A Structured Observing Project with Sunset Positions and Moon Phases: Instructor Guide
Authors
Jennifer Scott, Towson University, jescott@towson.edu
Instructor guide, Student instructions, Project questions
Craig Snydal ctsnydal@gmail.com
Scoring script
Summary
This guide describes a novel project structure for sky observations commonly assigned in introductory level astronomy students at either the high school or undergraduate level. The project is an outside class assignment optimized for a large course that meets during the day. The goal of this activity is for students to make independent observations at a fixed time of day to develop an understanding of: (1) how annual motion of the Earth relates to observed position of the Sun as it sets towards the West; and (2) changes in the Moon phase over the lunar month and how the phase of the Moon relates to its position in the sky relative to the Sun. Students synthesize their understanding by responding to summary questions at the conclusion of the project. The questions require students to use their collection of observations to make predictions about future sunset and Moon positions and Moon phases.
A critical component of this work is an associated scoring script, available through GitHub. The algorithm uses Sun and Moon position data and Moon phase data downloaded by the user from the United States Naval Observatory to score student input and provide feedback in an efficient manner. This allows instructors to assign and grade student observations even in a large university class.
1. Learning Objectives
This sky observing project addresses typical learning goals for physical science courses by requiring students to use observations of the real world to construct or build upon their conceptual model of basic concepts in astronomy: motions of the Earth, Moon, and Sun.
Specific project connections to learning goals articulated for core physical science courses at the author’s home institution, Towson University, include:
- Demonstrating knowledge of methods used to collect, interpret, and apply scientific data. Students gather data and must interpret the data by responding to summary questions.
- Articulating relevant basic assumptions, concepts, theoretical constructs and factual information of a discipline. Students use their data to interpret models of the Earth-Moon-Sun system.
- Understanding and applying relevant discipline-specific methodologies and strategies of inquiry. Students gather data with “naked eye” observations, as humans have done throughout recorded history.
2. Description
All observations are made with the naked eye and most measurements are done by hand. Students are encouraged but not required to make all observations from the same location throughout the project.
This project is designed with accessibility in mind. The assignment is not an extra credit option. Instead, all students are required to observe the sky and physical phenomena associated with course material. The specific delivery and scoring of the project through the Learning Management System (LMS, e.g. Blackboard or Canvas) questions and scoring script allow instructors to assess student learning in an efficient manner.
Students are informed of safety issues in the project instructions. They are warned not to look at the sun directly. They are encouraged to consider their personal safety when making outside observations and to work in pairs when possible.
A. Sunset
From their observing location, students find a landmark that lies due West. For this, they may use a map, compass, GPS device, or compass application. All other measurements are done by hand.
For each observation, students measure the angular distance between their due west landmark and the sunset position using their fist width (~10 degrees) or finger widths (1 little finger ~ 1 degree, 3 fingers ~ 5 degrees) held at arm’s length. This angular distance is the value reported.
Students will notice over the project period that the position of the sunset shifts from north to south in the fall months and from south to north in winter-spring. It will set due West on the equinoxes.
B. Moon
At the same time the student makes the sunset observation, they look for the Moon in the sky. If it is visible, they record its phase and its position in the sky.
Students will notice over the project period that (a) there are some dates on which they do not see the Moon and (b) when the Moon is visible, its position in the sky at this fixed time when the Sun is near the western horizon, is related to its phase.
3. Structure
A. Observation timing and cadence
Observations must be made in a reasonable amount of time before sunset, late enough that the sunset position may be accurately estimated but early enough that the sun has not sunk below the observer’s visible horizon. A requirement of 10-45 minutes before local sunset time is reasonable. Students may find local sunset time on any given day with a simple web search. (It may be helpful to remind them about changes when clocks are set forward or backward due to Daylight Savings Time.)
To see appreciable changes over time, the observations must be separated by approximately one week. To allow for flexibility in evening schedules, it is suggested that students be allowed to make each observation within a two-week time period. In an introductory college level course that meets over a 14-week semester, this allows for seven observations that can be summarized and synthesized at the end of the semester.
Students should be given feedback on each observation indicating the true sunset position at the time of their observation. This allows students to recognize errors and make corrections over time.
B. Tolerances
Student observation data is scored using reference data from the United States Naval Observatory. Because students will not make measurements that agree with the USNO positions and Moon phases with 100% accuracy, it is recommended that some tolerances be built into the scoring rubric. Below, we describe some of those tolerances already built into the scoring script. These can be modified by individual users as desired.
For the sunset position, we allow full credit for any result that is less than 90 for the first and second observations. This allows students to read feedback which includes the correct sunset positions to adjust their observing procedure and make more accurate position estimates.
