Every clock, calendar, and time zone we use today is rooted in the sky. Long before mechanical clocks or GPS, people watched the rising and setting of the Sun, the phases of the Moon, and the shifting stars to keep track of time and navigate the world.
During this lesson, we’ll uncover how the motions of celestial objects define our days, months, and years—and how modern astronomers still rely on these ancient rhythms. As you read, think about this: What can the sky tell us about where we are, and when we are?
Watch the Science Lesson
VIDEO COMING SOON! (After Live Class is completed.)
Do the Assignments
Homework
Each week, you'll be assigned a set of discussion questions, quantitative problems, and quiz questions. Begin with the discussion questions to make sure you're understanding the material presented in class. Then move into the homework problems, skipping any that are challenging or you’re not sure how to start (saving them for after you’ve worked on other problems first.) Continue working on these problems each day until you’ve completed the set.
Space Podcast
Each week, students choose a space-related podcast episode to listen to and write a short summary in their journal. These reflections help students stay connected to current science news while developing their ability to explain scientific concepts in their own words. (Suggested podcasts are in the Astronomy Info Packet.)
Lab Project Activity
Below you'll find several short videos about telling time using the stars, and even create a scientific instrument to measure the location of stars! Download your lab project, and use the step-by-step instructional videos to walk you through every part of the assignment.
- Theodolite: A theodolite is a surveying instrument used to measure horizontal and vertical angles. In astronomy, it can be used to measure the altitude and azimuth of celestial objects. (3D print one here.)
- Right Ascension (RA) and Declination (Dec): These are celestial coordinates used to locate objects in the night sky. RA is like longitude and Dec is like latitude.
Discovery Project (Optional)
Astronomy is built on a foundation of key observations—not just of objects, but of celestial events and phenomena. The great astronomers of the past didn’t simply observe the sky; they measured, recorded, and carefully analyzed what they saw. Our modern understanding of the universe rests on the work they left behind. The remarkable part is that we can still replicate many of their foundational observations ourselves. These projects take effort and often involve math, but they’re worth it.
Why? Because truly learning a subject means more than just memorizing facts—it means understanding how those facts were discovered and why they matter. Just as biology students dissect frogs and chemistry students run experiments, astronomy students must engage with the sky directly. It's through doing that real understanding begins.
Nightly Motion of the Stars
We're going to create time-lapse videos that show the nightly motion of the stars using simple tools to better understand how the celestial sphere works.
Materials:
- Compass (magnetic)
- Protractor
- Clock or stopwatch
- Digital camera (newer cell phones with good cameras can work) with remote release
- Tripod with camera mount adapter
Procedure:
- Download your Discovery Project and find a clear night with little or no moon. (Check moon phase calendar here.)
- Set up your camera so it faces East.
- Make your observations by taking a series of 350-500 images, one per minute.
- Use the directions to do your data reduction to merge the images into a single time-lapse video.
- What motion do you observe? Follow the instructions for graphing this motion.
- Repeat steps 3-6, facing the camera North (instead of East) on the following clear night. (The nights do not need to be consecutive.)