Astronomy quiz question: September 16, 2016 partial lunar eclipse

Astronomy 210 Quiz 2, fall semester 2016
Cuesta College, San Luis Obispo, CA

A partial lunar eclipse will occur on September 16, 2016.[*] Observers in New Delhi, India will be able to see this eclipse while it happens, because they will be located:
(A) on Earth's daylight side.
(B) on Earth's night side.
(C) in the moon's penumbra.
(D) in the moon's negative shadow.
(E) in the moon's umbra.

[*] eclipsewise.com/oh/oh-figures/ec2016-Fig04.pdf.

Correct answer (highlight to unhide): (B)

For a partial lunar eclipse, the full moon is partially in both the umbra and in the penumbra shadow zones of Earth. All observers on the night side of Earth would be able to see the full moon during this partial lunar eclipse; however, observers on the daylight side of Earth would not.

(Observers in any of the moon's shadow zones (the umbra, penumbra, or "negative shadow" (antumbra)) during any type of lunar eclipse would then be located somewhere behind the dark side of the moon!)

Section 70158
Exam code: quiz02sr7Y
(A) : 4 students
(B) : 12 students
(C) : 18 students
(D) : 2 students
(E) : 4 students

Success level: 34% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55

Section 70160
Exam code: quiz02nYNy
(A) : 3 students
(B) : 3 students
(C) : 16 students
(D) : 6 students
(E) : 4 students

Success level: 16% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.22

Astronomy quiz question: next full moon after total lunar eclipse

Astronomy 210 Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

Observers in San Luis Obispo, CA will see a total lunar eclipse in the evening of September 27, 2015.[*][**] There will not be a total lunar eclipse in the following month because:
(A) the moon always keeps the same side facing Earth.
(B) the moon's orbit around Earth is tilted.
(C) the moon's orbit is not a perfect circle.
(D) Earth's axis precesses over a 23,000 year cycle.

[*] timeanddate.com/eclipse/lunar/2015-september-28.
[**] eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2015Sep28T.pdf.

Correct answer (highlight to unhide): (B)

When the moon is full and the moon's orbit is seen edge-on from the sun's perspective, there will be a total eclipse as the moon passes completely behind Earth, in Earth's umbral shadow. However, the moon's orbit will typically change its tilt such the subsequent full moon will no longer pass directly behind Earth, being either too high or low to pass into Earth's umbral shadow, making it just a regular full moon instead of a total lunar eclipse.

Response (A) explains why the near side of the moon appears to be constant; response (C) explains why some solar eclipses are annular rather than total; and response (D) is the reason why Polaris will not always be the pole star.

Section 70158
Exam code: quiz02s5Sz
(A) : 3 students
(B) : 25 students
(C) : 13 students
(D) : 1 student

Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

Section 70160
Exam code: quiz02Nnz2
(A) : 0 students
(B) : 16 students
(C) : 13 students
(D) : 0 students

Success level: 57% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

Astronomy in-class activity: eclipses

Astronomy 210 In-class activity 5 v.13.06.09, fall semester 2013
Cuesta College, San Luis Obispo, CA

Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet to discuss the categories and causes of different types of eclipses.

Presentation: eclipses

Cats casting shadows. Eh, this looks Photoshopped. How can you tell? What clues do you look for? As we'll see, it's not just the shadows cast by objects that are important, but where we are located relative to these shadows.

In the previous presentation, we discussed the motion and cycles of the moon--specifically lunar phases--and here we'll complete our discussion of the moon with eclipses.

Just a public service announcement about watching solar eclipses--make sure you are not looking directly at the sun with the unprotected eye. Either project an image of the sun using a pinhole, binoculars, or telescope...

...or use filters specifically labeled for observing the sun. My dog can practice safe solar eclipse viewing, and so should you.

First, the boring but necessary terminology.

Make sure you can distinguish between very similar terms:

• full and new moon (well, this should be self-explanatory).
• lunar eclipse and solar eclipse (light from the sun that would illuminate the full moon is blocked by Earth; direct light from the sun that would reach Earth is blocked by the moon).
• partial, total, and annular eclipse (sun or moon partially or totally covered/darkened, respectively; annular refers to an "annulus" or "little ring," where the moon is centered on the sun, but does not completely cover the sun).

