P-dog's blog: boring but important: 202003

20200316

Astronomy midterm question: Great Square and Big Dipper just after sunset

Astronomy 210 Midterm 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

An online astronomy magazine article describes the positions of the "Great Square" (located between the constellations Andromeda and Pegasus) and the Big Dipper just after sunset:[*]:

After dark now the Great Square [between Andromeda and Pegasus] is declining low in the west, tipped onto one corner. Meanwhile the Big Dipper is creeping up in the northeast, tipped up on its handle.

Discuss a plausible date and time for someone in San Luis Obispo, CA to make this observation of the Great Square and the Big Dipper in the early evening sky. 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. (Ignore daylight saving time.)

[*] skyandtelescope.com/observing/sky-at-a-glance/.

Solution and grading rubric:

p:
Correct. Discussion includes the following:
1. locates the Great Square and the Big Dipper asterisms on the starwheel, and rotates starwheel such that the Great Square is just above the west horizon, while the Bigger Dipper is near the northeast horizon; and
2. selects a time that is dark enough to see stars in the early evening (somewhere between 7 PM and 10 PM or so); and
3. looks up a specific date corresponding to that early evening time.
r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May have selected midnight, sunrise or some other time of night not convincingly "after dark," "just after sunset" or an "early evening" time.
t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. May have Great Square near east horizon, and Big Dipper near the west horizon.
v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use starwheel in a systematic manner.
x:
Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on using a starwheel in a systematic manner.
y:
Irrelevant discussion/effectively blank.
z:
Blank.

Grading distribution:
Section 30674
Exam code: midterm01n7in
p: 21 students
r: 5 students
t: 3 students
v: 1 student
x: 0 students
y: 0 students
z: 0 students

Section 30676
Exam code: midterm01S7wY
p: 27 students
r: 11 students
t: 2 students
v: 3 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 2020):

Astronomy midterm question: "sliced" moon rising with coming darkness

Astronomy 210 Midterm 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

The following excerpt describes the rising of a crescent ("sliced") moon around sunset:

Darkness was coming slowly down, a cool cloak draped over them. Soon, a sliced moon began to rise as a wind rose.

Discuss whether or not this description is plausible for an observer in San Luis Obispo, CA, and how you know this. Support your answer using a diagram showing the positions of the sun, moon, Earth, and an observer on Earth.

[*] Mitchell Smith, Moonrise: Book Three of the Snowfall Trilogy, Tom Dougherty Associates (2004), p. 195.

Solution and grading rubric:

p:
Correct. Complete diagram (with the sun, moon, and observer on Earth), and discusses one of the following reasons why this description would be implausible:
1. waxing crescent moon is overhead at 3 PM, and rose six hours earlier at 9 AM; while waning crescent moon is overhead at 9 AM, and rose six hours earlier at 3 AM, such that neither of these crescent phase moons could be rising just after sunset; or
2. the moon phase that would be rising around/at/after sunset (6 PM) would be the waxing gibbous moon, full moon or waning gibbous moon, such that no crescent phase moon could be rising after sunset.
r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Diagram and/or explanation has minor errors.
t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram or discussion.
v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to draw a moon phase diagram and apply rise/overhead/set times.
x:
Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on a moon phase diagram.
y:
Irrelevant discussion/effectively blank.
z:
Blank.

Grading distribution:
Section 30674
Exam code: midterm01n7in
p: 15 students
r: 3 students
t: 4 students
v: 5 students
x: 0 students
y: 0 students
z: 0 students

Section 30676
Exam code: midterm01S7wY
p: 24 students
r: 2 students
t: 5 students
v: 9 students
x: 5 students
y: 0 students
z: 0 students

A sample "p" response (from student 2310):

Astronomy midterm question: Venus setting while Jupiter rising at night?

Astronomy 210 Midterm 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

The following excerpt describes a night where Venus is setting while Jupiter is rising[*]:

Let me try to recall what has happened, the amusing and strange, and sad and terrible scenes witnessed in these last few days. On my first night at sea, I watched Venus slowly sinking into the sea, and Jupiter rising...

Discuss a plausible time (around sunset, midnight, or sunrise) that these two planets would be observed in San Luis Obispo, CA, and how you know this. Support your answer using a diagram showing the positions of the sun, Venus, Jupiter, Earth, and an observer on Earth.

[*] J.C., "Wrecked--A Week on Sable Island," The Canadian Methodist Magazine, vol. XV (January-June 1882), p. 73.

Solution and grading rubric:

p:
Complete diagram and reasoning where observer on Earth must be at sunset to watch Venus (in an inner orbit) setting while Jupiter (in an inner orbit) rises in the east.
r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Typically diagram and/or supporting argument is contradictory or incomplete.
t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Still has Venus in an inner orbit and Jupiter in an outer orbit around the sun.
v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some attempt at diagram(s), but no clear indication of observer/horizon on Earth and/or placement of inner planets. Typically misplaces Venus and Jupiter in their relative inner/outer orbits around the sun, or has Venus and Jupiter orbiting Earth.
x:
Implementation/application of ideas, but credit given for effort rather than merit.
y:
Irrelevant discussion/effectively blank.
z:
Blank.

Grading distribution:
Section 30674
Exam code: midterm01n7in
p: 14 students
r: 1 student
t: 6 students
v: 7 students
x: 1 student
y: 0 students
z: 1 student

Section 30676
Exam code: midterm01S7wY
p: 24 students
r: 0 students
t: 13 students
v: 6 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 2000):