The Astrolabe Student Target SS.4.A.3.1, SC.4.E.5.1 Materials Copies of the below text and questions Pencil or pen Copies of the astrolabes for students to make with the materials listed on the astrolabe plan Warm-­‐up In the 21st century, we use hi-­‐tech navigation tools to travel on the world’s oceans. Some of these devices include Global Positioning Systems (GPS), which use orbiting satellites to track our position anywhere on earth. During the Age of Discovery methods of navigation were very crude by today’s standards. However, mariner’s navigation tools did develop quickly because of the need of European explorers venturing to the New World discovered by Columbus in 1492. Some of the instruments early navigators used varied and included the quadrant, astrolabe, cross staff, hourglass, compass, map or nautical chart, and other devices. Lesson Read the following passage about the quadrant and astrolabe and then answer the questions. The quadrant was a celestial navigation tool used to find latitude. It was a quarter panel of wood or brass with degrees marked on the outer edge of the arch, a plumb line, and sight along one edge. The instrument was used to measure the altitude of the star Polaris. The reading was taken where the plumb line intersected the degree on the outer edge of the arch. Like the quadrant, the astrolabe was used to find latitude. It was a circle made of brass or wood with degrees on the edges and a moveable alidade or sighting arm. It could be used at night to sight in on Polaris to obtain the latitude. If the alidade had a sight with pinholes on either end, it could be used during the day by measuring the sun. The astrolabe was used by holding from the ring at the top and the sight moved until the sun shined through the pinholes. The degree was then read. If used at night, it was held by the ring with one hand, the other hand moved the alidade until it was sighted in on Polaris, then the degree was read. Sometimes the astrolabe was by a pair of sailors, one to sight and the other to steady the device and take the reading. Historical Society of Palm Beach County Claiming La Florida: On Board with Juan Ponce de León 2012-­‐2013 Questions 1. Sailors used the astrolabe to find what? 2. Is the alidade a non-­‐moving sight or a movable sight? 3. Could sailors use the astrolabe during the day? 4. If sailors used the astrolabe at night, what star did they aim at to find the latitude? Enrichment Make your own astrolabe. Print the attached plan for an astrolabe and have students make their own navigation instrument. Have students follow the instructions and report their finding. Astrolabe from The Museum of Florida History, Tallahassee, Florida Please visit www.museumoffloridahistory.com/education/resources.cfm You can also visit the National Oceanic and Atmospheric Administration and download an astrolabe to make, at http://oceanservice.noaa.gov/education/projects/makeyourownastrolabe.pdf Vocabulary Quadrant Astrolabe Alidade Polaris Historical Society of Palm Beach County Claiming La Florida: On Board with Juan Ponce de León 2012-­‐2013 Answers Questions 1. Sailors used the astrolabe to find what? Latitude 2. Is the alidade a non-­‐moving sight or a movable sight? It is movable 3. Could sailors use the astrolabe during the day? Yes, by using the sun. 4. If sailors used the astrolabe at night, what star did they aim at to find the latitude? They would use the star Polaris. Historical Society of Palm Beach County Claiming La Florida: On Board with Juan Ponce de León 2012-­‐2013 Name
MAKING AN ASTROLABE
During their voyages, Spanish saliors used simple instruments and
knowledge of the sun and stars to guide them. Follow these steps
and you’ll be able to deter mine latitude the same way.
Directions
1. Cut out a cardboard
semicircle with the
measurements shown.
4. Tie the weight to the
other end of the string.
8 inches
7. Sight Polaris through
one end of the straw.
Without moving the
straw, pinch the end of
the string against the
protractor.
4 inches
2. With a protractor as
your guide, turn your
semicircle into a protractor
by writing the number
and degree markings shown.
Don’t write within the top
1/2 inch of the cardboard.
3. Tie one end of your
string around the center
of your straw.
5. Glue your straw just
o
above the 90 marks.
6. On a clear night, take
your astrolabe outside.
Face north (get your
bearings from the western
part of the sky where the
sun sets). Look for the two
stars in the Big Dipper
farthest from the handle.
They point to Polaris, the last
star in the Little Dipper’s
handle.
From The Museum of Florida History, Tallahassee, Florida
8. Return to a lighted area
to read the degrees indicated
on your astrolabe. Use an
atlas to determine the
approximate latitude of your
location. What do you notice
about your astrolabe reading
and your latitude as shown in
the atlas?
Materials: cardboard,
a soda straw, a 12-inch
piece of string, a weight
(heavy paper clip, or metal
washer), protrator, glue,
scissors, fine-point marker,
atlas.
www.museumoffloridahistory.com/education/resources.cfm