Astronomy quiz question: August 2017 partial solar eclipse in San Luis Obispo, CA

Astronomy 210 Quiz 2, spring semester 2017
Cuesta College, San Luis Obispo, CA

A total solar eclipse will occur on August 21, 2017 for many observers in the United States[*]. During this event, observers San Luis Obispo, CA will only see a partial solar eclipse[**], because they will be 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.

[*] eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2017Aug21Tgoogle.html.
[**] timeanddate.com/eclipse/in/usa/san-luis-obispo?iso=20170821.

Correct answer: (B)

An observer in the moon's penumbra will see a partial solar eclipse, while an observer in the moon's umbra will see a total solar eclipse. (The "negative shadow" refers to the antumbra of the moon.)

Section 30674
Exam code: quiz02n1hT
(A) : 2 students
(B) : 17 students
(C) : 0 students
(D) : 2 students
(E) : 2 students

Success level: 76% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

Section 30676
Exam code: quiz02sNoO
(A) : 3 students
(B) : 28 students
(C) : 1 student
(D) : 3 students
(E) : 7 students

Success level: 69% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64

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 quiz question: position of moon during October 2014 total lunar eclipse

Astronomy 210 Quiz 3, fall semester 2014
Cuesta College, San Luis Obispo, CA

Observers in San Luis Obispo, CA will see a total lunar eclipse in October 2014.[*] During the total lunar eclipse, the moon will be 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.

[*] http://eclipse.gsfc.nasa.gov/OH/OHfigures/OH2014-Fig03.pdf.

Correct answer (highlight to unhide): (D)

During a total lunar eclipse, light from the sun that illuminate the full moon would be completely blocked by Earth, when the moon is completely within Earth's "complete shadow," or its umbra. (Note that since the textbook shows but does not specifically name the moon's antumbra, it is referred to as the moon's "negative shadow" for the purposes of discussion in this class.)


Section 70158
Exam code: quiz03s8tE
(A) : 5 students
(B) : 2 students
(C) : 2 students
(D) : 23 students
(E): 7 students

Success level: 57% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.81

Section 70160
Exam code: quiz03n6n4
(A) : 5 students
(B) : 4 students
(C) : 1 student
(D) : 19 students
(E): 5 students

Success level: 57% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.49

Astronomy quiz question: August 2017 partial/total solar eclipse in St. Louis, MO

Astronomy 210 Quiz 2, spring semester 2013
Cuesta College, San Luis Obispo, CA

In August 2017, observers in different neighborhoods of St. Louis, MO will either observe a partial solar eclipse or a total solar eclipse[*], depending on whether they are located in the moon's __________ or __________, respectively.
(A) negative shadow; penumbra.
(B) negative shadow; umbra.
(C) penumbra; negative shadow.
(D) penumbra; umbra.
(E) umbra; negative shadow.
(F) umbra; penumbra.

[*] eclipse2017.org/2017/maps/cities/STL.htm.

Correct answer: (D)

An observer in the moon's penumbra will see a partial solar eclipse, while an observer in the moon's umbra will see a total solar eclipse. (The "negative shadow" refers to the antumbra of the moon.)

Section 30674
Exam code: quiz03Ne3v
(A) : 4 students
(B) : 4 students
(C) : 0 students
(D) : 14 students
(E) : 1 student
(F) : 7 students
(No response: 1 student)

Success level: 47% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.23

Section 30676
Exam code: quiz02Sl1v
(A) : 5 students
(B) : 4 students
(C) : 8 students
(D) : 15 students
(E) : 5 students
(F) : 5 students

Success level: 41% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.73

Astronomy quiz question: annular solar eclipse, total lunar eclipse observer locations

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

[Version 1]
An annular solar eclipse was observed on May 2012 by observers in Northern California, who were 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: (C)

The observers must be located in the moon's antumbra (or "negative shadow") to see the middle of the sun blocked, but the edges still visible.

Section 70158
Exam code: quiz02k3P7
(A) : 12 students
(B) : 10 students
(C) : 5 students
(D) : 5 students
(E) : 2 students
(More than one response) : 1 student

Success level: 19% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.20

[Version 2]
A total lunar eclipse was observed on December 2011 by observers in San Luis Obispo, CA.  During that time, the moon was located in:
(A) Earth's umbra.
(B) Earth's penumbra.
(C) Earth's negative shadow.
(D) (none of Earth's shadow zones.)

Correct answer: (A)

During a total lunar eclipse, the moon is located entirely within Earth's umbra in order for light from the sun to be be completely blocked from reaching the moon (ignoring light scattered by Earth's atmosphere).

Section 70160
Exam code: quiz02n3Ap
(A) : 23 students
(B) : 7 students
(C) : 0 students
(D) : 1 student

Success level: 75% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46

Astronomy quiz question: annular solar eclipse observed from the moon

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

Consider a side view of Earth and its shadow zones, and the moon and its shadow zones.  The sun is located to the left, far off of the page.  An observer on the side of the moon facing Earth would see:

(A) the sun, with no part of it being blocked.
(B) the sun, with part of its edge being blocked.
(C) the sun, entirely blocked.
(D) the edges of the sun, with the middle of it blocked.
(E) Earth, completely illuminated by the sun.
(F) Earth, illuminated with a small circular shadow on it.
(G) Earth, completely darkened.

Correct answer: (F)

The observer is on the side of the moon facing away from the sun, so this eliminates responses (A)-(D), which would only be observed on the side of Earth (or the moon) facing the sun.  The moon's antumbra (or "negative shadow") will only mask a small portion of Earth, with the remainder of Earth remaining illuminated in the moon's penumbra (in which only a portion of the sun's disk is blocked), or outside.   (Note that this diagram is not intended to be to scale.)

Section 70158
Exam code: quiz02k3P7
(A) : 0 students
(B) : 1 student
(C) : 1 student
(D) : 0 students
(E) : 3 students
(F) : 28 students
(G) : 2 students

Success level: 81% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.10

Section 70160
Exam code: quiz02n3Ap
(A) : 0 students
(B) : 2 students
(C) : 1 student
(D) : 1 student
(E) : 5 students
(F) : 18 students
(G) : 4 students

Success level: 61% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.27

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 quiz question: cause of lunar eclipses

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

What causes a lunar 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: (B)

During a lunar eclipse, the moon is in Earth's shadow, on the opposite side of Earth than the sun.

Section 30676
(A) : 2 students
(B) : 32 students
(C) : 13 students
(D) : 0 students

"Success level": 70% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

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: 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%