Measuring Parallax Distance

Use a simple, home-built angle measurer and a known baseline to measure the parallax angle of a nearby target against a distant reference, then calculate the target’s distance with basic trigonometry. The activity demonstrates how stellar parallax works using everyday objects and spaces.

• Refer to links below for methods to measure distances using parallax.

Parallax Lab Tutorial - Dave's Astrotracks:

Parallax Experiment Demonstration Video - Jennifer DeBenedictis:

📄 Parallax in the Lab - Roberto H. Méndez: https://home.ifa.hawaii.edu/users/mendez/ASTRO110LAB11/parallax.html

• Use multiple baselines (e.g., 0.3 m, 0.6 m, 1.0 m) and plot parallax angle versus baseline to see the linear trend.
• Try targets at different distances and compare the resulting parallax angles for a fixed baseline.
• Perform the activity outdoors with very distant references (mountain peak, tall tower) to simulate stellar parallax more closely.

• None available.

• Why must the reference object be much farther away than the target? (A very distant reference minimizes its own apparent shift so the measured change reflects the target’s motion.)
• What happens to the parallax angle if you double the baseline while keeping the target fixed? (It approximately doubles, improving measurement precision.)
• How does measurement uncertainty change with target distance for a fixed baseline? (Parallax angle shrinks as distance increases, making percentage error larger unless baseline increases.)
• How can you reduce percent error in this lab? (Increase baseline, ensure precise alignment, use a very distant reference, repeat and average angles, and verify calculator angle units.)