Learning Objectives
- Build reproducible naked-eye observing habits and calibrate hand-angle estimates.
- Make measurements or classifications with explicit uncertainty.
- Separate direct evidence from model-dependent interpretation.
Preparation
- Read OpenStax Astronomy 2e section 2.1 on the sky above and angular measure.
- Bring a notebook or digital observing log, pencil, red-light-safe illumination if observing at night, and weather-appropriate clothing.
Materials and Data
- Naked-eye observing site or simulated sky if weather prevents outdoor work
- Printed or digital horizon diagram
- Optional: Stellarium for post-observation verification
Apparatus and Setup
- Prepare a horizon sheet with a 0-90 degree altitude scale and cardinal direction labels.
- Use a compass or landmark map to establish north before observations begin.
- If using a simulated sky, set location, date, and time before students enter measurements.
Procedure
- Record date, clock time, time zone, observing location, approximate latitude/longitude if known, weather, transparency, and horizon obstructions.
- Identify north, east, south, and west using landmarks, compass, phone compass, or instructor-provided site orientation. Note the method used.
- Calibrate your hand at arm's length: estimate the width of one finger, three fingers, fist, and thumb-to-little-finger span using the class reference values, then record your personal values.
- Choose three bright objects. Estimate each object's altitude and azimuth using hand angles and cardinal directions.
- Wait at least 20 minutes or use two observations separated by class time. Re-estimate one object's position and describe the apparent motion.
- Sketch a horizon diagram with at least three objects, cardinal directions, altitude estimates, and obstructions.
Measurement Record
Use this structure or an equivalent table in your lab notebook.
| object | time | azimuth estimate | altitude estimate | uncertainty | identification method |
|---|---|---|---|---|---|
Analysis and Uncertainty
- Compute the difference between two altitude estimates for the repeated object.
- Estimate uncertainty for each hand-angle measurement, using at least +/- one finger width unless your repeated measurements justify a different value.
- State which details would allow another observer to reproduce your observation.
Deliverables
- One complete observing log entry
- One labeled horizon diagram
- A 150-250 word reflection distinguishing direct observation from interpretation
Assessment Criteria
- Completeness of observing metadata
- Reasonable angular estimates with uncertainty
- Clear labeled diagram
- Correct distinction between observation and model
References, Software, and Data Provenance
- OpenStax Astronomy 2e, section 2.1
- Stellarium: https://stellarium.org/ or https://stellarium-web.org/ for optional verification
Any additional dataset, image, or software source used by an instructor should be added to ../reference-log.md with source, access date, license or usage note, and processing steps.