# Development of a Lunar-Phase Observation System Based on Augmented Reality and Mobile Learning Technologies

Authors: Wernhuar Tarng; Yu-Sheng Lin; Chiu-Pin Lin; Kuo-Liang Ou
Journal: Mobile Information Systems
 (2016)

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## Abstract

Observing the lunar phase requires long-term involvement, and it is often obstructed by bad weather or tall buildings. In this study, a lunar-phase observation system is developed using the augmented reality (AR) technology and the sensor functions of GPS, electronic compass, and 3-axis accelerometer on mobile devices to help students observe and record lunar phases easily. By holding the mobile device towards the moon in the sky, the screen will show the virtual moon at the position of the real moon. The system allows the user to record the lunar phase, including its azimuth/elevation angles and the observation date and time. In addition, the system can shorten the learning process by setting different dates and times for observation, so it can solve the problem of being unable to observe and record lunar phases due to a bad weather or the moon appearing late in the night. Therefore, it is an effective tool for astronomy education in elementary and high schools. A teaching experiment has been conducted to analyze the learning effectiveness of the system and the results show that it is effective in learning the lunar concepts. The questionnaire results reveal that students considered the system easy to operate and it is useful in locating the moon and recording the lunar data.


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## Body

## 1. Introduction

Astronomy is an important area of natural science because its scope ranges over the stars and materials in the universe, including all celestial bodies and their interaction as well as our living environments. The changes of celestial phenomena have a great influence on our daily lives. Thus, observing the motion of celestial bodies such as the sun, the moon, and stars has been an essential part in astronomy education. In addition, astronomical observation can motivate students to develop creativity and independent thinking by using scientific methods and inference skills to solve the problems and derive correct answers.Observing celestial bodies is an important topic in K12 science and technology curriculums. Students may think of celestial motions by observing the sun, the moon, and stars and then use scientific methods to induce the rules and causes of their interaction. Therefore, the observation and investigation processes can enhance the critical thinking and problem solving abilities of students. The moon is the nearest celestial body to the earth, so it is a suitable target for observation. By doing so, students can realize that the lunar phase is periodic after observing the moon in a regular and long-term manner. They may discover the relative motion of the sun, earth, and moon by observing the rising and falling of the sun and the moon. Alternatively, students can also understand the cause of lunar phases, solar and lunar eclipses, day and night, and the four seasons by operating the 3D model of these celestial bodies.Observing the lunar phase requires long-term involvement, and it is difficult when encountering the following situations: (1) a bad weather often upsets the observation plan; (2) tall buildings in metropolitan areas may obstruct observation; (3) impatient students sometimes fail to keep complete records of the lunar phase; (4) students often fall asleep when the moon appears late at night. Besides, it is difficult for students to infer that the lunar phase is regular and periodic from the recorded data, especially when the data are not complete. All these factors prevent them from developing correct concepts.In addition to the difficulty in lunar observation, students often presume the motion of the sun, earth, and moon in a subjective manner, and even their science teachers may have misconceptions [1]. Besides, a lot of elementary school students lack spatial concepts, and their cognition has not reached the formal operation stage [2]. If the learning activity is only for a short term without completing the whole observation process, students are unlikely to obtain correct lunar concepts.To enhance the understanding of scientific concepts, 3D models are often designed to simulate the natural phenomena which are difficult or impossible to observe in the real world [3]. Because computer simulation presents a simplified and visible model for the situations mentioned above, it can attract learners’ attention and provide them with concrete concepts about the simulated phenomena [4]. Researchers have reported the success of computer simulation in supporting inquiry and reasoning skills [5, 6]. Winn et al. [7] asserted that computer simulation has the potential to promote cognitive development and conceptual change more effectively than direct experiences. Thus, how to develop effective simulation software to assist students in learning science is a research topic worth investigation.Recently, many studies are focused on learning astronomical concepts using simulation software developed with friendly user interface for simulating celestial phenomena. The software enables its users to observe the virtual sky and search for celestial objects, for example, Starry Night [8] and Google Sky Map [9]. Tarng and Liou [10] developed a web-based astronomy museum using the virtual reality (VR) technology for applications in elementary science education. Hobson et al. [11] discovered that it is effective to teach lunar concepts using simulation software for 2nd and 3rd grade students. Trundle and Bell [12] studied the effectiveness of integrating simulation software with inquiry-based instruction to enhance the lunar concepts of preservice teachers. Sun et al. [13] proposed a 3D virtual reality model of the sun and the moon for e-learning at elementary schools. The experimental results show that students’ learning achievement is higher than that of using the traditional class instruction.Although the available lunar simulation software is effective, a gap still exists between its operation and actual observation. Consequently, students may have difficulty applying their operational experiences on computers to real observation. For instance, they do not need to know the azimuth and elevation angles when operating the simulation software on desktop computers. Moreover, the motion in real observation such as raising hands for measuring the elevation angle and lifting head for finding the moon is replaced by operating the mouse and keyboard. Without physical operation and sensory integration, students may have a hard time adjusting to outdoor observation. Besides, there are no familiar objects on the ground to serve as reference points when using simulation software and students cannot develop the ability of measuring the direction and elevation angles in real observation.The lunar phase changes as the moon revolves around the earth, and the latter also revolves around the sun while rotating by itself, all counterclockwise. Therefore, spatial concepts play an important part to affect students in learning lunar concepts. Traditional teaching materials cannot provide students with an effective method for obtaining correct lunar concepts, so students lacking spatial concepts may have difficulty learning the cause of lunar phases by observing the relative motion of the sun, earth, and moon. If the simulation software allows students to observe the moon in the sky and record the lunar phase and the related data easily, it can also be used to show the lunar phase according to the relative positions of the sun, earth, and moon and help students understand the cause of lunar phases.As the advance of information technology, mobile devices such as the personal digital assistant (PDA), smart phone, and tablet PC are integrated into educational applications. As a result, learning activities are no longer confined to classroom teaching, and they can be done anytime and anywhere using any devices to achieve the goal of ubiquitous learning [14]. Mobile learning refers to any forms of learning which takes place when a learner is on the move or can move to a new place and still remain connected to online learning resources through wireless networks. Recently, a large number of mobile devices are equipped with powerful sensors such as the GPS, electronic compass, and 3-axis accelerometer to provide the information of position, time, direction, acceleration, and so on to support the design of simulation software for applications in different areas of education.Augmented reality (AR) is a view of the real world where elements are augmented by computer-generated situations or objects to enhance one’s perception of reality. In this way, the information in real environments becomes interactive and can thus be manipulated digitally and physically. Besides, artificial information about the environments and virtual objects can also be overlaid in the real world. According to Azuma [15], AR is an evolution of virtual reality (VR) with the following features: (1) interacting with real and virtual environments, (2) providing real-time feedback, and (3) having to be in 3D space. Compared with the operation of VR, AR integrates a real environment with virtual objects to enhance one’s comprehension and the sense of reality in a more interactive way. Recent research has shown that applications of AR in learning activities can improve students’ knowledge construction and engage learners in high flow experience levels [16–18]. Therefore, it can be used as an effective tool to promote science learning [19–22].In general, the implementation of AR can be categorized as (1) the traditional AR, which requires a marker for positioning, for example, the Magic Book [23], (2) the AR without a marker, in which positioning is done by GPS or image detection, and (3) the AR combining a marker and image detection for positioning. AR can increase interaction with the real world and provide useful information not directly available. This study is aimed at applying AR and mobile learning technologies to develop a lunar-phase observation system. The main objective is for the user to see the virtual moon by holding the mobile device towards the real moon even if it is obstructed by a bad weather or tall buildings. Also, the lunar phases can be recorded for displaying the moon’s track and the relative positions of the sun, earth, and moon to study the cause of lunar phases.In 1970, the concept of context awareness was proposed by United States Department of Defense using GPS to obtain the user’s location for providing various services [24]. Its main idea is to satisfy the user’s sensational requirement by updating necessary information according to environmental changes such as the time and position [25]. The theory of situated learning [26] emphasizes that learning is unintentional and knowledge has to be presented in real situations. Its main idea is to provide a realistic environment for learners and the acquired knowledge can be applied in a similar context. Therefore, if learners wish to construct knowledge about lunar concepts, they should deal with the situations that occurred in the real world. By doing this, the obtained knowledge is more meaningful and thus can be applied in practical situations.Based on the modes of representation proposed by Bruner [27], the initial phase of the cognitive process is enactive representation, where learners integrate actions into cognition in order to learn by doing. Moreover, they may turn the outside world into images, signs, and symbols to interpret the obtained knowledge in an abstract or a logical way. In this way, learners can understand and acquire knowledge easily and store it in long-term memory, which may enable them to learn better in the future and develop the transfer of learning. According to relevant studies [28, 29], it was discovered that actions can attract learners’ attention and enhance their learning. Thus, it is believed in this study that the integration of AR and physical operation in observing lunar phases can help students develop lunar concepts and store in long-term memory to make learning more effective.Currently, mobile applications for learning lunar concepts are mainly focused on the display of lunar phases. For example, Lunafaqt [30] allows its users to see the instant lunar phase and also for the entire month based on current (or input) date, time, and location. Among the applications in astronomy education, Google Sky Map allows the user to set a different date, time, or location for displaying the moon in addition to the celestial bodies such as constellations and planets as well as some astronomical phenomena. However, these two applications are not designed for learning lunar concepts and neither can they record the data of lunar phases such as the lunar calendar, azimuth, and elevation angles. Moreover, they cannot display the moon track in the sky and the lunar phases according to the relative positions of the sun, earth, and moon using the recorded data to help the user understand the cause of lunar phases.In this study, a lunar-phase observation system is developed using the AR technology and sensor functions of GPS, electronic compass, and 3-axis accelerometer on mobile devices to help students observe and record lunar phases. When the user holds the mobile device towards the moon’s position, the screen will show the virtual moon overlapping the image of real moon (Figure1). The compass will show the azimuth of the moon and its elevation is obtained from the 3-axis accelerometer and listed on top of the screen. The system allows the user to record the lunar phase and its azimuth/elevation angles as well as the observation date and time. The system can shorten the learning process by setting different dates and times for observation, and it can solve the problem of being unable to observe and record lunar phases due to bad weather or obstruction by surrounding tall buildings. In addition, the physical operation in observation can leave a deeper impression on learners to store the obtained knowledge in long-term memory. A teaching experiment has been conducted to investigate the learning effectiveness of elementary students by using the lunar-phase observation system as a tool for learning lunar concepts. A questionnaire survey has been conducted to analyze the attitudes of students after using the system, and the results can also be used as a reference for improving the system.Figure 1
The lunar-phase observation system.


