Astronomy midterm question: meridian zodiac sign at sunset?

Astronomy 210 Midterm 1, spring semester 2015
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board[*] was asked and answered:

f_14: Which constellation of the zodiac is highest in the sky at sunset tonight? Explain how you deduced the answer.
p_b: Gemini. The sun is now in Pisces today and since that constellation sets with the sun, at that point of time Gemini is at the zenith.

Discuss a plausible date and time for an observer in San Luis Obispo, CA to find these positions of Gemini and Pisces. If there is no such plausible date and time, then explain why. Defend your answer by clearly explaining how you used your starwheel to do this, along with any assumptions that you may have made.

[*] answers.yahoo.com/question/index?qid=20100916125243AABASB3.

Solution and grading rubric:

• p:
  Correct. Discussion for plausible date/time includes the following:
  1. determines when Pisces would be the sun-sign, by setting Pisces at the meridian, and finding the date what would correspond to 12 PM (March 30);
  2. sets Pisces on the west horizon of the starwheel such that it (and the sun) is setting;
  3. verifies that Gemini is at the meridian at that time on March 30 (around 7 PM).
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Has two of the three discussion points in (p).
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Has only one of the three discussion points in (p).
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some related discussion of using starwheel to find sun-signs, diurnal motion (rising/setting).
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 30676
Exam code: midterm01sh3P
p: 33 students
r: 8 students
t: 6 students
v: 5 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7495):
Another sample "p" response (from student 7495):