Mapping the Orbit and Phases of the Moon

Summary: Track the phases and measure the orbital period of the moon, and measure the angle between the plane of the moon's orbit and the ecliptic plane.

General Description Look up! Observe the moon. Hints: if the moon is near 1st quarter or full moon phase, you will be able to make your observations in the early or late evening. If the moon is past full moon or near 3rd quarter, you will have to make your observations either very late at night or in the early morning. Your logs should include at least two observations of the moon during daylight hours, one before 12:00 noon; one after 12:00 noon).

Determine the approximate position of the Moon with respect to the stars and constellations you can identify. Determine the phase of the moon at this time.

Plot this position on your star chart by sketching the moon in its approximate phase at the correct location relative to the stars.

Measure the angular size of the Moon when it is full, using the fist and finger rules (see Appendix A of your ClassPak).

Keep an observing log, recording the time, date, weather conditions, phase of the moon, and the constellation in which the Moon appears. (For daytime observations, you won't be able to determine the constellation.)

6. Answer the following questions:

a) Write a brief summary describing the changes you observed in the phase of the moon. Your summary should include the times of the day (or night) when you would now expect to observe a 1st quarter moon, full moon, 3rd quarter moon, and new moon.

b) What is the period for the completion of one cycle of lunar phases, as determined from your measurements?

c) Why does the moon go through phases?

d) Describe the orbital path of the moon through the stars. What constellations does it pass through? What does this path tell you about the moon's orbit, as compared to the orbital plane of the earth around the sun (the ecliptic)?