## 2. System Design

The lunar-phase observation system is developed using Shiva3D and 3ds Max based on the data obtained from Taipei Astronomical Museum. In addition, the tools of JDK, Android 1.5 SDK, Eclipse, and Android Development Tool Plug-in are also required for programming the sensor functions of GPS, electronic compass, and 3-axis accelerometer on mobile devices. After the system is completed, Shiva3D’s Authoring Tool is used to convert it into the installation (APK) file for uploading to Google Play. The testing environment is Android 4.0 installed on an ASUS tablet PC. The system modules include the 3D model of the sun, earth, and moon (for calculating the moon’s position), camera control and time control, interactive user interface, GPS, electronic compass, 3-axis accelerometer, and API programs (Figure2). The camera is used to observe the moon in the sky to verify the correctness of the virtual moon’s position. However, the system can still be used if the real moon cannot be seen due to a bad weather condition. To record the lunar phase, the user simply holds the mobile device towards the moon’s direction until its image overlaps the virtual moon on the screen. A red circle will appear to surround the virtual moon and then the user can press the button to record the lunar phase and its data.Figure 2
The architecture of the lunar-phase observation system.


### 2.1. 3D Model of the Sun, Earth, and Moon

The 3D model of the sun, earth, and moon is developed according to their rotation periods and revolution periods and controlled by the equation about planetary motion (i.e., Kepler’s second law) which governs the earth’s revolution around the sun and the moon’s revolution around the earth. To simplify the design process, we set the sun’s position at the center of this model. In fact, the sun situates at a focal point of the earth’s elliptic orbit and revolves around the center of the Milky Way galaxy by a period of approximately 200 million years. As we only consider the relative motion between the earth and the sun, using a simplified model can reduce the computation time in coordinate transformation between these complicated coordinate systems.To calculate the rotation angle of the earth model per unit time, we must know the time required for the earth to rotate once (360 degrees). Traditionally, a day (or solar day) is defined as the time between two successive transits of the sun across the meridian, which is divided into 24 hours. However, the angle that the earth rotates for a solar day is slightly greater than 360 degrees because the earth is also revolving during its rotation. The time for the earth to rotate 360 degrees (also defined as a sidereal day) can be calculated as follows. Since the earth makes a revolution around the sun in a year (365.24 days), each solar day the earth must turn about an additional degree to see the sun on meridian. Therefore, it takes about 24 × 60/361 = 4 minutes for the earth to rotate one degree, so a sidereal day is only about 23 hours and 56 minutes.The moon is the nearest planet to the earth, and its average distance to the earth is 384,400 kilometers, about 60.3 times the earth’s radius. The moon is the satellite of the earth, and its mass is about 1.2% that of the earth. The moon revolves around the earth and thus they also revolve around the sun together. By observing the change in lunar phases, the interval between two full moons is approximately 29.5 days. Using the same method to calculate a sidereal day, we derive that the moon takes 27.3 days to revolve 360 degrees. As a result, the time for the moon to rotate one degree is about 24 × 27.3/360 = 1.8 hours. Because the moon’s rotation and revolution periods are the same, we can only see the same face of the moon from the earth.The moon revolves counterclockwise around the earth along its orbit, which does not overlap the ecliptic plane but is tipped by an angle of 5°9′. Also, the axis of the earth model is rotated by an inclined angle of 23°27′ between the orbital plane and the equatorial plane. As the moon spins on its axis, the axis itself wobbles like a gyroscope and its rotation period is about 18.6 years. Therefore, the moon’s position in the sky is between 28°36′ south and 28°36′ north of the equator (Figure3). We can derive the moon’s position in the earth-based and the sun-based coordinate systems after the earth’s position has been determined.Figure 3
The coordinate systems of the sun, earth, and moon.The 3D model of the sun, earth, and the moon for displaying their relative motion and lunar phases can be developed by the computer simulation (Figure4). We have designed the control program using Shiva3D, which obtains the current time from system API programs to determine the positions and rotation angles of the earth and the moon in the sun-based coordinate system. Then, we rotate the earth model and the moon’s revolution orbit by their inclined angles. Finally, the center of the moon’s revolution orbit is transformed to the earth center such that both their positions are calculated in the sun-based coordinate system. After the new positions of the moon and earth have been obtained, their rotational angles must also be computed before the rendering process takes place. We set up two cameras, one from the outer space and the other at the user’s GPS coordinates on the earth model, to display the motion of earth and the moon as well as the change of lunar phases.Figure 4
The 3D model of the sun, earth, and moon.The completed lunar-phase observation system can be executed on Android mobile devices. Science teachers can download it from Google Play and install on their smart phones or tablet PCs for teaching applications. The system is designed based on the learning units of “Lunar phase observation” and “The sun, earth, and moon” in K12 Science and Life Technology Curriculum [31] for 4th and 9th graders, respectively. The objective of the former is to understand that the lunar phase is periodic by observing the moon in a long-term and regular manner; the objective of the latter is to discover the rising and falling of the moon and the change of lunar phases by the relative motion of the sun, earth, and moon.After starting the system, the user can see the main menu, including the buttons of Observe Lunar Phase, Record Lunar Phase, and Exit (Figure5). The system is designed with five major functions: (1) locating the moon and displaying its lunar phase, (2) setting the system date and time, (3) recording the lunar phase, (4) displaying the moon track, and (5) showing the lunar phase according to the relative position of the sun, earth, and moon. At the beginning, the system obtains the data of current position (from GPS) and date and time (from API). By clicking the button Observe Lunar Phase, the system will activate the electronic compass and 3-axis accelerometer to measure the azimuth and elevation angles of the mobile device.Figure 5
The main menu of the lunar-phase observation system.