Let's observe a simulation of a total lunar eclipse in April 14, 2014, as seen from the perspective of the sun. Note that Earth blocks light to the moon. Where would you have to be located (on Earth) to observe this total lunar eclipse? Where on Earth would observers not be able to see this total lunar eclipse? What phase is the moon in during this total lunar eclipse? (Why is there not a total lunar eclipse during every full moon?) (Video link: "1-5-140415-Lunar.mov.")

Here's a simulation of a total solar eclipse from July 11, 1991, again seen from the perspective of the sun, where the moon blocks light to Earth (casting a much smaller shadow). Where would you have to be located (on Earth) to observe this total solar eclipse? Where on Earth would observers not be able to see this total solar eclipse? What phase is the moon in during this total solar eclipse? (Why is there not a total solar eclipse during every new moon?) (Video link: "1-5-910711-Solar.mov.")

Time to do a picto-quiz--you'll be shown a picture or movie clip of the moon and/or sun (assume that each of these situations is the maximum extent of something being shadowed or blocked), and then be prompted with possible responses. At that point, if you know the correct answer, shout it out--because yes, the loudest answer is the most correct answer...

Is this a solar or lunar eclipse, or not an eclipse at all? Is this eclipse partial, total, or annular?

Is this a solar or lunar eclipse, or not an eclipse at all? Is this eclipse partial, total, or annular?

Is this a solar or lunar eclipse, or not an eclipse at all? Is this eclipse partial, total, or annular?

Is this a solar or lunar eclipse, or not an eclipse at all? Is this eclipse partial, total, or annular?

Is this a solar or lunar eclipse, or not an eclipse at all? Is this eclipse partial, total, or annular?

Is this a solar or lunar eclipse, or not an eclipse at all? How do you know that this is not an eclipse? What phase is this moon?

One more slide, for you Twihards--which team are you on? (Why is there no Team Bella?)

Second, let's consider why not every full moon is a lunar eclipse, and not every new moon is a solar eclipse.

This is a to-scale simulation of the moon revolving around Earth, while Earth revolves around the sun, as seen from the perspective of the sun. A lot goes on simultaneously, so just watch this and observe the different types of motions. After we discuss what details we should be looking for, we'll run this simulation again. (Video link: "1-5-Linesofnodes.mov.")

Note that the orbit of the moon is tilted, and the bright part is closest to us (the sun) and tilted downwards, while the dim part is farthest away from us, and tilted upwards. Which phase is the moon in right now? How do you know that an eclipse is not occurring right now? How do you know this?

The tilt of the moon's orbit changes slowly over time. Which phase is the moon in right now? How do you know that an eclipse is not occurring right now? How do you know this?

Generally an eclipse can happen only if (1) the moon is either new or full, and (2) the moon's orbit is aligned edge-on. Our previous two examples had the right phase, but wrong orbit; then the right orbit, but the wrong phase. Now we have both the right phase (although it is not clear whether it is new or full) and the right orbit (edge-on), and some type of eclipse (whether solar or lunar) is occurring right now. The timing between the moon phase and slowly changing moon orbit is crucial, and if the timing between these two cycles is not perfect (as it usually isn't), this is why there is not a solar or lunar eclipse every new or full moon.

Back to our simulation. When an eclipse happens (whether solar or lunar), you all say "now." Synchronize! Approximately how many months lapsed during this time? How many eclipses (whether solar or lunar) occurred during this time?

Let's look at two full moons, and flip between them. One is a (nearly) full moon that is just about to undergo a total lunar eclipse, and the other is a full moon that will not undergo any type of lunar eclipse. Can you determine the difference(s) between these two full moons?

Remember that the reason a lunar eclipse does not occur every full moon is that the orbit of the moon is usually tilted not edge-on, but too high or too low. Notice that the "Not to be eclipsed" moon has a slight shadow on the bottom, meaning that its orbit is too high, while the "To be eclipsed" moon has sharp edges at both top and bottom, meaning that its orbit is edge-on and will pass directly behind Earth for a total lunar eclipse. Next time just before the moon is completely full, take a careful look at the top and bottom edges of the moon (you will probably need binoculars or a telescope). If you see a slight ragged edge at the top or bottom, don't get too excited, as a total lunar eclipse is not impending.

