Astronomy

Parallax Lab

Objective: To demonstrate a means to measure distances to objects outside earth’s atmosphere.

Directions:

To determine distance using parallax, you must collect specific data. Use the diagram below to help guide you in collecting the correct data.

A = Angle measured with protractor to object from left side of baseline

B = Angle measured with protractor to object from right side of baseline

S = Baseline measured in meters

C = Parallax Angle

D = Distance to object from baseline

  1. The baseline = ______m
  2. Measured distance to object = ______m
  3. Angle A = ______degrees
  4. Angle B = ______degrees
  5. Parallax angle C = ______degrees
  6. Graphed distance to object = ______m
  7. % error for measured versus graphed distance = ______%
  8. Calculated distance to object using parallax angle = ______m
  9. % error for measured versus parallax distance = ______%
  1. Establish a baseline by placing 30cm of tape on the desk. Use the meter stick to make sure it is the correct length and straight. Record the “baseline” (a) in meters.
  2. Place the meter stick perpendicular to the baseline 15cm from one end of the tape.
  3. Place a pen/pencil next to the meter stick and record the distance to the baseline as the “measured distance to the object” (b) in meters. Remove the meter stick but be careful not to move the pen/pencil.
  4. Place the meter stick on the left side of the baseline so that it connects to the pencil/pen closest to the baseline and record angle A (c).
  5. Place the meter stick on the right side of the baseline so that it connects to the pencil/pen closest to the baseline and record angle B (d).
  6. Place a piece of graph paper in front of you so the short side of the paper is in front of you.
  7. Draw the baseline so that each square is 1cm. You should have a line 30 squares long.
  8. Place a protractor on the left side of the baseline, mark the angle and draw a straight line from the left side through the marked angle and continue across the paper.
  9. Place a protractor on the right side of the baseline, mark the angle and draw a straight line from the right side through the marked angle and continue across the paper.
  1. Count the squares from the baseline to where the lines cross and record the “graphed distance” (f) in meters.
  2. Calculate the percent error for the measured distance versus the graphed distance. And record your answer (g)

% error = (measured distance – graphed distance)/graphed distance x 100

  1. Measure the parallax angle C and record the angle (e).
  2. Calculate the distance by using parallax and record your answer (h).

Distance = Baseline x (57.3/parallax)

  1. Calculate the percent error for the measured distance versus the parallax distance. And record your answer (i)

% error = (measured distance – parallax distance)/parallax distance x 100

Extension:

Now using the set-up in class determine the distance to the sun model using parallax.