### 2.2. Locating the Moon

The system uses a blue arrow to indicate the moon’s direction in the sky (Figure6). As soon as the moon is located, a red circle will appear to surround the moon (Figure 7). After that, the user can click the Record Lunar Phase button to record the lunar phase and its relevant data. The user can also click the Record Data button to check the recorded data. To prevent from pressing the button accidentally, the system can only record the lunar phase when the moon is inside the red circle. Also, it will show the message “Success” or “Failure” to notify the user if the lunar phase is recorded successfully or not.Figure 6
The arrow showing the moon’s direction.Figure 7
Locating the moon inside the red circle.


### 2.3. System Date and Time

The user can change the system date and time by clicking the Set Date and Set Time buttons, and the current time can also be restored by clicking the current time button (Figure8).Figure 8
Change the system date and time.


### 2.4. Recording the Lunar Phase

By clicking the Record Data button on the main menu, the user can record the lunar phase hourly or daily and the system will record the lunar phase and its relative information, including azimuth angle, elevation angle, date, time, and position, accordingly (Figure9). After recording the data, the user may convert them into organized and meaningful information with the functions of displaying the moon track in the sky and showing lunar phases according to relative positions of the sun, earth, and moon to help the user understand the lunar concepts.Figure 9
Recording the lunar phase and its relative information.


### 2.5. Displaying the Moon Track

By clicking the button of Display Moon Track, the system will show the lunar phases by the order of recorded times in one day (Figure10). When clicking the data displayed on top of the screen, the user will see the corresponding lunar phase shown in Figure 10. This function allows the user to see the different positions of the moon in the sky and the variation of its azimuth and elevation angles as time changes.Figure 10
Displaying the moon track in the sky.


### 2.6. Cause of the Lunar Phase

The system has a built-in 3D model to simulate the relative motion of the sun, earth, and moon, which can be used to illustrate the cause of lunar phase (Figure11). By clicking the Start button, the system will apply the recorded data to the 3D model to demonstrate the cause of lunar phases with the perspective view from the outer space. The user can see the relative positions of the three planets and the corresponding lunar phase and its related data.Figure 11
The 3D model to demonstrate the cause of lunar phases.


## 2.1. 3D Model of the Sun, Earth, and Moon

The 3D model of the sun, earth, and moon is developed according to their rotation periods and revolution periods and controlled by the equation about planetary motion (i.e., Kepler’s second law) which governs the earth’s revolution around the sun and the moon’s revolution around the earth. To simplify the design process, we set the sun’s position at the center of this model. In fact, the sun situates at a focal point of the earth’s elliptic orbit and revolves around the center of the Milky Way galaxy by a period of approximately 200 million years. As we only consider the relative motion between the earth and the sun, using a simplified model can reduce the computation time in coordinate transformation between these complicated coordinate systems.To calculate the rotation angle of the earth model per unit time, we must know the time required for the earth to rotate once (360 degrees). Traditionally, a day (or solar day) is defined as the time between two successive transits of the sun across the meridian, which is divided into 24 hours. However, the angle that the earth rotates for a solar day is slightly greater than 360 degrees because the earth is also revolving during its rotation. The time for the earth to rotate 360 degrees (also defined as a sidereal day) can be calculated as follows. Since the earth makes a revolution around the sun in a year (365.24 days), each solar day the earth must turn about an additional degree to see the sun on meridian. Therefore, it takes about 24 × 60/361 = 4 minutes for the earth to rotate one degree, so a sidereal day is only about 23 hours and 56 minutes.The moon is the nearest planet to the earth, and its average distance to the earth is 384,400 kilometers, about 60.3 times the earth’s radius. The moon is the satellite of the earth, and its mass is about 1.2% that of the earth. The moon revolves around the earth and thus they also revolve around the sun together. By observing the change in lunar phases, the interval between two full moons is approximately 29.5 days. Using the same method to calculate a sidereal day, we derive that the moon takes 27.3 days to revolve 360 degrees. As a result, the time for the moon to rotate one degree is about 24 × 27.3/360 = 1.8 hours. Because the moon’s rotation and revolution periods are the same, we can only see the same face of the moon from the earth.The moon revolves counterclockwise around the earth along its orbit, which does not overlap the ecliptic plane but is tipped by an angle of 5°9′. Also, the axis of the earth model is rotated by an inclined angle of 23°27′ between the orbital plane and the equatorial plane. As the moon spins on its axis, the axis itself wobbles like a gyroscope and its rotation period is about 18.6 years. Therefore, the moon’s position in the sky is between 28°36′ south and 28°36′ north of the equator (Figure3). We can derive the moon’s position in the earth-based and the sun-based coordinate systems after the earth’s position has been determined.Figure 3
The coordinate systems of the sun, earth, and moon.The 3D model of the sun, earth, and the moon for displaying their relative motion and lunar phases can be developed by the computer simulation (Figure4). We have designed the control program using Shiva3D, which obtains the current time from system API programs to determine the positions and rotation angles of the earth and the moon in the sun-based coordinate system. Then, we rotate the earth model and the moon’s revolution orbit by their inclined angles. Finally, the center of the moon’s revolution orbit is transformed to the earth center such that both their positions are calculated in the sun-based coordinate system. After the new positions of the moon and earth have been obtained, their rotational angles must also be computed before the rendering process takes place. We set up two cameras, one from the outer space and the other at the user’s GPS coordinates on the earth model, to display the motion of earth and the moon as well as the change of lunar phases.Figure 4
The 3D model of the sun, earth, and moon.The completed lunar-phase observation system can be executed on Android mobile devices. Science teachers can download it from Google Play and install on their smart phones or tablet PCs for teaching applications. The system is designed based on the learning units of “Lunar phase observation” and “The sun, earth, and moon” in K12 Science and Life Technology Curriculum [31] for 4th and 9th graders, respectively. The objective of the former is to understand that the lunar phase is periodic by observing the moon in a long-term and regular manner; the objective of the latter is to discover the rising and falling of the moon and the change of lunar phases by the relative motion of the sun, earth, and moon.After starting the system, the user can see the main menu, including the buttons of Observe Lunar Phase, Record Lunar Phase, and Exit (Figure5). The system is designed with five major functions: (1) locating the moon and displaying its lunar phase, (2) setting the system date and time, (3) recording the lunar phase, (4) displaying the moon track, and (5) showing the lunar phase according to the relative position of the sun, earth, and moon. At the beginning, the system obtains the data of current position (from GPS) and date and time (from API). By clicking the button Observe Lunar Phase, the system will activate the electronic compass and 3-axis accelerometer to measure the azimuth and elevation angles of the mobile device.Figure 5
The main menu of the lunar-phase observation system.


