20090907

Astronomy quiz question: Virgo setting

Astronomy 210 Quiz 1, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Consider the view of the horizon shown below, as seen from San Luis Obispo, CA at a certain time on September 2. Ignore the fact that your starwheel does not include daylight savings time. Assume that you are able to see these constellations regardless if the sun is above the horizon or not.

How many hours pass until Virgo sets completely below the horizon?
(A) Three hours.
(B) Seven hours.
(C) 11 hours.
(D) 24 hours.

Correct answer: (C)

Using a starwheel, where the view shown above corresponds to 11:00 AM on September 2, Virgo will set on the west horizon at 10:00 PM, which is 11 hours later.

Response (A) corresponds to the hours for Virgo to completely set below the west horizon, starting from being just above the west horizon on September 2 (7:00 AM).

Section 70158
(A) : 11 students
(B) : 7 students
(C) : 32 students
(D) : 2 students

Success level: 64% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.72

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