X. Plotting the Moon’s (or Sun’s) Orbit.

1. This project will take a few minutes each night for a month. Obtain a star chart from your instructor or make your own if you feel confident in doing that. (There is an option of observing the Sun’s motion listed below too.)
2. Once each night carefully record the position of the Moon on your star chart. Note that during part of the month you will need to do this in the evenings and part of the month in the early mornings. You will need to make very careful measurements of the Moon. You will need to do triangulations to get the position of the Moon correctly. Measure the position of the Moon in degrees of arc from three bright stars and then use a drawing compass to record the exact position of the Moon on your star chart. See Figure 1 on page 2 for hints on how to measure angles in the sky using your hands. See your instructor for more details on how to triangulate the position of the Moon on your chart. See your instructor for other hints and suggestions.
3. Describe the motion of the Moon. How many days does the Moon take to get back to the same position relative to the stars? (I.e., what is the period of the Moon’s orbit?) What direction (East or West) does the Moon move relative to the background stars? How many degrees the does the Moon move in 24 hours relative to the background stars?
4. As an alternative you can plot the Sun’s apparent motion against the background stars as caused by our point of view from Earth orbiting the Sun. This is a bit more challenging since you will have to estimate where the Sun is after sunset and once enough stars appear to plot against. You will need to make measurements about once a week for about two months to complete this option. See your instructor for help and hints if you’d like to try this observing option. This sort of thing was done by ancient astronomers thousands of years ago.