## 2.2. Locating the Moon

The system uses a blue arrow to indicate the moon’s direction in the sky (Figure6). As soon as the moon is located, a red circle will appear to surround the moon (Figure 7). After that, the user can click the Record Lunar Phase button to record the lunar phase and its relevant data. The user can also click the Record Data button to check the recorded data. To prevent from pressing the button accidentally, the system can only record the lunar phase when the moon is inside the red circle. Also, it will show the message “Success” or “Failure” to notify the user if the lunar phase is recorded successfully or not.Figure 6
The arrow showing the moon’s direction.Figure 7
Locating the moon inside the red circle.


## 2.3. System Date and Time

The user can change the system date and time by clicking the Set Date and Set Time buttons, and the current time can also be restored by clicking the current time button (Figure8).Figure 8
Change the system date and time.


## 2.4. Recording the Lunar Phase

By clicking the Record Data button on the main menu, the user can record the lunar phase hourly or daily and the system will record the lunar phase and its relative information, including azimuth angle, elevation angle, date, time, and position, accordingly (Figure9). After recording the data, the user may convert them into organized and meaningful information with the functions of displaying the moon track in the sky and showing lunar phases according to relative positions of the sun, earth, and moon to help the user understand the lunar concepts.Figure 9
Recording the lunar phase and its relative information.


## 2.5. Displaying the Moon Track

By clicking the button of Display Moon Track, the system will show the lunar phases by the order of recorded times in one day (Figure10). When clicking the data displayed on top of the screen, the user will see the corresponding lunar phase shown in Figure 10. This function allows the user to see the different positions of the moon in the sky and the variation of its azimuth and elevation angles as time changes.Figure 10
Displaying the moon track in the sky.


## 2.6. Cause of the Lunar Phase

The system has a built-in 3D model to simulate the relative motion of the sun, earth, and moon, which can be used to illustrate the cause of lunar phase (Figure11). By clicking the Start button, the system will apply the recorded data to the 3D model to demonstrate the cause of lunar phases with the perspective view from the outer space. The user can see the relative positions of the three planets and the corresponding lunar phase and its related data.Figure 11
The 3D model to demonstrate the cause of lunar phases.


## 3. Teaching Experiment

In this study, a teaching experiment has been conducted at an elementary school in Taichung, Taiwan, for more than a month to analyze the learning effectiveness of students by using the lunar-phase observation system for learning lunar concepts. Two classes of 4th graders were randomly selected as experimental samples, one as the experimental group (27 students) and the other as the control group (29 students). This study adopted the “nonequivalent groups pretest and posttest” design to analyze whether the system could enhance the students’ learning effectiveness about lunar concepts. In this experiment, the independent variable is teaching method; the covariant is students’ knowledge about lunar concepts before learning; the dependent variable is their knowledge about lunar concepts after learning; the control variables are the teacher, instruction time, and learning contents. A questionnaire survey and interviews with students have been conducted to understand the attitudes of experimental group students after using the system, and the results could also be used as a reference for improving the system. The flowchart of the teaching experiment is shown in Figure12.Figure 12
Flowchart of the teaching experiment.


### 3.1. Research Tools

The research tools used in this study include the lunar-phase observation system, the achievement test of lunar concepts, a questionnaire survey, and interviews on the issue of system acceptance. The questionnaire was designed according to Likert’s [32] five-point scale (strongly agree: 5 points; agree: 4 points; no opinion: 3 points; disagree: 2 points; strongly disagree: 1 point). There are 20 questions divided into 5 parts: basic information, ease of use, usefulness, user’s attitudes, and willingness of using the system. Before the survey, the questions were reviewed and modified by two experts to enhance the correctness. The overall reliability Cronbach’s α = 0.89 > 0.7, indicating the questionnaire, is highly reliable. The interviews were conducted after the experimental group had completed the lunar-phase observation. Six students were purposively selected from this group as interviewees: two with the most progress, two with the least progress, and two with the most observation records. The interviews were mainly about the feedback from students after using the system, and the results were recorded with their approval.


### 3.2. Learning Objectives

The teaching materials were developed according to the learning unit “Lunar phase observation” and the achievement test of lunar concepts was designed based on the textbook, workbook, and teacher’s guide from three textbook publishers in Taiwan. The researchers talked with some science teachers to decide the learning contents as the misconceptions in lunar phases commonly seen from elementary students and the practical issues during moon observation as well as the learning topics covered by the ability indicators as listed below:(i)
understanding the concepts that the moon appears later day by day and it is closer to the east when observed at the same time for the day after,(ii)
understanding the relation between the lunar phase and the lunar calendar,(iii)
knowing the names of lunar phases and their relation with the lunar calendar,(iv)
knowing the sequence of lunar phases and discovering that they occur periodically,(v)
knowing how to observe the lunar phase and record its related data.


### 3.3. Teaching Activity

Before the teaching experiment, the students in both groups took the pretest. Then, they began to observe the moon for one month. The experimental group used the lunar-phase observation system developed in this study (Figure13) and the control group followed the traditional observation method and recorded lunar phases on a worksheet. After the experiment, both groups took the posttest. Their scores were analyzed to see if the lunar-phase observation system could achieve better learning effectiveness than that using the traditional method. A questionnaire survey and interviews were further conducted to investigate the attitudes of students after using the system. The data collected in this experiment includes (1) pretest scores, (2) posttest scores, (3) questionnaire results, and (4) interview results from the experimental group. Finally, the achievement test scores were analyzed by the independent samples t-test, paired samples t-test, and ANCOVA. The questionnaire results were processed by accumulative statistics.Figure 13
Using the lunar-phase observation system to conduct learning.


