Astronomy midterm question: Libra sun-sign with Gemini rising

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:
??: Okay, I have a Libra sun-sign and a Gemini rising sign. Someone please explain what they mean!
fk: The sun sign is technically the sign the sun was in on the day you were born, and the rising sign was the sign rising on the horizon at the time of day you were born.
Discuss a plausible date and time for an observer in San Luis Obispo, CA to find the sun in Libra, with Gemini rising. 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=1006041109420.

Solution and grading rubric:
  • p:
    Correct. Discussion for plausible date/time includes the following:
    1. determines when Libra would be the sun-sign, by setting Libra at the meridian, and finding the date what would correspond to 12 PM (November 10);
    2. sets Gemini on the east horizon of the starwheel such that it is rising;
    3. looks at the time (around 8 PM to 9 PM) on November 10 that corresponds to when Gemini would rise.
  • 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). May find when Libra is the sun-sign, but adds additional restriction that Libra (and the sun) must still be visible in the sky when Gemini is rising, which is not possible.
  • 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:
Grading distribution:
Section 30674
Exam code: midterm01nR31
p: 4 students
r: 22 students
t: 11 students
v: 0 students
x: 1 student
y: 0 students
z: 0 students

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

A sample "r" response (from student 7897) discussing Gemini setting, instead of rising:

A sample "r" response (from student 0104), with a diagram showing Gemini setting (and not rising):

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