Lab6
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Louisiana State University *
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Course
1108
Subject
Astronomy
Date
Apr 3, 2024
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10
Uploaded by DukeMandrill1545
1 Name: Astronomy 1108 Lab 6: Lunar Phases Part 1: Objectives After completing this experiment, a student should be able to do the following:
Identify the eight phases of the Moon from a picture
Describe the phase verbally from the name of a phase
Identify the Earth-Sun-Moon geometry for a given phase from the horizon or space view. For example, a student can point to the Sun with one arm and with the other arm point to the approximate location of the Moon.
Given either the phase or the time of rising/meridian/setting, identify the corresponding value. For example, a student can correctly answer what phase of the moon reaches its meridional altitude at about 9 PM?
Estimate the time interval between certain phases
Understand that only (approximately) one side/half of the Moon from Earth
Understand which phase and positions are necessary for solar and lunar eclipses Part
2: Introduction Background information for each of the following subsections can be found under the ‘’Lunar Phases” section in NAAP Labs. The subsections in the lab correspond to the subsections in the application. Read the information in each subsection to answer the following questions. 2.1 Introduction to Moon Phases 1.
Is there a dark side of the Moon? (Note: this question can be effectively answered either yes or no, so it is important to explain the reasoning for the response.)
2 2.2 Moon Geometry 2.
How long does it take the Moon to complete one cycle of phases, in days? 3.
If the Moon if full today, what phase do you expect it to be at in a week? (Names of phases are discussed on the Introduction to Moon Phases page.) 4.
How about one month from today? 5.
Figure 1 shows the Moon’s appearance made over about four weeks. Identify the phases and put them in the correct numerical order. One has already been properly labeled. Figure 1: The Moon’s appearance during a four-week period. 6.
From the perspective of an observer above the North Pole, does the Moon move clockwise or counter- clockwise in its orbit around the Earth?
3 7.
In the figure below, the Sun’s light is coming in from the right. The moon’s location is marked at several points on its orbit. These are the points the Moon was at when the sketches in Figure 1 were drawn. Identify each position with the letter
of from question 5. Figure 2: The positions of the Moon during certain times in its orbit. 2.3 Time of Day Use the interactive diagram at the bottom of the section to determine the direction of the Earth’s rotation when viewed from above the North Pole. (Hint: rotate the observer – the stick figure – to the noontime position, then sunset position, then midnight position, and finally back to sunrise position. The Earth has made one complete rotation and the observer has experience one daily (diurnal) cycle of day and night.) 8.
When viewed from above the North Pole, does the earth rotate clockwise or counter- clockwise over time?
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4 2.4 Rising & Setting 9.
When the moon crosses the western side of the horizon plane is it rising or setting? When it crosses the eastern side of the horizon plane is it rising or setting? 2.5 The Horizon Diagram 10.
Describe the location of the Moon in the sky of the horizon diagram at the bottom
of the section. Use direction words (like north, west, etc.) and estimate its altitude in degrees. 2.6 The Witness and the Detective 11.
If the Moon’s position in the sky and its phase are known, ____________ can be estimated. In general, knowing any two of the following three things allows for the estimation of the third.
Moon’s position in the sky
______________________
______________________
5 Part 3: Moon Bisector Demo 12.
The appearance of the Moon based on the orientation of the Moon and Sun can be determined with a simple activity. In the figure below, bisect the Moon twice
:
Draw a line (perpendicular to the direction of sunlight) that shows the half of the entire Moon that is illuminated and shade the shadowed region.
Draw a line (perpendicular to the Earth-Moon line) that shows the half of the moon visible for an observer on Earth.
Mark the region that both visible from Earth and illuminated by the Sun. That region will be the phase of the Moon seen by the Earth. Figure 3: Diagram of showing the position of incoming sunlight, the Earth, and the Moon at a particular time in the Moon’s orbit. Normally phases of the Moon are drawn with the terminator (the dividing line between light and shadow) from the north pole to the south pole of the Moon. This is how the Moon would be seen if it were on the observer’s meridian. 13.
Fig 3 can be used to determine the amount of illumination and whether it is on the left- or right-hand side of the Moon. Use Fig 4 to draw the appearance of the Moon as it would appear in Fig 3. Figure 4: A blank area to draw the appearance of the Moon as seen from Earth given the configuration of Fig 3. Open the Moon Bisector Demo and use the simulator to check the answer to the above problem.
6 Part 4: Lunar Phase Simulator The items below will help familiarize the controls and usability features of the simulator.
The main panel has sunlight, the Earth, and Moon. The Earth and Moon can be dragged with the mouse.
Below the main panel, there are animation controls. The Earth and Moon can be dragged.
The increment button moves both the Earth and Moon by the specified time.
The Moon Phase panel shows the current Moon phase. Drop down menus will jump to a predefined position. Note that the phases, such as crescent and gibbous, are broader than the particular point chosen by the presets.