### 3.4. Learning Effectiveness

To assess students’ prior knowledge about lunar concepts before the teaching experiment, an independent samplest-test is conducted according to their pretest scores. Before that, the assumption of homogeneity of variance has to be met, so the data are analyzed by Levene’s test and the results show that f=1.85 and the significance p=0.18>0.05, indicating no significant difference and thus satisfying the homogeneity of variance. After applying the independent samples t-test to analyze the pretest scores of the two groups, the t value is computed as 0.41 and the significance p=0.69>0.05, which is higher than the standard of significance difference. In other words, the pretest scores for both groups have no significant difference and their abilities in lunar concepts are about the same. This study adopted the paired samples t-test to examine if the experimental group made significant progress in learning lunar concepts. According to the results in Table 1, the average pretest score of experimental group is 40.89 and the average posttest score is 48.44. The t value is computed as −2.72 and the significance p=0.01<0.05, indicating that the experimental group has made significant progress after using the lunar-phase observation system for learning lunar concepts.Table 1
Paired samplest-test results of the experimental group.
Average S. D. Progress t value Significance Pretest 40.89 13.83 7.55 −2.72 0.01 Posttest 48.44 14.09This study also used the paired samplest-test to examine if the control group made significant progress in learning lunar concepts. According to the results in Table 2, the average pretest score of control group is 38.62 and the average posttest is 39.17. The t value is computed as −0.24 and the significance as p=0.81>0.05, indicating that the control group did not make significant progress by using the traditional method for learning the lunar concepts.Table 2
Paired samplest-test results of the control group.
Score Mean S. D. Progress t value Significance Pretest 38.62 16.81 0.55 −0.24 0.81 Posttest 39.17 17.90This study applied a one-way ANCOVA to analyze if the learning effectiveness of these two groups has a significant difference after the experiment. In this analysis, the teaching method is the independent variable, the pretest score is the covariance, and the posttest score is the dependent variable. Before conducting the ANCOVA, it is required to meet the assumption of the homogeneity of variance and within-group regression coefficient. This study used Levene’s test to analyze the homogeneity of variance and the results show that the significancep=0.98>0.05, satisfying the assumption of the homogeneity of variance. As for the homogeneity of within-group regression coefficient, the significance p=0.16 is higher than the significance standard. In other words, there is no significant difference and the ANCOVA can be conducted to see if a significant difference exists in learning effectiveness between these two groups.The ANCOVA results in Table3 show that f=5.32 and p=0.025<0.05. A significant difference exists between the two groups after the experiment. Since the experimental group’s progress is 7.55 and that of the control group is only 0.55, it can be inferred that the experimental group performed better than the control group in learning lunar concepts.Table 3
ANCOVA results of learning effectiveness for the two groups.
Source S. S. D. F. M. S. F Significance Group 834.57 1 834.57 5.32 0.025 Error 8313.44 53 156.86


### 3.5. Questionnaire Results

A questionnaire survey was conducted to analyze the attitudes of students after using the lunar-phase observation system, and the results are summarized in the following (the average score of the 5-point scale is noted byS).


#### 3.5.1. Basic Information

Regarding the frequency of using the system, 60% of the students observed the lunar phase once or twice a day; 25% of the students conducted observation at least five times a day. As for the time spent on observation, most students spent less than 10 minutes per day and 50% of the students spent less than 5 minutes, indicating that the students used the system frequently but without spending too much time in observation.


#### 3.5.2. Ease of Use

Most students agreed that “The user interface is easy to understand” (S=4.6) and “Learning to operate the system is easy” (S=4.6). Only a few students did not know how to use the arrow head as guidance to locate the moon at the beginning. Some other students suggested that it would be more convenient if the system allowed them to connect to the Internet for obtaining information about the lunar phase and submitting their feedback for discussion.


#### 3.5.3. Usefulness

Most students agreed that “The system helps me record lunar phases” (S=4.55) and “The system is useful in finding the information about lunar phases” (S=4.55). Besides, they thought the system is more helpful in distinguishing the first quarter moon from the last quarter moon.


#### 3.5.4. User’s Attitudes

Most students agreed that “I like to use the system to observe the moon” (S=4.6) and “I consider it worthwhile to observe the moon using the system” (S=4.55). Students were impressed by the instant display of the lunar phase, and they considered it useful to observe the moon using the system. Since the system can be used indoors, they thought the observation is not affected by weather conditions.


#### 3.5.5. Willingness of Using the System

Most students agreed that “I will use the system if I have to observe and record lunar phases” (S=4.65) and “I will consider using the system first when needed” (S=4.45). Compared with the traditional observation method, students would like to use the system for learning lunar concepts because in the past they could only obtain knowledge from textbooks and now the observation could be done anytime and anywhere. In addition, they thought the azimuth and elevation angles could be recorded easily without using a compass or an elevation indicator.


#### 3.5.6. Usability Metrics (Observation Days and Completion Rate of the Observation Assignment)

The system can be used to observe and record lunar phases anytime and anywhere and it is not affected by the weather condition or the time when the moon appears. According to the experimental results, the average number of observation days within a month (31 days) for the experimental group is 17.8 days and that of the control group is only 4.6 days. Also, the completion rate of observation assignment for the experimental group (57.4%) is much higher than the completion rate of the control group (14.9%).