In this promotional photograph for a certain obscure TV show from a few years ago, is it plausible that all these actors and actresses were present at in the studio at the same time? How do you know? What clues do you look for?

In the subsequent in-class activity, we'll be looking carefully at the different "shadow zones" cast by either the moon or Earth, and what would be observed if were located in each of these zones: umbra, penumbra, and antumbra (not a common term, we'll refer to the antumbra as the "negative shadow").

Astronomy quiz question: total solar eclipse location

Astronomy 210 Quiz 2, spring semester 2012
Cuesta College, San Luis Obispo, CA

An observer in San Luis Obispo, CA is watching a total solar eclipse. During this eclipse, the observer is located in:
(A) the moon's umbra.
(B) the moon's penumbra.
(C) the moon's negative shadow.
(D) Earth's umbra.
(E) Earth's penumbra.

Correct answer (highlight to unhide): (A)

For a total solar eclipse, the new moon is between the sun and Earth, blocking light the light from the sun. All observers in the umbra (the "complete" shadow zone) of the moon would have all sunlight blocked from reaching them, and thus they would see a total solar eclipse.

(Response (B) would be for a partial solar eclipse (assuming that is the maximum extent of its progress), response (C) would be for an annular solar eclipse. Responses (D) and (E) correspond to the location of the moon during a total and partial lunar eclipse, respectively.)

Section 30676
Exam code: quiz02SnT4
(A) : 20 students
(B) : 4 students
(C) : 7 students
(D) : 9 students
(E) : 1 student
(No response : 1 student)

Success level: 52% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.57

Astronomy quiz question: transit of Venus

Astronomy 210 Quiz 2, spring semester 2012
Cuesta College, San Luis Obispo, CA

In a rare event, the planet Venus will be observed in June 2012 as a tiny dark dot in the middle of the disk of the sun, for observers in San Luis Obispo, CA, who are located in:
(A) Venus' umbra.
(B) Venus' penumbra.
(C) Venus' negative shadow.
(D) Earth's umbra.
(E) Earth's penumbra.

Correct answer: (C)

During an annular solar eclipse, the angular size of the moon is (slightly) too small to completely cover the sun, as seen by an observer in the negative shadow zone (the antumbra) of the moon. This is similar to a transit of Venus, where its comparatively tiny angular size makes it appear to be a dot as it moves across the disk of the sun. Again as in an annular solar eclipse, the observer is in the negative shadow zone of Venus.

Section 30674
Exam code: quiz02n0Is
(A) : 14 students
(B) : 6 students
(C) : 7 students
(D) : 4 students
(E) : 3 students

Success level: 27% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.27

Astronomy flashcard question: total lunar eclipse

Astronomy 210, fall semester 2011
Cuesta College, San Luis Obispo, CA

Students were asked near the end of their learning cycle the following think-pair-share question, to be answered using flashcards.

While an observer in Seattle, WA is seeing a total lunar eclipse, an observer in San Luis Obispo, CA would see:
(A) a total lunar eclipse.
(B) a partial lunar eclipse.
(C) a normal full moon.
(D) (None of the above choices, as the moon would not be visible.)
(E) (Unsure/guessing/lost/help!)

Section 70160 (pre-)
(A) : 6 students
(B) : 10 students
(C) : 4 students
(D) : 0 students
(E) : 7 students

This question was asked again after students were instructed to discuss with a neighbor how they chose their answer, and to convince each other why their answer is (in)correct.

Section 70160 (post-)
(A) : 15 students
(B) : 12 students
(C) : 0 students
(D) : 0 students
(E) : 1 student

Correct answer: (A)

This was also asked as a midterm essay question in a previous semester.

Pre- to post- peer-interaction gains:
pre-interaction correct = 22%
post-interaction correct = 54%
Hake (normalized) gain <g> = 41%

Astronomy quiz question: cause of solar eclipses

Astronomy 210 Quiz 2, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

What causes a solar eclipse?
(A) The slow, gradual rotation of the moon about its own axis.
(B) Earth blocks light from the sun, casting a shadow on the moon.
(C) The moon blocks light from the sun, casting a shadow on Earth.
(D) Different amounts of the day and night sides of the moon as seen from Earth.

