Section 3:

Analyzing Images to Find an Asteroid’s Rotation Rate


Part 3A: Introduction

Teachers/Leaders: Notes and Help Section3 Part A-E


Let’s do a quick REVIEW of Section 1 and Section 2:


  • focused on using Quorum to command Skynet to request CCD camera images of objects in space.


  • focused on understanding and using the software, Afterglow Access, to examine one, or at most, two images at a time.

What will SECTION 3 teach us?

  • This section will focus on gathering data from an image to measure an object’s brightness (the apparent magnitude).
  • We will then see how computers are used to analyze and display the data – in this case, a light curve.
  • Afterglow Access will provide most of the tools we need.

**REVIEW Questions**

In Section 2, you found the rotational period of a model asteroid (recall the potato).

In your journal, answer the following two questions:

1. Without looking back, write a definition for rotational period.

2. Then, briefly describe what information you would need to find the rotational period of a REAL asteroid (Hint: look at the goals of section 3 below).


Chris introduces Section 3 in this 3:23 video.



You have already learned to do a lot of astronomy. Congratulations! You can
  • 1. Request images of an object (Section 1)
  • 2. Locate an asteroid in an image (see Part Q of Section 2)
  • 3. Use Quorum commands on matrices to model how image processing software works behind the scenes.

Let’s now tackle the following goals

Section 3 GOALS:

  • 1. You will learn about apparent magnitude and how it relates to the idea of photometry.
  • 2. You will learn about the different types of photometry and which type is appropriate to measure the brightness of an asteroid.
  • 3. You will compare the brightness of an asteroid to the brightness of a well-known source called a standard star using a math equation in Quorum.
  • 4. Using Afterglow Access, you will learn how to photometer an asteroid and standard star across a series of images taken during one night.
  • 5. You will learn how to download and interpret this photometry data from Afterglow Access. Apparent magnitude shows up in this data.
  • 6. You will then construct a graph of the change in brightness (apparent magnitude) vs time for your series of asteroid observations. This graph is the light curve of the asteroid.
  • 7. You will then interpret the light curve of your asteroid to find and verify its rotation period.

Let’s get started!