### 3.6. Findings in the Experiment

The teaching activities for both groups were conducted in classroom. The teacher demonstrated the skills for observing the moon to the control group first and gave each student a worksheet to record the lunar phases within a month. The experimental group students downloaded and installed the lunar-phase observation system on their tablet PCs before the teaching activity. After that, the teacher demonstrated the major functions of the system and its operating procedure to them. Since the control group used the worksheet for recording the lunar phases, some students were bored when the teacher was explaining the details about how to record the lunar phase on the worksheet. Some students were not familiar with the way of recording the lunar phase and thus made a lot of mistakes. The experimental group students were interested in operating the system and they could not wait to raise tablet PCs to locate the moon before the teacher finished the instruction. Moreover, they were very active in asking questions about the system during the class.To verify the accuracy of students’ observation records, this study consulted Taipei Astronomical Museum for the azimuth and elevation angles of the moon at 8 pm on June 1st, which were 158.5 degrees and 47.5 degrees, respectively. Figure14 shows the lunar phases and their data recorded by Student A in the control group (a) and Student B in the experimental group (b). It can be seen that the azimuth and elevation angles recorded by Student A were both wrong. Moreover, the student could not draw the correct track of the moon in the sky. It is possible that Student A did not use a compass and an elevation indicator to measure the azimuth and elevation angles correctly. Before the bedtime, he could only draw three lunar phases on the worksheet, not enough to show the complete moon track in the sky.Figure 14
The lunar data recorded by Student A and Student B.
(a) (b)The lunar data of Student B were recorded on the system, which show the detailed information about the lunar phase in each hour, including the date and time in the general and lunar calendars as well as the azimuth and elevation angles. In addition, the moon track in the sky is shown clearly, similar to the one recorded by Taipei Astronomical Museum. Therefore, it can explain why students in the experimental group could learn lunar concepts better and easier than the control group. The main reason is keeping correct and complete lunar data to show the moon track in the sky and the cause of lunar phases according to the relative motions of the sun, earth, and moon.To realize how the system could help students collect data about lunar phases, the statistics of observation days by both groups are shown in Table4 and Figure 15, where the average observation days for the experimental group are 17.8 days, with the minimum of 5 days and the maximum of 27 days. Sixteen students in the experimental group observed the lunar phase for at least 16 days, and some of them even conducted observation every day. On the contrary, the average number of observation days for the control group is 4.6 days, with the minimum of 0 days and the maximum of 8 days. Besides, 17 students in the control group observed the lunar phase for less than 6 days, and none of them made the observation for more than 10 days. On average, the control group observed the lunar phase about once a week, and there were 2 students who did not conduct observation at all.Table 4
Statistics of observation days for both groups.
Group Students Minimum Maximum Average Experimental 27 5.0 27.0 17.8 Control 29 0.0 8.0 4.6Figure 15
Statistics of observation days for both groups.A comparison of observation records by the two groups can be found in Table5 and Figure 16. The average number of records for the experimental group is 48.9, with the minimum of 6 records and the maximum of 285 records. There were 12 students in the experimental group with more than 36 records, indicating that the observation records were taken at least once a day. On the other hand, the average number of records for the control group is 5.5, about once per week, with the minimum of 0 records and the maximum of 14 records. Besides, half of the control group students had no more than 5 records, and, what is worse, there were three students without keeping any records at all.Table 5
Statistics of observation days for both groups.
Group Students Minimum Maximum Average Experimental 27 6.0 285.0 48.9 Control 29 0.0 14.0 5.5Figure 16
Statistics of observation records for both groups.To understand how the weather and time affected the two groups in observing the moon, this study checked the timetable of moon rise and daily rainfall data (Table6) provided by the Central Weather Bureau (CWB), Taiwan. Apparently, there was no chance to see the moon from May 19th to 23rd because these days were close to the end of a lunar month. Moreover, it was raining from June 7th to 18th such that the control group could not observe the moon due to early moonrise or bad weather during these days. However, the experimental group could continue observation using the system without being affected by bad weather or the late time of moonrise.Table 6
Statistics of daily moonrise, rainfall, and students conducting observation (2012/05/19 to 2012/06/18).
Date Moonrise Rainfall (mm) Experimental group Control group May 19 03:48 4.9 19 0 May 20 04:27 20.7 16 0 May 21 05:10 — 10 0 May 22 05:56 — 21 0 May 23 06:46 — 19 0 May 24 07:37 — 25 17 May 25 08:30 — 13 4 May 26 09:25 — 10 0 May 27 10:20 1.3 15 0 May 28 11:16 13.6 17 3 May 29 12:13 68.4 25 4 May 30 13:11 — 4 7 May 31 14:12 — 13 10 June 1 15:16 — 18 23 June 2 16:23 — 10 21 June 3 17:30 — 22 5 June 4 18:36 — 20 18 June 5 19:39 — 18 17 June 6 20:35 — 20 5 June 7 21:25 0.1 10 0 June 8 22:09 8.2 12 0 June 9 22:49 20.7 16 0 June 10 23:26 23.2 15 0 June 11 — 38.7 20 0 June 12 00:01 70.1 20 0 June 13 00:36 0.9 9 0 June 14 01:11 33.3 14 0 June 15 01:47 6.2 11 0 June 16 02:26 2.9 14 0 June 17 03:08 4.7 16 0 June 18 03:53 1.1 9 0


## 3.1. Research Tools

The research tools used in this study include the lunar-phase observation system, the achievement test of lunar concepts, a questionnaire survey, and interviews on the issue of system acceptance. The questionnaire was designed according to Likert’s [32] five-point scale (strongly agree: 5 points; agree: 4 points; no opinion: 3 points; disagree: 2 points; strongly disagree: 1 point). There are 20 questions divided into 5 parts: basic information, ease of use, usefulness, user’s attitudes, and willingness of using the system. Before the survey, the questions were reviewed and modified by two experts to enhance the correctness. The overall reliability Cronbach’s α = 0.89 > 0.7, indicating the questionnaire, is highly reliable. The interviews were conducted after the experimental group had completed the lunar-phase observation. Six students were purposively selected from this group as interviewees: two with the most progress, two with the least progress, and two with the most observation records. The interviews were mainly about the feedback from students after using the system, and the results were recorded with their approval.


## 3.2. Learning Objectives

The teaching materials were developed according to the learning unit “Lunar phase observation” and the achievement test of lunar concepts was designed based on the textbook, workbook, and teacher’s guide from three textbook publishers in Taiwan. The researchers talked with some science teachers to decide the learning contents as the misconceptions in lunar phases commonly seen from elementary students and the practical issues during moon observation as well as the learning topics covered by the ability indicators as listed below:(i)
understanding the concepts that the moon appears later day by day and it is closer to the east when observed at the same time for the day after,(ii)
understanding the relation between the lunar phase and the lunar calendar,(iii)
knowing the names of lunar phases and their relation with the lunar calendar,(iv)
knowing the sequence of lunar phases and discovering that they occur periodically,(v)
knowing how to observe the lunar phase and record its related data.


## 3.3. Teaching Activity

Before the teaching experiment, the students in both groups took the pretest. Then, they began to observe the moon for one month. The experimental group used the lunar-phase observation system developed in this study (Figure13) and the control group followed the traditional observation method and recorded lunar phases on a worksheet. After the experiment, both groups took the posttest. Their scores were analyzed to see if the lunar-phase observation system could achieve better learning effectiveness than that using the traditional method. A questionnaire survey and interviews were further conducted to investigate the attitudes of students after using the system. The data collected in this experiment includes (1) pretest scores, (2) posttest scores, (3) questionnaire results, and (4) interview results from the experimental group. Finally, the achievement test scores were analyzed by the independent samples t-test, paired samples t-test, and ANCOVA. The questionnaire results were processed by accumulative statistics.Figure 13
Using the lunar-phase observation system to conduct learning.