Correct answer: (C)

During a solar eclipse, the moon is between the sun and Earth, blocking Earth's view of the sun.

Section 30674
(A) : 1 student
(B) : 6 students
(C) : 35 students
(D) : 0 students

"Success level": 84% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

Astronomy quiz question: partial solar eclipse

Astronomy 210 Quiz 3, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

What would be seen by an observer on the side of Earth facing the moon, during a partial solar eclipse?
(A) A new moon that will not be big enough to entirely block the sun when it passes in front of it.
(B) A full moon that will appear a very, very dark brown-red.
(C) A full moon that will appear to be slightly dimmer than usual.
(D) A dark shadow across part of a full moon.
(E) The entire sun blocked by a new moon.
(F) Part of the sun will be blocked by a new moon.

Correct answer: (F)

During a partial solar eclipse, an observer on Earth will see the new moon covering a portion of the sun.

Section 30676
(A) : 16 students
(B) : 5 students
(C) : 4 students
(D) : 7 students
(E) : 4 students
(F) : 38 students
(Blank: 2 students)

Success level: 54% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.48

Previous post:
Astronomy quiz question: partial lunar eclipse, Spring Semester 2010.

Astronomy quiz question: annular/total solar eclipses

Astronomy 210 Quiz 2, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Why are some solar eclipses annular rather than total?
(A) The orbit of the moon around Earth is tilted with respect to the orbit of Earth around the sun.
(B) The orbit of the moon not a perfect circle, but is an ellipse.
(C) The moon rotates such that it always keeps the same side facing Earth.
(D) The direction of Earth's axis precesses over a 23,000 year cycle.

Correct answer: (B)

During a total solar eclipse, the moon blocks the entire sun, when observed from within the umbral shadow spot on Earth. However, due to the elliptical orbit of the moon, it may be unable to completely block the entire sun as seen from Earth, due to its distance from Earth being too far.

Response (A) explains why a total solar eclipse does not occur every time the moon is new. Response (C) explains why the near side of the moon is constant; response (D) is the reason why Polaris will not always be the pole star.

Section 70160
(A) : 25 students
(B) : 16 students
(C) : 0 students
(D) : 1 student

Success level: 43% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82

Astronomy midterm question: total solar eclipse locations

Astronomy 210 Midterm 1, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] At 10 AM, you are currently observing a total solar eclipse in San Luis Obispo, CA. Suppose you decided to call a friend who lives in Seattle, WA, which is north of San Luis Obispo, CA. Explain what kind of eclipse (if any) your friend would be able to see in Seattle, WA at the same time, or why not, using a diagram of Earth, the moon, and shadow zones. Assume that the skies are clear in both San Luis Obispo, CA and Seattle, WA.

(Adapted from a test bank question from Karl F. Kuhn, Theo Koupelis, In Quest of the Universe.)

Solution and grading rubric:

• p = 20/20:
  Correct. Draws a diagram clearly showing the umbral and penumbral shadow zones (in space and/or projected onto Earth's surface), showing San Luis Obispo, CA within a very small umbral "dot," and Seattle, WA either in or outside of the penumbra, with corresponding correct discussion of observing a partial solar eclipse, or no eclipse at all simultaneously. May have a technical error with showing an annular eclipse rather than a total eclipse, with San Luis Obispo, CA in the "negative shadow" (the antumbra) past the apex of the Moon's umbra.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Typically
  missing penumbra.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Discusses a partial solar eclipse in Seattle, WA, with little or no diagram, but with plausible arguments regarding scale of Sun, the Moon, and shadow zones.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Typically says Seattle, WA observer will experience a total solar eclipse simultaneously with or subsequent to the San Luis Obispo, CA observer, or incomplete diagram of some merit.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Involving unrelated factors.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30676
p: 16 students
r: 20 students
t: 12 students
v: 16 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, with a "not to scale" disclaimer (from student 0321):

Another sample "p" response, again with a "not to scale" disclaimer (from student 1987):

A "p" response that is drawn "perfectly" to scale (from student 2525):

A "p" response (from student 1192, impressed with a diagram which inexplicably includes a one-eyed Sun):

