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Observing Project: Observing the Moon
Total Points Possible: 50
Astronomy 311
Due: April 8, 2010
Introduction
You will be observing the moon over the course of the next few weeks in order to become more familiar
with the sky and the motion of the Moon across the sky. You will also become more familiar with the
locations of the constellations and bright stars in your current night sky. You will learn how to roughly
measure the angular distances between objects in the sky as described at the end of this handout.
Thought questions that you should be able to answer, but do NOT need to be included in your report:
1. In your book, review the information about how the moon orbits the Earth. What is the orientation of
the Moon’s orbit to that of the Earth’s orbit around the Sun? With this information, what part of the
celestial sphere (for example, which constellations) would you expect to find the moon over the course
of a lunar cycle?
2. The current lunar cycle began with a new moon on January 15th. Approximately when do you expect
the next new moon to occur? On what date would you expect to see a full moon, first quarter, and
third quarter moons?
3. During what times of the day would you expect to see the first quarter moon?
4. During what times of day would you expect to see the third quarter moon?
5. The moon spends approximately 6.5 days in each of the following phases: waxing crescent, waxing
gibbous, waning gibbous and waning crescent. Would you expect the moon to rise and set at the same
time during those 6.5 days it is in a particular phase? Why or why not?
Read carefully this entire sheet, including the procedure and the questions you need to answer
before starting your project.
Procedure
Record over the period from January 25 to March 19 the position of the Moon with respect to the stars
and constellations, NOT the horizon. For each observation also record the appearance of the Moon, or its
phase. During the course of this period you should make observations on five different days, preferably
on consecutive nights if weather permits. You should have a total of 5 recorded observations.
1. Choose an observing point that allows clear viewing to the east, south and west. You may make your
observations from more than one location and at different times each night.
2. Observe the Moon every clear night it is visible in the evening or morning sky. You need to make
observations on 5 different nights, preferably on consecutive nights if possible. For each night record
the following information:
(A) Date.
(B) Time.
(C) Phase of the moon (sketch and identify)
(D) Mark the location of the Moon with respect to the bright stars and constellations (NOT the
horizon) on the attached sky maps by sketching the appearance of the Moon (phase and
orientation) in its observed location with respect to the stars and constellations.
3. On one night, observe the Moon twice, a few hours apart. Notice how the Moon has moved relative
to reference points along the horizon. You will need this information for one of the
questions. Measure how far the Moon moved over your time interval and calculate about how far and
in what direction the Moon moves in an hour.
4. Once your observations are complete, answer the questions at the end of this page. Show your
work. Your answers should be based on your observations. This means that if your answers are
correct, but not consistent with your sky map, you will not receive full credit. If you believe your
answers using the sky map are incorrect, discuss why you believe this to be true.
5. You will be turning in the following information:
ƒ
A chart with your data recorded on it including the date of observation, time of observation and
sketch of the phase of the moon.
ƒ
Sky map with observations of the moon recorded on it.
ƒ
Answers to questions (on separate page, typed).
Please turn in a neat report (preferably typed) and clearly understandable format. Label all
diagrams. Answer all questions using complete sentences. You will not receive full credit if information
is poorly organized and I cannot discern what observations were made.
Questions (include answers to these in your report):
1. In what direction does the Moon move with respect to the horizon in the course of a few hours? What
causes this motion?
2. In what direction does the Moon move with respect to the stars and constellations from day to
day? What causes this motion?
3. How far in degrees (use your hand as described below to estimate) does the Moon move with respect
to the stars in one day? If you cannot view the Moon on two successive days, divide the distance you
saw the Moon move over several days by the number of days to get its motion per day.
4. Estimate how far in degrees (use your hand as described below to estimate) does the Moon move with
respect to the horizon in one hour?
5. For each of your observations indicate the position of the moon in its orbit by sketching a diagram of
the sun, earth and moon. Also indicate the approximate rising and setting times of each moon as
determined from your diagram. Are the times calculated consistent with your observations? Why or
why not?
Measuring Angles in the Sky
The angular distance between two objects in the sky can be estimated using your hand held at arm's
length. Below is an illustration of the approximate angular size of parts of your hand held at arm's
length. You can test to see how well it does by comparing it to some known sizes. The diameter of the
Moon in the sky is 0.5°, so it should be about half the width of your index finger at arm's length. The
angular separation of Betelgeuse and Rigel in the constellation Orion (see attached star map) is
approximately 18 degrees.
Hints for Observing
1. The New moon will be on February 13, 2010 and on March 15, 2010. You will most likely not be
able to view the Moon in the evening until ~2-3 days on either side of those dates. The moon will be
visible initially in the evening sky, but as we discussed in class, the rise and set times for the moon
change with the changing phases.
2. Use your star charts to find out what constellations are in the sky at the time you go out and observe
the sky. Once you know which constellations the moon is aligned with, you can record that
information on the sky maps.
3. The sky maps are orientated so that if you hold them above your head and line up the cardinal points
(N, S, E, W), you should be able to see the stars listed. I have provided three maps that cover the
portion of the celestial sphere upon which the Moon will be most easily visible at night. You may
record your data on any map. The maps are produced for the times listed on each. For times later or
earlier, the sky will be in different positions because of the rotation of the Earth. You can (and most
likely will) observe at different times than listed on the map, but realize that things will not line up
exactly. As mentioned above, it may be most useful to use the other star-charts to identify the
constellations, and then transfer that information to the sky maps provided.
4. If the Moon appears so bright that it is difficult to view the stars around it, try blocking out the moon
itself with your hand and then letting your eyes adjust to the dark so the fainter stars can be observed.
Good luck! If you any questions, or would like me to look over your observations, I will be happy to talk
with you.
Moon Observation Chart
Date
Time
Moon Phase
Orbit diagram
(name and sketch)
(like Figure 1.17)
E
Sun
Moonrise:
Moonset:
E
Sun
Moonrise:
Moonset:
E
Sun
Moonrise:
Moonset:
E
Sun
Moonrise:
Moonset:
E
Sun
Moonrise:
Moonset: