MAKING A SIMPLE SEXTANT TO FIND LATITUDE          

by Diane Vardner
Will Rogers Intermediate School
Lawndale, CA 90260

THEMES:  Stability , Scale and Structure
GRADE LEVEL:  5- 10
GROUP SIZE:  2 students per group 
SETTING:  Classroom, outside, or auditorium
APPROXIMATE TIME REQUIRED:  1 class period plus 1 homework 
assignment

MAJOR CONCEPTS

1. Most stars change their positions as Earth rotates and 
revolves.
2. The axis of Earth is inclined with respect to the poles and 
remains constant.
3. The North Star can be used to determine geographic north.
4. The numbers specifying location on Earth are known as latitude 
and longitude.
5. The angle at which the North Star can be observed relative to 
the horizon differs in each part of the world. At the equator, the 
angle is O degrees.  At the North Pole, Polaris is observed at 90 
degrees. In the northern hemisphere, latitude is the same as the 
angle which the North Star is observed above the horizon.

SCIENCE PROCESSES
Observing, Interpreting Data, Using Numbers, Measuring

VOCABULARY
1.  Polaris:  The North Star, the best known and brightest star in 
Ursa Minor (the Little Dipper).
2.  Latitude Lines:  Imaginary lines that run parallel to the 
equator, used to find location on Earth relative to north and 
south. 
3.  Horizon:  The line where the sky appears to meet Earth.

MATERIALS NEEDED
Per student: protractor, tape, jumbo paper clip, scissors, 20 cm 
string, metric ruler, clear plastic straw

GENERAL PROCEDURES
See attached worksheet.

GENERAL INFORMATION FOR TEACHERS
1. The determination of latitude is based on the formula (latitude 
of any place in the northern hemisphere) = (latitude of the North 
Star at same place).
2. When working inside, use a large room like the gym or 
auditorium and locate items near the ceiling at the opposite end 
of the room.
3. When working outside, locate tall buildings, poles, trees, etc.
4. This activity goes well with studying explorers in history and 
angles in math.

REFERENCES
Degani, Meir H., Astronomy Made Simple

WORKSHEET

HOW CAN YOU FIND LATITUDE USING THE NORTH STAR?  MAKING A SEXTANT.

Name:
Date:                 Per.:

MATERIALS: Protractor, jumbo paper clip, 20 cm string, clear 
plastic straw, tape, scissors, metric ruler.

PROCEDURE:
1.  Tape the straw to the protractor so that the straw goes 
through the 90 degree and center mark (or center hole).
2. Tie the string to the paper clip. Making sure that the string 
hangs freely, tape it to the center mark. (Note: the string should 
go through the O degree mark if the straw is held parallel to the 
ground.)
3. Pick an object high on the ceiling or outdoors above ground.  
Sight this object through the straw. Press the string against the 
protractor when it stops swinging and read the scale on the 
protractor. (Read the scale that ranges between O to 90 degrees.) 
This is the angle of the object above ground.
4. Take two more readings of this object and average the results. 
(Make sure you are at the same location!)
5. Pick 1 more object and take three readings, averaging your 
findings.
6. Go outside on a clear night. Use a compass to locate north. 
Find the Big Dipper. Use the pointer stars to locate the Little 
Dipper and the North Star.
7. Find the angle of Polaris above the horizon.  Repeat step 4 and 
find the average for Polaris. Find the latitude of your City on a 
map. How do the two numbers compare?

OBJECT #1                    
READINGS
1st     2nd     3rd      AVERAGE (sum / 3)      
OBJECT #2                    
READINGS
1st     2nd     3rd      AVERAGE (sum / 3)      

Polaris

FOLLOW-UP QUESTIONS
1. What are some disadvantages to using a sextant?
2. How could knowing your latitude help you? (Imagine you are an 
explorer.)
3. At the equator, where would you look to find Polaris?
4. At the North Pole, where would you look to find Polaris?
5. What is the latitude of the equator? The North Pole?

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This material was taken in whole, or adapted, from, "THE CATALYST 
COLLECTION: OUTSTANDING EARTH / SPACE SCIENCE ACTIVITIES" Edited 
by Gaylen R.  Carlson,  Ph. D., California State University, 
Fullerton, Department of Geological Sciences,  Fullerton, CA 
92634-9480, (714) 773-3882.
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