A sample "t" response, lacking a diagram (from student 1713):

A sample "v" response (from student 8008), claiming that the Seattle, WA observer will simultaneously be seeing a total solar eclipse:

Another sample "v" response (from student 3553), with a simultaneous lunar eclipse for the Seattle, WA observer:

A sample "v" response (from student 4143) with a partial solar eclipse for Seattle, WA, but with no diagram or further explanation other than schadenfreude:

Astronomy midterm question: total lunar eclipse versus total solar eclipse duration

Astronomy 210 Midterm 1, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Why does an observer see a total lunar eclipse lasting much longer than a total solar eclipse? Defend your answer using a diagram showing the positions of an observer, Earth, the moon, and shadow zones.

Solution and grading rubric:

• p = 20/20:
  Correct. The size of the umbra created by the Moon makes total solar eclipses last only a few minutes, as the umbral spot passes quickly over an observer's position. The size of the umbra created by the Earth makes total lunar eclipses last a few hours, as it will take that long for the Moon to pass through this shadow zone of the Earth. Has a correct explanation, and clear, correct diagrams of a total solar eclipse and a total lunar eclipse demonstrating the effect of umbra sizes.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Typically incomplete or inconsistent diagrams.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Diagrams problematic, but at least recognizes importance of sizes of umbrae.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Plausible arguments involving varying orbital speeds, precession of nodes, varying orbital distances, with some attempt at diagrams. Or substantively correct diagrams only.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Involving unrelated factors.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 30674
p: 8 students
r: 6 students
t: 7 students
v: 17 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 1959):

A sample "t" response (from student 1889):

A sample "v" response, with diagram only (from student 1213):

Astronomy quiz question: total solar eclipse, seen from the Moon

Astronomy 210 Quiz 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[4.0 points.] If observers in San Luis Obispo, CA, were observing a total solar eclipse, what would be seen by an observer on the side of the Moon facing Earth?
(A) A partial solar eclipse.
(B) An annular solar eclipse.
(C) The Sun, with no part of it being blocked by Earth.
(D) Circular umbral and penumbral shadow zones passing across the surface of Earth.

Section 30676
(A) : 7 students
(B) : 5 students
(C) : 6 students
(D) : 45 students

Correct answer: (D)

The Moon will be between Earth and the Sun during a total solar eclipse, and an observer on the side of the Moon facing the Earth will watch the Earth passing through the shadow of the Moon.

"Difficulty level": 73% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.59

Astronomy quiz question: total solar eclipse phase

Astronomy 210 Quiz 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[4.0 points.] What phase is the Moon in during a total solar eclipse?
(A) New.
(B) Full.
(C) (The phase depends on whether the total solar eclipse occurs at sunrise, midnight, or sunset.)
(D) (The Moon does not have a phase during a total solar eclipse.)

Section 30676
(A) : 29 students
(B) : 31 students
(C) : 1 student
(D) : 1 student
(No response: 1 student)

Correct answer: (A)

The Moon will be between Earth and the Sun, and thus will be new during a total solar eclipse.

"Difficulty level": 50% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.49

Astronomy quiz question: in the penumbra of the Moon

Astronomy 210 Quiz 2, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] An observer is located on the surface of the Earth, and this observer is also located in the penumbra of the Moon. What type of eclipse is seen by the observer?
(A) A total lunar eclipse.
(B) A partial lunar eclipse.
(C) An annular solar eclipse.
(D) A partial solar eclipse.
(E) A total solar eclipse.

Correct answer: (D)

Assuming that the umbra of the Moon never does pass over the observer (for which this would be response (E), a total solar eclipse), this will be only a partial solar eclipse. If the observer were in the "negative shadow" of the Moon (out past the umbra), then an annular solar eclipse would be observed (response (C)). Responses (A) and (B) correspond to the Moon itself being in the umbra or penumbra of the Earth, respectively.

