either by Hipparchus, a 2nd century B.C. astronomer, or
Apollonius of Perga, a 3rd century B.C. mathematician. For many centuries, it was used by both
astronomers and navigators, and especially by the 15th century explorers who used it to determine
latitude, longitude, and time of day.
In this activity, you will use an astrolabe to determine the angle and height of object in different
positions around your school grounds. (MHR Chapter 11 pg.397) You will then determine the
latitude of your location using your astrolabe and Polaris, the north star.
(Developed from: http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_07.html and MHR
Chapter 11)
Vocabulary/Definitions
Word
Definition
Angle of altitude Angle formed between the intersection of a horizontal line and a
line from the observation point of the target object
Astrolabe
Historical astronomical instrument which measures the angle of
altitude
Materials:
• astrolabe drawing
• cardboard/manila folder
• string
• paper clip
• drinking straw
• pen
• paper
What to do:
Part 1: Build your astrolabe
1. Print out the astrolabe drawing
2. Glue the astrolabe drawing to a piece of cardboard or manila folder
3. Cut the astrolabe out with scissors
4. With a hole punch or scissors, carefully make a small notch at each of the lines marked along
the curved edge of the astrolabe. These notches will come in handy when you're measuring
the angle between two celestial objects and you have to hold the astrolabe horizontally.
5. Tape the drinking straw to the edge of the astrolabe marked "Attach straw to this edge." Be
careful to not tape the straw on the astrolabe, but just on the edge.
6. Carefully poke a small hole through the astrolabe where the "X" is marked, pass the string
through it, and either knot the string at the back of the cardboard or tape it there.
7. Tie the small weight to the opposite (front) end of the string .
8.
Part 2: finding the location of objects using the astrolabe angle
Name __________________________________ Date _____________ Period _______________
2012-2013 ESGT
Making and using a simple astrolabe
1. Once you have constructed your astrolabe, use it to find the angle of altitude of the objects
around the classroom.
Angle of altitude = 90° - angle read on the astrolabe/protractor
Object
Triangle on chalk board
Top of wall clock
Fire alarm
Angle of Protractor
Angle of Altitude
Compare the angle of altitude you measured for each object with someone sitting on the other side
of the room.
Were your angles of altitude the same or different? Describe.
Was there a trend? If yes, describe.
Why do you think you got the similarities or differences that you did?
Do you think the stars we see in the night sky in Maryland look the same if you are looking from
somewhere far away like California or Australia?
Part 3: What is your latitude? Using the astrolabe and Polaris
1. Find polaris (North Star)
http://www.instructables.com/id/How-to-find-Polaris-the-North-Star/
2. Use the astrolabe to find the angle of altitude for the North Star
3. Repeat step 2 at least 3 times at least 5 minutes apart.
Time
Angle of Altitude
4. Average your angle of altitude __________________________
5. This number should be close to the known latitude for Maryland. Use your textbook or the
internet to identify the latitude for Maryland. ____________________