## 3.4. Learning Effectiveness

To assess students’ prior knowledge about lunar concepts before the teaching experiment, an independent samplest-test is conducted according to their pretest scores. Before that, the assumption of homogeneity of variance has to be met, so the data are analyzed by Levene’s test and the results show that f=1.85 and the significance p=0.18>0.05, indicating no significant difference and thus satisfying the homogeneity of variance. After applying the independent samples t-test to analyze the pretest scores of the two groups, the t value is computed as 0.41 and the significance p=0.69>0.05, which is higher than the standard of significance difference. In other words, the pretest scores for both groups have no significant difference and their abilities in lunar concepts are about the same. This study adopted the paired samples t-test to examine if the experimental group made significant progress in learning lunar concepts. According to the results in Table 1, the average pretest score of experimental group is 40.89 and the average posttest score is 48.44. The t value is computed as −2.72 and the significance p=0.01<0.05, indicating that the experimental group has made significant progress after using the lunar-phase observation system for learning lunar concepts.Table 1
Paired samplest-test results of the experimental group.
Average S. D. Progress t value Significance Pretest 40.89 13.83 7.55 −2.72 0.01 Posttest 48.44 14.09This study also used the paired samplest-test to examine if the control group made significant progress in learning lunar concepts. According to the results in Table 2, the average pretest score of control group is 38.62 and the average posttest is 39.17. The t value is computed as −0.24 and the significance as p=0.81>0.05, indicating that the control group did not make significant progress by using the traditional method for learning the lunar concepts.Table 2
Paired samplest-test results of the control group.
Score Mean S. D. Progress t value Significance Pretest 38.62 16.81 0.55 −0.24 0.81 Posttest 39.17 17.90This study applied a one-way ANCOVA to analyze if the learning effectiveness of these two groups has a significant difference after the experiment. In this analysis, the teaching method is the independent variable, the pretest score is the covariance, and the posttest score is the dependent variable. Before conducting the ANCOVA, it is required to meet the assumption of the homogeneity of variance and within-group regression coefficient. This study used Levene’s test to analyze the homogeneity of variance and the results show that the significancep=0.98>0.05, satisfying the assumption of the homogeneity of variance. As for the homogeneity of within-group regression coefficient, the significance p=0.16 is higher than the significance standard. In other words, there is no significant difference and the ANCOVA can be conducted to see if a significant difference exists in learning effectiveness between these two groups.The ANCOVA results in Table3 show that f=5.32 and p=0.025<0.05. A significant difference exists between the two groups after the experiment. Since the experimental group’s progress is 7.55 and that of the control group is only 0.55, it can be inferred that the experimental group performed better than the control group in learning lunar concepts.Table 3
ANCOVA results of learning effectiveness for the two groups.
Source S. S. D. F. M. S. F Significance Group 834.57 1 834.57 5.32 0.025 Error 8313.44 53 156.86


## 3.5. Questionnaire Results

A questionnaire survey was conducted to analyze the attitudes of students after using the lunar-phase observation system, and the results are summarized in the following (the average score of the 5-point scale is noted byS).


### 3.5.1. Basic Information

Regarding the frequency of using the system, 60% of the students observed the lunar phase once or twice a day; 25% of the students conducted observation at least five times a day. As for the time spent on observation, most students spent less than 10 minutes per day and 50% of the students spent less than 5 minutes, indicating that the students used the system frequently but without spending too much time in observation.


### 3.5.2. Ease of Use

Most students agreed that “The user interface is easy to understand” (S=4.6) and “Learning to operate the system is easy” (S=4.6). Only a few students did not know how to use the arrow head as guidance to locate the moon at the beginning. Some other students suggested that it would be more convenient if the system allowed them to connect to the Internet for obtaining information about the lunar phase and submitting their feedback for discussion.


### 3.5.3. Usefulness

Most students agreed that “The system helps me record lunar phases” (S=4.55) and “The system is useful in finding the information about lunar phases” (S=4.55). Besides, they thought the system is more helpful in distinguishing the first quarter moon from the last quarter moon.


### 3.5.4. User’s Attitudes

Most students agreed that “I like to use the system to observe the moon” (S=4.6) and “I consider it worthwhile to observe the moon using the system” (S=4.55). Students were impressed by the instant display of the lunar phase, and they considered it useful to observe the moon using the system. Since the system can be used indoors, they thought the observation is not affected by weather conditions.


### 3.5.5. Willingness of Using the System

Most students agreed that “I will use the system if I have to observe and record lunar phases” (S=4.65) and “I will consider using the system first when needed” (S=4.45). Compared with the traditional observation method, students would like to use the system for learning lunar concepts because in the past they could only obtain knowledge from textbooks and now the observation could be done anytime and anywhere. In addition, they thought the azimuth and elevation angles could be recorded easily without using a compass or an elevation indicator.


### 3.5.6. Usability Metrics (Observation Days and Completion Rate of the Observation Assignment)

The system can be used to observe and record lunar phases anytime and anywhere and it is not affected by the weather condition or the time when the moon appears. According to the experimental results, the average number of observation days within a month (31 days) for the experimental group is 17.8 days and that of the control group is only 4.6 days. Also, the completion rate of observation assignment for the experimental group (57.4%) is much higher than the completion rate of the control group (14.9%).


## 3.5.1. Basic Information

Regarding the frequency of using the system, 60% of the students observed the lunar phase once or twice a day; 25% of the students conducted observation at least five times a day. As for the time spent on observation, most students spent less than 10 minutes per day and 50% of the students spent less than 5 minutes, indicating that the students used the system frequently but without spending too much time in observation.


## 3.5.2. Ease of Use

Most students agreed that “The user interface is easy to understand” (S=4.6) and “Learning to operate the system is easy” (S=4.6). Only a few students did not know how to use the arrow head as guidance to locate the moon at the beginning. Some other students suggested that it would be more convenient if the system allowed them to connect to the Internet for obtaining information about the lunar phase and submitting their feedback for discussion.


## 3.5.3. Usefulness

Most students agreed that “The system helps me record lunar phases” (S=4.55) and “The system is useful in finding the information about lunar phases” (S=4.55). Besides, they thought the system is more helpful in distinguishing the first quarter moon from the last quarter moon.


## 3.5.4. User’s Attitudes

Most students agreed that “I like to use the system to observe the moon” (S=4.6) and “I consider it worthwhile to observe the moon using the system” (S=4.55). Students were impressed by the instant display of the lunar phase, and they considered it useful to observe the moon using the system. Since the system can be used indoors, they thought the observation is not affected by weather conditions.


## 3.5.5. Willingness of Using the System

Most students agreed that “I will use the system if I have to observe and record lunar phases” (S=4.65) and “I will consider using the system first when needed” (S=4.45). Compared with the traditional observation method, students would like to use the system for learning lunar concepts because in the past they could only obtain knowledge from textbooks and now the observation could be done anytime and anywhere. In addition, they thought the azimuth and elevation angles could be recorded easily without using a compass or an elevation indicator.


## 3.5.6. Usability Metrics (Observation Days and Completion Rate of the Observation Assignment)

The system can be used to observe and record lunar phases anytime and anywhere and it is not affected by the weather condition or the time when the moon appears. According to the experimental results, the average number of observation days within a month (31 days) for the experimental group is 17.8 days and that of the control group is only 4.6 days. Also, the completion rate of observation assignment for the experimental group (57.4%) is much higher than the completion rate of the control group (14.9%).