Some students may not initially understand that they are not reporting the reading from a smartphone compass application for example, which gives azimuth angle. Any number greater than 90 is a flag for specific feedback on this point.
Observation number three and beyond must be accurate to within 10 degrees for full credit, although this setting can be adjusted within the script if desired. Students are still given specific feedback on the sunset position to continuously improve their measurement technique.
Moon phase is defined and scored against student input using the fraction illuminated reported by USNO. We allow a tolerance of 10% on this fraction in scoring student responses.
Moon position is defined and scored against student input using the Moon altitude reported by USNO, specifically using the Moon’s altitude at the time of observation relative to its maximum altitude for the day. Students choose from five options for the Moon position in the sky. To avoid position estimates being sensitive at the boundaries between options, a tolerance of 10% is employed to avoid penalty. A tolerance for a Moon that is extremely low on the horizon (altitude below 10 degrees) and/or early crescent phase is also employed.
4. Delivery
Detailed student instructions are linked from the LMS and questions are delivered via the LMS on the desired timescale. We set up a bi-weekly observation form.
A. Observation Questions1
For ease of scoring, questions are constructed as follows:
1. How did you determine the direction of due west? (1st observation for weeks 1-3 only, 1 point)
(a) Compass
(b) GPS, smart phone, or other handheld device
(c) Map
(d) Other
2. If you selected “Other” for #1, explain what method you used. If you did not choose “Other”, leave this blank.
3. What is the address or other specific description of your observation location? It is advisable to use the same location for all observations. (1st observation for weeks 1-3 only, 1 point)
4. Enter the month of your observation date (1-12) as a SINGLE NUMBER within the ranges noted. (4 & 5 together worth 1 point).
Example: Enter the month and day of an observation on Feb. 10 by entering “2” (with no quotes) then “10” NOT by entering “February 10, 2011” or similar text input.
5. Enter the day (1-31) of your observation date as a SINGLE NUMBER within the ranges noted. (4 & 5 together worth 1 point).
6. Enter the hour of your observation time (1-12), as a SINGLE NUMBER within the ranges noted (any ranges entered into Bb itself will result in the first number of that range being used in grading). (6 & 7 together worth 1 point).
Example: Enter the hour and minute of an observation at 5:20 PM by entering “5” (with no quotes) then “20” NOT by entering “5:20 PM” or similar text input.
7. Enter the minute (0-59) of your observation time, as a SINGLE NUMBER within the ranges noted (any ranges entered into Bb itself will result in the first number of that range being used in grading). (6 & 7 together worth 1 point).
8. True or false: The Sun set N of due W. (1 point)
9. Enter number of degrees N or S of due W the sun set. (1 point)
10. True or false: The Moon was visible in the sky at the time I made my observation (yes or no)? (1 point)
WARNING
If you did not see the Moon at sunset, DO NOT say that you did! You may be docked 20 points on your final observing project grade for fabricating an observation. See the instruction web page.
11. Upload your image of the Moon here only if you observed the Moon at sunset on the date you have entered for this observation. If you did not see the Moon, leave this empty and enter 8 for question 12 and “no moon” for questions 13 and 14.
12. View the Moon phases in this image:
Choose the phase, labeled 1-7, that best corresponds to the moon phase you OBSERVED. (2 points) If you saw no moon, choose 8.
13. Which of the following labels matches the phase you entered in the last question? (1 point)
(a) full
(b) waning gibbous
(c) 3rd quarter
(d) waning crescent
(e) waxing crescent
(f) 1st quarter
(g) waxing gibbous
(h) no moon
14. Which of the following positions in the sky best describes your observation of the Moon? (1 point)
(a) close to the eastern horizon
(b) in the eastern sky, between the horizon and overhead (the meridian)
(c) overhead (on the meridian), or close to overhead (the meridian)
(d) in the western sky, between the horizon and overhead (the meridian)
(e) close to the western horizon
(f) no moon
- Fabrication
To discourage students simply looking up information online, they are asked in question #11 to snap a photograph of the Moon if they are reporting they observed it. The photograph is uploaded to the LMS and only checked if there is any discrepancy flagged by the scoring software.
B. Synthesis: Summary Questions1
Summary questions are assigned at end of the full project period. Students demonstrate mastery of concepts.
1. Over the course of the semester the position of the sunset … (2 points)
(a) did not change.
(b) started South of due West and gradually moved North.
(c) started North of due West and gradually moved South.
(d) completed part of its 360 degree path around the horizon.
(e) Both b) and d).
(f) Both c) and d).
2. True or false: The sunset position crossed the position of due West at some point during the semester. (2 points)
3. If the event in the previous question occurred it did so on … (Choose all that apply. 2 points)
(a) The event did not occur.
