RANDY L. PHELPS

This is the "Determining Your Latitude" Exercise

The following Applet was written and provided by Walter Fendt and is copyrighted by him.  The right of commercial use remains with that author.

Purpose: The purpose of this exercise is to illustrate the differences in the sky as observed from various locations (latitudes) on the Earth.   By changing the latitude interactively, the student should see the correlation of the observed sky with the observer's latitude.  The student should also see how, by observing the altitude of the celestial pole, the latitude from which the observations are made can be determined.

Procedure:

  • Recall what the definition of latitude is: Latitude is the angle, as measured from the center of the Earth, between the Earth's Equator and another location on the Earth's surface.
  • Do each  "Exploration " outlined in the first column below.  Before you actually do each "Exploration", answer the questions posed in the "Anticipate the Result" box for that "Exploration".  After you have done this, determine if the actual result was as you expected, or somehow different.  If the actual result was different, determine why before you proceed to the next step.
  • At the end of the exercise, you should have answered the "Anticipate the Results" questions, which are also many of those that appeared in the lecture note portion of this module.

Exploration

 Anticipate the Results Instructions/Sugestions to Help Answer These Questions
1. The Appearance of the Sky at the North Pole of the Earth

 

 

 

 

 

 

 

 

 

 

 

 
  • Where is the North Celestial Pole as seen by an observer at the North Pole?
  • Where is the Celestial Equator as seen by an observer at the North Pole?
  • What star should be located near the zenith?
  • What is the altitude of the North Celestial Pole at the Earth's North Pole?
  • What is the latitude at the North Pole?

 

 

 

 

 

 

 
  • On the figure on the left hand side below, place the cursor at the point where the arrows intersect, which is on the circle representing the Earth's surface. The arrows indicate the directions, as seen by you on the surface of the Earth, to the North Celestial Pole, the zenith, and your northern and southern horizons.
  • While holding down the left mouse button, move the cursor to the desired location on the Earth's surface.  In other words, move the cursor to place the observer at the North Pole.
  • Note as you move the cursor (your observation point), the direction to the North Celestial Pole does not change, but the angle between the Celestial Pole and your horizons does change.
  • Note how the view of your sky, illustrated in the right-hand figure, appears at this new location.
2. The Appearance of the Sky at the Equator of the Earth

 

 

 

 
  • Where is the North Celestial Pole as seen by an observer at the Equator?
  • Where is the Celestial Equator as seen by an observer at the Earth's Equator?
  • What is the altitude of the North Celestial Pole at the Earth's Equator?
  • What is the latitude at the Earth's Equator?
  • Repeat the procedure outlined in Exploration 1, but this time move the cursor   to place the observer at the Earth's Equator.
  • Note how the view of your sky, illustrated in the right-hand figure, appears at this new location.

 
3. The Appearance of the Sky at an intermediate latitude on the Earth

 

 

 

 
  • Where is the North Celestial Pole as seen by an observer at an intermediate latitude?
  • Where is the Celestial Equator as seen by an observer at an intermediate latitude?
  • How does the altitude of the North Celestial Pole change as  the latitude changes from 0o to 90o?
  • What would the altitude of the North Celestial Pole be here in Sacramento?
  • Repeat the procedure outlined in Exploration 1, but this time move the cursor   to place the observer at an intermediate latitude on the Earth's surface..
  • Note how the view of your sky, illustrated in the right-hand figure, appears at this new location.

 

 

 

Critical Thinking/Applications: 

Now try to explore the following.  First think about the question, and then determine what parameters in the applet need to be changed to help you explore the concept.  

Exploration

 Anticipate the Results Instructions/Sugestions to Help Answer These Questions
N/A

Not yet implemented

Not yet implemented