1. Human Understanding of both Earth and Space has Changed Over Time
Unit E: Topic One

2. 1.5 Describing the Position of Objects in Space

3. Frames of Reference

4. Frames of Reference
A frame of reference is a set of axes used to describe positions or motions of things.
The stars, the Sun and the planets do not rotate around the Earth, but seem to because the Earth is rotating on its axis.
The Earth is our fixed frame of reference.
On Earth, the equator and the prime meridian (latitude and longitude) are the axes used.
But the motion of objects depends on your frame of reference.

6. Frame of reference worksheet

7. Stars as a Frame of Reference
Ancient cultures tried to explain the motions of the stars and planets, with their frame of reference being the Earth.
To track the actual motion of each celestial body in space, you need to use the stars as your frame of reference.
To do this:
make an observation of which celestial body you are studying
include other stars in relation to it
make subsequent observations and include those same stars
Over a period of time you would be able to determine in which direction the celestial body you are studying is moving.

8. Altitude and Azimuth

9. Where in the sky is it?
But how did they measure locations of celestial bodies in the sky?
In order for scientists to understand the sky and what was going on, they had to observe, measure and calculate.
To document the location of an object, scientists use altitude, azimuth and altitude-azimuth coordinates.

10. Altitude
Altitude gives you the “how far above the horizon it is”. (0º to 90º)
Stars straight up will be at 90º
Points on the horizon will be at 0º
Stars half way up the sky
will be at 45º
Zenith refers to the
highest point directly
overhead

11. Azimuth
Azimuth determines which compass direction it can be found at in the sky. ( in degrees from 0º to 360º )
Stars in the north will have an azimuth of 0º
East = 90º
South = 180º
West = 270º
(clockwise)

13. http://astro. unl. edu/classaction/animations/coordsmotion/altazimuth

14. Determining Motion of Objects in Space
Planet means “wanderer” in ancient Greek
The path in the sky along which the Sun takes is called the ecliptic.
The Celestial Sphere is the name given to the very large imaginary ‘sphere of sky’ surrounding the Earth.
Celestial equator is directly
above the Earth’s Equator

15. Activity: Altitude and Azimuth
Note the star up in the corner of the room.
Extend one arm out in front of you and make a fist. Close on eye and practice aiming along your arm so you can see the star.
Start with one arm held horizontal to the floor.
From your desk – estimate how many fists you need to “climb” to the object.
Each fist is 10 degrees – Record how many degrees the altitude of the star is from your desk.
Next estimate the compass direction. Use the compass directions given. Record the azimuth.
Compare with your neighbour.

16. There are 5 hanging objects in the classroom
There are 5 hanging objects in the classroom. Describe their coordinates using altitude and azimuth.   Show your data in a table for azimuth-altitude:
Coordinate
Object 1
__________
Object 2 __________
Object 3 __________
Object 4 __________
Object 5 __________
Altitude
Azimuth

17. Discussion Questions What similarities did you notice in your results?
What differences?
What was the accuracy of your results?
Explain why you might have gotten a different result from a nearby student.
Explain why you might have gotten a different result from a student farther away.