Astronomy quiz question: starrise to starset time

Astronomy 210 Quiz 1, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] A star that rises from the northeast horizon in San Luis Obispo, CA will take approximately how many hours until it sets in the northwest horizon?
(A) Less than 12 hours.
(B) More than 12 hours.
(C) (It cannot be determined how many hours the star will take to set, unless the season is known.)
(D) (None of the above choices, as it is not possible for a star to rise from the northeast horizon in San Luis Obispo, CA.)

Correct answer: (B)

Using a starwheel, selecting any star (e.g., Pollux) that rises from the northeast horizon, and finding the difference in times when it is on the northeast horizon, and eventually setting on the northwest horizon on the same/consecutive day(s) will result in more than 12 hours elapsed. (For Pollux, it rises at 2:00 AM on August 25, and will set at 5:30 PM later that same day.) Or from discussion on paths of the sun, objects that rise north of east will take longer than 12 hours to rise and set, compared to objects that rise directly in the east (exactly 12 hours); or objects that rise south of east (less than 12 hours).

Student responses
Section 70160
(A) : 12 students
(B) : 10 students
(C) : 8 students
(D) : 1 student
(no response) : 1 student

"Difficulty level": 38%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.44