We will be using
protractors to measure angles. Protractors will be set out by the instructor.

Sub Tasks:

  1. The figure below (local link / general link: howto_protractor.html) shows how to use a protractor---study it.
  2. Let's do a quick example angle measurement (detailed in the following list items) with a protractor.
  3. Draw three dots NOT in a line on this page and label them Earth, planet, Sun. The dots should be about 1/4 of a page apart. It's OK that they will overlap the text.

    My Answer: My diagram, NOT yours. Draw your own with a DIFFERENT angle.

    Earth ------------------ Planet

  4. Draw lines from the Earth to the two other astronomical objects and extend the lines so that they are longer than the radius of the protractor.
  5. Put the protractor center on the Earth.
  6. Align the protractor axis with the Sun.
  7. Read off the angle to the planet. The angle is ________ . My Answer: 90°. Your answer must be different.
  8. This angle is called the elongation of the planet.
  9. The elongation is usually measured from 0° to 180° east or west of the Sun. DIRECTION must be specified.
  10. East is counterclockwise and west is clockwise when viewing the Solar System from the north celestial pole (NCP) side of the ecliptic plane.
  11. Assuming you are on the NCP side of the ecliptic plane, the elongation you measured is ________ . My Answer: 90° E. Your answer must be different.
  12. Now find the angle from the Sun to the Earth subtended at the planet. The angle together with its east/west direction is ___________________ . My Answer: ∼ 30° W. Your answer must be different.
  13. This angle is called the astronomical phase angle (or phase angle for short).
Local file:
local link: howto_protractor_task.html.
File: Howto file: howto_protractor_task.html.