Astronomy quiz question: Saturn in retrograde

Astronomy 210 Quiz 2, fall semester 2014
Cuesta College, San Luis Obispo, CA

The diagram at right shows Saturn's position in the constellation Libra as seen by an observer in San Luis Obispo, CA. Saturn is currently undergoing retrograde motion. The following night Saturn will be __________ this position in the constellation Libra.
(A) slightly to the left of.
(B) slightly to the right of.
(C) exactly at.
(D) (Not visible at all the following night.)

Correct answer (highlight to unhide): (B)

When Saturn is undergoing prograde motion, it will move from west to east (in this perspective, right to left, as shown in blue) with respect to the background stars over consecutive nights. When Saturn is undergoing retrograde motion, it will move from east to west (in this perspective, left to right, as shown in red) with respect to the background stars over consecutive nights.

Section 70158
Exam code: quiz02n3w7
(A) : 15 students
(B) : 24 students
(C) : 3 students
(D) : 0 students

Success level: 59% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.74

Section 70160
Exam code: quiz02k3pL
(A) : 9 students
(B) : 20 students
(C) : 5 students
(D) : 0 students

Success level: 61% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.56