Lunar Observations INTRODUCTION: Over the month one can see changes in the phase of the Moon and when it is visible in the sky ‐ is there a connection? In this lab we will observe the Moon over a period of one month, recording its appearance and position. You will analyze your observations, in groups, and check for patterns, compare them with accepted values, write up the results in a group lab report. Additionally, each student will submit an individual write up answering questions about the lab.
I. MODELING THE PHASES OF THE MOON: The phase of the Moon depends on the angle between the Sun and the Moon as seen from the Earth One half of the Moon is always illuminated by the Sun (unless there’s a Lunar Eclipse), however, the illuminated half is not always fully facing the Earth. (See Figure). As the Moon orbits the Earth we see a different amount of the illuminated side Moon. You can simulate the phases of the Moon using a golf ball for the Moon, a lamp for the Sun and your head will represent the Earth. Hold the ball in front of you so that the lamp illuminates half of it – then turn with the ball still in front so you see a different amount of the illuminated side of the ball. Where are you facing to you see a “Full Ball” or a “New Ball”? Where do you see a “Quarter Ball” Note: when doing this model, assume North is “Up” then the Earth both rotates and spins to the left and the Moon’s orbital motion is leftward (how can you confirm this?). Does the side (East or West) of the Moon illuminated depends on the phase?
II. OBSERVING THE PHASES OF THE MOON 1) On the supplied map of the Moon, find and label the positions of the listed lunar maria, craters, etc. [see http://www.oarval.org/MoonMapen.htm for a labeled map of craters and maria]. Note: when drawing the Moon, you should know the most recognizable features (e.g. Sea of Tranquility, or the Ocean of Storms). 2) During the next month your group will observe the Moon shortly after moonrise (i.e. within 2 hours after moonrise). Fill in the observing sheet: record the date, time, name and location of observer; estimate the altitude of the Moon above the Eastern Horizon, sketch the Moon as it appears, including large features and the terminator (the line separating the bright side from the dark side). In the note section, write the names of lunar features that the terminator passes near or through. Write the Moon’s apparent phase based on its appearance: How much is illuminated and which side is illuminated (see figure above). Each student must do 3 observations; the group must have observations on 12 different days. 3) Measure the altitude and azimuth shift for the rising moon. Start when the Moon is not quite completely above the horizon(it will have an altitude of 0 and an azimuth shift of 0) and continue until the Moon reaches the meridian. This can be done using The Sky software package. Additional instructions will be supplied.
III. DATA ANALYSIS – GROUP REPORT After you have collected your data on the Moon you must analyze it. The analysis will entail making a number of measurements from your drawings and recorded observations. The better quality your observations the easier the analysis will be. These steps should be done in order since some depend on previous steps. You should conduct these analyses and answer the questions in the group lab report. 1) Plot the altitude and azimuth shift of the rising Moon over time. How many degrees per minute does it rise? Is the rate of moonrise constant over six hours? Does this explain why we want to make observations near moonrise? Discuss the plots of altitude and azimuth of the rising Moon, what is the rate of rise for the Moon? How does the azimuth shift over time? Are the rate of rise and rate of azimuth shift constant? Explain your observations using information about the rotation of the Earth and the Moon’s orbit (you may include a diagram if you wish)
2) Using the rate of moonrise from step 1, calculate the time of moonrise for each of your observations. Plot these times along with the published values of moonrise (you can obtain these from software, the internet or newspapers. Eg. http://aa.usno.navy.mil/data/docs/RS_OneYear.html) Refer to your plots: how well do your observations match the published values? What are the minimum, maximum and average errors for your measurements? How much of a difference is there between measurements taken by difference observers on the same day? What does this imply about the accuracy and precision of this measurement? Are these errors acceptable – why do you think so? What could you do to reduce these errors? 3) Estimate the full moon percentage for each observation using the grids on the observing sheet. Each box is 1% of a full moon. Count the number of full boxes, and estimate partially full boxes. The total number will equal the percentage full for each measurement. Plot these times along with the published values of percent full (you can obtain these from software, the internet) Refer to your plots: how well do your observations match the published values? What are the minimum, maximum and average errors for your measurements? How much of a difference is there between measurements taken by difference observers on the same day? What does this imply about the accuracy and precision of this measurement? Are these errors acceptable – why do you think so? What could you do to reduce these errors? Are the errors the same for the percent full and the time of moonrise? 4) Make a table listing moonrise times for this school term for New, First Quarter, Full and Third Quarter Moons. Is this what you expected? Does the time of moonrise vary with the phase? 5) What conclusions can you draw about the time of moonrise, lunar phase and percent full? What were the strengths and weaknesses of the lab for testing the connection between Moon phase and moonrise? How would you improve the lab? Additionally, the lab report must follow the format of lab reports available on my website. It should have all of the sections described. The report must have copies of each observation sheet, and a table of data for the plot. Each data point on the plots should be clearly identified with an observation sheet. More information will be provided.
IV. QUESTIONS TO ANSWER IN YOUR INDIVIDUAL WRITE‐UP: These questions are to be answered by each individual student ‐ discuss each point thoroughly. You may include diagrams or copies of plots from you group report. 1) How much does the time of moonrise vary from one day to the next? Is it always the same amount (hint: check the shape of the moonrise plot – how does it answer this question?). If not what are the minimum, maximum and average amounts? Explain this variation based on the rotation of the Earth and the Moon’s orbit. 2) Is there a moonrise everyday? How do you explain this? (Hint: check around Third Quarter – what happens then?) 3) Which side of the Moon is illuminated (e.g. East or West) for a First Quarter? How about a Third Quarter? Based on your model of Lunar Phases, does this make sense? Explain how you determined if the Moon is waxing or waning on your observation sheet.
Identify the following features on the image of the Moon. For assistance, you may refer to the website http://www.oarval.org/MoonMapen.htm 1 Mare Frigoris (Sea of Cold) 2 Mare Imbrium (Sea of Rains) 3 Sinus Aestuum (Bay of Seething) 4 Sinus Medii (Bay of the Center) 5 Mare Vaporum (Sea of Vapors) 6 Mare Serenitatis (Sea of Serenity) 7 Mare Tranquillitatis (Sea of Tranquillity) 8 Mare Crisium (Sea of Crises) 9 Mare Fecunditatis (Sea of Fecundity) 10 Mare Nectaris (Sea of Nectar)
11 12 13 14 15 16 17 18 19 20
Mare Nubium (Sea of Clouds) Mare Humorum (Sea of Moisture) Mare Cognitum (Known Sea) Oceanus Procellarum (Ocean of Storms) Sinus Roris (Bay of Dew) Sinus Iridum (Bay of Rainbows) Crater Tycho Crater Copernicus Crater Kepler Crater Plato
Moon Observation Sheet (Please make copies: one for each observation) Observer’s Name: __________________________ Date/Time ___________ Location: _________________
Altitude above Eastern Horizon: ________________ Apparent Lunar Phase________________________ Notes: __________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________
Moon Observation Sheet (Please make copies: one for each observation) Observer’s Name: __________________________ Date/Time ___________ Location: _________________
Altitude above Eastern Horizon: ________________ Apparent Lunar Phase________________________ Notes: __________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________