(b) around September 22
(c) around March 20
(d) around June 21
(e) around December 21
(f) the summer solstice
(g) the vernal equinox
(h) the autumnal equinox
(i) the winter solstice
4. Enter the month of your last observation (1-12). (1 point)
5. Enter the date of your last observation (1-31). (1 point)
6. True or false: In 6 months from your last observation, the sunset will be North of due West. (2 points)
7. Enter the number of degrees the sunset position will be in 6 months in the direction you gave for the previous question. (2 points)
8. True or false: In one year from your last observation, the sunset will be North of due West. (2 points)
9. Enter the number of degrees the sunset position will be in one year in the direction you gave for the previous question. (2 points)
10. What will the Moon’s phase be in two weeks from your last observation? (2 points)
(a) new
(b) waxing crescent
(c) 1st quarter
(d) waxing gibbous
(e) full
(f) waning gibbous
(g) 3rd quarter
(h) waning crescent
11. What will the Moon-Sun angular distance (or separation) in the sky be two weeks from your last observation? (2 points)
(a) about 0 degrees
(b) between 0 and 90 degrees
(c) about 90 degrees
(d) between 90 and 180 degrees
(e) about 180 degrees
12. What will the Moon’s phase be in one month from your last observation? (2 points)
(a) new
(b) waxing crescent
(c) 1st quarter
(d) waxing gibbous
(e) full
(f) waning gibbous
(g) 3rd quarter
(h) waning crescent
13. What will the Moon-Sun angular distance (or separation) in the sky be one month from your last observation? (2 points)
(a) about 0 degrees
(b) between 0 and 90 degrees
(c) about 90 degrees
(d) between 90 and 180 degrees
(e) about 180 degrees
14. Choose one of your observation dates you did NOT see the Moon . Give the month here (1-12) *. (1 point)
*This should be a date you did not see the Moon because it was not up. If there was an observation for which you did not log a Moon observation, but you lost points because it was up in the sky at sunset, do not choose this date here. If you saw the Moon in all your sunset observations, choose one date over the semester the Moon would not have been visible at sunset.
15. Give the day of the month for the date you chose in the previous question (1-31). (1 point)
16. What was the Moon’s phase on the date you entered above? (2 points)
(a) new
(b) waxing crescent
(c) 1st quarter
(d) waxing gibbous
(e) full
(f) waning gibbous
(g) 3rd quarter
(h) waning crescent
17. What was the Moon-Sun angular distance (or separation) on the date you entered above? (2 points)
(a) about 0 degrees
(b) between 0 and 90 degrees
(c) about 90 degrees
(d) between 90 and 180 degrees
(e) about 180 degrees
18. What Moon phases are never visible at sunset? (Choose all that apply, 2 points)
(a) new
(b) waxing crescent
(c) 1st quarter
(d) waxing gibbous
(e) full
(f) waning gibbous
(g) 3rd quarter
(h) waning crescent
(i) None. All phases are in principle visible at sunset.
19. Explain your answer(s) to the previous question. (3 points)
5. Scoring Code
We have developed open-source python scripts available via GitHub for scoring weekly observations that are constructed using the sample question forms above in sections 4.A and 4.C and employing the requirements for cadence and timing discussed in section 3.A and with the scoring tolerances noted in section 3.B.
The observation code requires USNO data tables of Sun positions and Moon phases and positions. These data may be downloaded via GitHub with the script. However, users outside the Baltimore-DC area will need to obtain their own data tables from the USNO Data Services site.22
A. Scoring Individual Observations
The observation scoring code generates student feedback and scores in both plain text files and Excel spreadsheets, allowing for efficient delivery back to the students. The spreadsheet can be used to upload scores and feedback text directly to the student grade application in the LMS.
The observation scoring code also generates flags for instructor follow up on specific student responses, e.g. students who enter observation information outside the dates of the observation period, outside the allowed time window, or who report a questionable Moon observation.
B. Scoring Project Summary
A separate script is provided for scoring the student responses to the summary questions. Except for #19 above, or any additional short responses questions the instructor may wish to include, all summary questions may be scored automatically by retaining student responses from the entire semester.
Details on using the scoring code are included in the README file in the GitHub repository.
1- Upon request, these questions are available as Blackboard Test Export Files.
2- https://www.usno.navy.mil/USNO/astronomical-applications/data-services/data-services Note that the website is temporarily unavailable as of the writing of this guide. A possible alternative source for these data is https://astro.ukho.gov.uk/surfbin/first_beta.cgi
This work is licensed under a Creative Commons Attribution 4.0 International License.