The Horizon Diagram panel displays the point of view of the observer from the orientation of looking down on that observer.
The observer’s horizon diagram can be dragged to allow for the most convenient viewing orientation.
The Sun and Moon on the globe can be dragged around.
In the Diagram Options panel, the show angle
option shows the Earth-Moon-Sun angle. The phases are technically defined in terms of this angle.
in the Diagram Options
panel, the show lunar landmark
option draws a point of reference to more easily observe lunar rotation and revolution.
In the Diagram Options
panel, the show time tick-marks
option displays the time of day of the observer. 4.1 Earth-Moon-Sun Geometry Within the Lunar Phase Simulator, click on the option labeled show angle - which graphically displays the angle between the direction of the Sun and Moon. Now drag the Moon around the Earth to a variety of different locations and note the appearance of the Moon phase. 14.
Describe how the value of the angle correlates with the appearance of the Moon.
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7 4.2 Rising, Setting, and Meridian Times When observing the Moon, one thing to know in advance is when it is visible – what time it sets, rises, and crosses the meridian (or transits). The applet can help find these times. Example 1
: What is the meridian crossing (transit) time for the new moon? Move the Moon to its New Moon position. Rotate the Earth until the moon is centered on the meridian (the observer should be located on the Earth directly opposite the Moon). For finding transit times it helps to change the perspective of the horizon diagram (by clicking on and dragging it) so that we are looking straight down on the diagram. Note that the transit time of the New Moon is 12:00 PM (noon). Example 2
: What is the setting time for a Full Moon? First move the Moon to the Full position by dragging it, or selecting ‘’Full Moon” in the Moon Phase drop down list (upper right). Next, click on and rotate the Earth while keeping an eye on the horizon diagram in the lower right corner. Rotate the Earth until the Moon just disappears below the western horizon. Verify that this occurs at 6:00 AM. 15.
Complete the rest of the rising, meridian crossing, and setting times in Table 1. Phase Rising Meridian Crossing Setting New 12:00 PM Waxing Crescent First Quarter Waxing Gibbous Full 6:00 AM Waning Gibbous Third Quarter Waning Crescent Table 1: Timings of the Moon 16.
Describe the relationship between the values of the meridian times and the rising and setting times in Table 1.
8 Part 5: Lunar Phases and the Horizon Diagram This module contains a simulator especially for gaining insight into the lunar phases in the horizon system. Please load the Moon Phases and the Horizon Diagram simulator. Follow the guidelines below to gain familiarity with the simulator. Please begin by unchecking all options.
Click the option entitled show ecliptic band
. Since the ecliptic can be as much as 23.5
◦ away from the celestial equator and the plane of the Moon’s orbit is inclined almost 6
◦ to the plane of the ecliptic – the Moon can be in a band almost 60
◦ wide in the sky. For this lab, it is assumed that the Moon is always located on the celestial equator. Unclick show ecliptic band.
The sun position setting identifies 8 distinct locations for the Sun corresponding to 8 distinct times. Click show Sun and show time and use the slider to manipulate the Sun’s position. Place the Sun at the appropriate location for each of the following times: 6 am, 9 am, noon, 3 pm, 6 pm, 9 pm, midnight, and 3 am.
Place the Sun at the noon position (position 3). Click show Moon and place the Moon at position 3 as well. Click show phase and show phase on Moon disc
. Now step through the 8 possible positions. Note that when the Moon is one position east of the Sun, its phase is waxing crescent. When the Moon is two positions east of the Sun its phase is first quarter. Move the Moon through the remaining phases of the cycle. Thus, there are two general rules for solving problems in the horizon system.
The time is denoted by the position of the Sun.
The phase of the Moon is denoted by how many (out of the 8 steps) the Moon is east of the Sun.
9 17.
Complete Table 2. Visualize the solutions in horizon diagrams drawn on scratch paper and then use the simulation to check the answer. Time Phase Location A Noon First Quarter B 3 PM First Quarter C First Quarter Western horizon D 9 PM Waning Gibbous E 3 AM Southwest F Midnight Waxing Gibbous G Waxing Crescent Southeast Table 2: Location and Phase based on Time Close the Moon Phases and the Horizon Diagram Simulator and return to the Lunar Phase Simulator and answer each of the following questions. 18.
Figure 5 (on the next page) shows the Moon and Sun on a horizon diagram. What is the phase and what is the time of day depicted? What time did the Moon reach its highest point in the sky? (Hint: Use the increment animation controls.) 19.
In Fig 5, draw and label the Moon’s location 48 hours later. Will the Moon be visible at noon 14 days later? Explain your answer. (Hint: Use the increment animation controls.)
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10 Figure 5: The Moon and Sun displayed in relation to a horizon. 20.
Draw and label the Full Moon and Sun at 6 am on Fig 6. (if necessary or useful, draw an arrow to one or both spots) Figure 6: A blank horizon diagram.