Student responses
Section 70160
(A) : 5 students
(B) : 10 students
(C) : 0 students
(D) : 15 students
(E) : 3 students

"Difficulty level": 51%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.78

Astronomy clicker question: transit of Mercury

Astronomy 210, fall semester 2008
Cuesta College, San Luis Obispo, CA

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the middle of their learning cycle:

In a rare event, the planet Mercury was observed in November 2006 as a tiny dark dot in the middle of the disk of the sun, for observers in San Luis Obispo, CA. Which shadow zone were these observers in when that happened?
(A) The umbra of Mercury.
(B) The penumbra of Mercury.
(C) The negative shadow of Mercury.
(D) The umbra of Earth.
(E) The penumbra of Earth.
(F) (I'm lost, and don't know how to answer this.)

Section 70160
(A) : 7 students
(B) : 0 students
(C) : 16 students
(D) : 0 students
(E) : 2 students
(F) : 0 students

This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.

Section 70160
(A) : 1 student
(B) : 0 students
(C) : 25 students
(D) : 0 students
(E) : 0 students
(F) : 0 students

Correct answer: (C)

The negative shadow zone is directly behind the umbra of Mercury, where from that location its angular size is too small to completely cover the sun.

Pre- to post- peer-interaction gains:
pre-interaction correct = 64%
post-interaction correct = 96%
Hake (normalized) gain <g> = 89%

Astronomy midterm question: total lunar eclipse

Astronomy 10 Midterm 1, spring semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q2.4

At 7:30 PM at night, you are currently observing a total lunar eclipse in San Luis Obispo, CA. Suppose you decided to call a friend who lives in Seattle, WA, which is north of San Luis Obispo, CA. Explain what kind of eclipse (if any) your friend would be able to see in Seattle, WA at the same time, or why not, using a diagram of Earth, the moon, and shadow zones. Assume that the skies are clear in both San Luis Obispo, CA and Seattle, WA.

Solution and grading rubric:

• p:
  Correct. Clear and correct diagram of the observer, Earth, the moon and the sun shown. For a total lunar eclipse, the moon is completely in the umbra of Earth. All observers on the night side of Earth will be able to see this total lunar eclipse. Note that a total penumbral lunar eclipse may be discussed instead, as long as all observers on the night side of Earth see the same thing.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Earth-moon-sun diagram is essentially correct (showing a total lunar eclipse), but argument is based on observers being in different shadow zones, which is not possible, as all observers on the night side of Earth are in the umbra of Earth.
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Serious but flawed attempt at an Earth-moon-sun diagram, with major inconsistencies or errors, typically showing a total/partial/annular solar eclipse.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distributions:
Section 5166
p: 27 students
r: 4 students
t: 16 students
v: 18 students
x: 2 students
y: 0 students
z: 0 students

Notably this midterm was given during the umbral phase of the February 20, 2008 total lunar eclipse! Some students who had finished early were able to go outside and make Danjon L-scale ratings of the darkness of the umbral shadow on the Moon.

A sample of a "p" response (from student 0429) is shown below, clearly showing that observers in Seattle, WA and San Luis Obispo, CA would both see the Moon in the umbra of Earth:
Another "p" response (from student 1207) more elaborately illustrating the relevant geography:
Yet more elaborate geography in another "p" response (from student 1652):
An extended "p" response covering both total and partial lunar eclipse cases (from student 1886):

Astronomy quiz question: monthly solar and lunar eclipses

Astronomy 10 Quiz 2, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q2.4

[3.0 points.] Which one of the following choices best describes what would happen if the orbit of the Moon around the Earth was not tilted with respect to the orbit of the Earth around the Sun?
(A) There would never be any solar or lunar eclipses of any type.
(B) There would only be annular solar eclipses, and partial lunar eclipses.
(C) There would be a solar eclipse and a lunar eclipse every month.
(D) The Moon would then always block the Sun, making a permanent solar eclipse.
(E) The Earth would then always be between the Sun and Moon, making a permanent lunar eclipse.

Correct answer: (C)

The reason why there is no solar eclipse and lunar eclipse every month is that the orbit of the Moon around the Earth is tilted, such that the new Moon does not usually pass directly between the Sun and the Earth, and the full Moon does not usually pass directly between the Earth and the Moon.

Student responses
Section 4160
(A) : 4 students
(B) : 6 students
(C) : 25 students
(D) : 1 student
(E) : 3 students

Student responses
Section 5166
(A) : 5 students
(B) : 6 students
(C) : 50 students
(D) : 3 students
(E) : 2 students