## 3.6. Findings in the Experiment

The teaching activities for both groups were conducted in classroom. The teacher demonstrated the skills for observing the moon to the control group first and gave each student a worksheet to record the lunar phases within a month. The experimental group students downloaded and installed the lunar-phase observation system on their tablet PCs before the teaching activity. After that, the teacher demonstrated the major functions of the system and its operating procedure to them. Since the control group used the worksheet for recording the lunar phases, some students were bored when the teacher was explaining the details about how to record the lunar phase on the worksheet. Some students were not familiar with the way of recording the lunar phase and thus made a lot of mistakes. The experimental group students were interested in operating the system and they could not wait to raise tablet PCs to locate the moon before the teacher finished the instruction. Moreover, they were very active in asking questions about the system during the class.To verify the accuracy of students’ observation records, this study consulted Taipei Astronomical Museum for the azimuth and elevation angles of the moon at 8 pm on June 1st, which were 158.5 degrees and 47.5 degrees, respectively. Figure14 shows the lunar phases and their data recorded by Student A in the control group (a) and Student B in the experimental group (b). It can be seen that the azimuth and elevation angles recorded by Student A were both wrong. Moreover, the student could not draw the correct track of the moon in the sky. It is possible that Student A did not use a compass and an elevation indicator to measure the azimuth and elevation angles correctly. Before the bedtime, he could only draw three lunar phases on the worksheet, not enough to show the complete moon track in the sky.Figure 14
The lunar data recorded by Student A and Student B.
(a) (b)The lunar data of Student B were recorded on the system, which show the detailed information about the lunar phase in each hour, including the date and time in the general and lunar calendars as well as the azimuth and elevation angles. In addition, the moon track in the sky is shown clearly, similar to the one recorded by Taipei Astronomical Museum. Therefore, it can explain why students in the experimental group could learn lunar concepts better and easier than the control group. The main reason is keeping correct and complete lunar data to show the moon track in the sky and the cause of lunar phases according to the relative motions of the sun, earth, and moon.To realize how the system could help students collect data about lunar phases, the statistics of observation days by both groups are shown in Table4 and Figure 15, where the average observation days for the experimental group are 17.8 days, with the minimum of 5 days and the maximum of 27 days. Sixteen students in the experimental group observed the lunar phase for at least 16 days, and some of them even conducted observation every day. On the contrary, the average number of observation days for the control group is 4.6 days, with the minimum of 0 days and the maximum of 8 days. Besides, 17 students in the control group observed the lunar phase for less than 6 days, and none of them made the observation for more than 10 days. On average, the control group observed the lunar phase about once a week, and there were 2 students who did not conduct observation at all.Table 4
Statistics of observation days for both groups.
Group Students Minimum Maximum Average Experimental 27 5.0 27.0 17.8 Control 29 0.0 8.0 4.6Figure 15
Statistics of observation days for both groups.A comparison of observation records by the two groups can be found in Table5 and Figure 16. The average number of records for the experimental group is 48.9, with the minimum of 6 records and the maximum of 285 records. There were 12 students in the experimental group with more than 36 records, indicating that the observation records were taken at least once a day. On the other hand, the average number of records for the control group is 5.5, about once per week, with the minimum of 0 records and the maximum of 14 records. Besides, half of the control group students had no more than 5 records, and, what is worse, there were three students without keeping any records at all.Table 5
Statistics of observation days for both groups.
Group Students Minimum Maximum Average Experimental 27 6.0 285.0 48.9 Control 29 0.0 14.0 5.5Figure 16
Statistics of observation records for both groups.To understand how the weather and time affected the two groups in observing the moon, this study checked the timetable of moon rise and daily rainfall data (Table6) provided by the Central Weather Bureau (CWB), Taiwan. Apparently, there was no chance to see the moon from May 19th to 23rd because these days were close to the end of a lunar month. Moreover, it was raining from June 7th to 18th such that the control group could not observe the moon due to early moonrise or bad weather during these days. However, the experimental group could continue observation using the system without being affected by bad weather or the late time of moonrise.Table 6
Statistics of daily moonrise, rainfall, and students conducting observation (2012/05/19 to 2012/06/18).
Date Moonrise Rainfall (mm) Experimental group Control group May 19 03:48 4.9 19 0 May 20 04:27 20.7 16 0 May 21 05:10 — 10 0 May 22 05:56 — 21 0 May 23 06:46 — 19 0 May 24 07:37 — 25 17 May 25 08:30 — 13 4 May 26 09:25 — 10 0 May 27 10:20 1.3 15 0 May 28 11:16 13.6 17 3 May 29 12:13 68.4 25 4 May 30 13:11 — 4 7 May 31 14:12 — 13 10 June 1 15:16 — 18 23 June 2 16:23 — 10 21 June 3 17:30 — 22 5 June 4 18:36 — 20 18 June 5 19:39 — 18 17 June 6 20:35 — 20 5 June 7 21:25 0.1 10 0 June 8 22:09 8.2 12 0 June 9 22:49 20.7 16 0 June 10 23:26 23.2 15 0 June 11 — 38.7 20 0 June 12 00:01 70.1 20 0 June 13 00:36 0.9 9 0 June 14 01:11 33.3 14 0 June 15 01:47 6.2 11 0 June 16 02:26 2.9 14 0 June 17 03:08 4.7 16 0 June 18 03:53 1.1 9 0


## 4. Conclusions

In this study, a lunar-phase observation system is developed using the AR technology and sensor functions on mobile devices to help elementary and high school students observe and record lunar phases. The system allows them to observe lunar phases in real situations by holding the mobile device towards the moon’s direction, and the screen will show the virtual moon overlapping the real moon. The system has a built-in 3D model to simulate the relative motion of the sun, earth, and moon, and it can convert the recorded data into the moon track in the sky to establish connection between the lunar phase and the relative positions of the sun, earth, and moon. Therefore, it can help students develop correct lunar concepts, especially for those lacking spatial concepts. Also, the physical operation during observation makes a deeper impression on students so as to store the obtained knowledge in the long-term memory. In addition, the system can shorten the learning process by setting different dates and times for observation, and it can solve the problem of being unable to observe lunar phases due to bad weather or obstruction by tall buildings. Therefore, it is an effective tool for astronomy education in elementary and high schools.A teaching experiment was conducted to analyze the learning effectiveness of students using the lunar-phase observation system for learning lunar concepts. A questionnaire survey was also conducted to understand the attitudes of students after the teaching experiment. The results of achievement test show that the learning effectiveness of the experimental group is significantly higher than that of the control group. The questionnaire survey and interview results reveal that most students preferred to use the system for observing the lunar phase. They considered the system useful in terms of locating the moon and recording the lunar data. In addition, most students agreed that the system is easy to operate, and they would like to use it again if they have a similar requirement in the future. Finally, the future works for this study are listed in the following based on the experimental results and research findings.(i)
The system was developed with Shiva3D, which does not support Chinese input. Thus, it is expected that the version with the library of Chinese language or plug-in for Android to support Chinese input will be released soon such that the researchers can develop the functions for students to write down their feedback about lunar-phase observation in Chinese with their classmates.(ii)
The functions to support online search and upload recorded data via wireless networks will be added to the system such that the teachers are able to know the learning progress of students and know if they have encountered any problems in learning lunar concepts.(iii)
In addition to the lunar-phase observation, stars are also important celestial bodies for astronomical observation in the K12 science and technology curriculums. Therefore, this study intends to include the functions of star observation in the future to make the system a more useful tool for astronomy education.



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*Source: 8352791-2016-05-30.xml*