Cuesta College, San Luis Obispo, CA
[20 points.] An astronomy question on an online discussion board(*) was asked and answered:
donc:You are planning to do some evening ocean sailing some time in the near future. Because of scheduling conflicts, the only time that you can sail is 9:00 PM. Since you would like to have the moon in the sky to help you navigate, what phases could the moon be?Discuss whether or not this answer is correct, and how you know this. Support your answer using a diagram showing the positions of the sun, moon, Earth, and an observer on Earth.
DH: [F]irst quarter...
Solution and grading rubric:
- p = 20/20:
Correct. The first quarter moon is highest overhead for an observer at 6:00 PM on Earth, setting six hours later at midnight, so would still be above the horizon at 9:00 PM. Correct diagram and reasoning.
- r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses how diameter affects either light-gathering power or resolving power, other diameter/power discussion incomplete.
- t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram or discussion.
- v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Substantive discussion, but missing/problematic diagram.
- x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. Problematic discussion, diagrams with the moon orbiting the sun, etc.
- y = 2/20:
Irrelevant discussion/effectively blank.
- z = 0/20:
Exam code: midterm01neE7
p: 14 students
r: 6 students
t: 3 students
v: 4 students
x: 6 students
y: 0 students
z: 0 students
A sample "p" response (from student 0401):
Another sample "p" response (from student 0010):