20160824

Online reading assignment: flipped classroom, motions and cycles (SLO campus)

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

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on Earth's rotation/precession/revolution/tilt, the moon's motions and cycles, and watching two video presentations on the flipped class: "What Is the Flipped Class?" and "How the Flipped Classroom Works."

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"In the slide presentation you asked us to ponder the word 'zodiac.' I want to understand why since the beginning of time people based not only their direction or time on the sky the stars, cycles of the moon but they based personality, or behavior what type of animal they would most resemble all off the revolution of Earth around the sun. I think that is fascinating."

"That Earth's spin axis wobbles, causing it to take 26,000 years to complete."

"'Pole wandering'--I am fascinated by the fact that in previous eras there were different north stars."

"The specific names for the moon's phases was pretty interesting for me. I understood the basic movement of Earth and the moon but the names of the phases were pretty cool for me to learn."

"That Earth is almost always the same distance from the sun due to the fact Earth's orbit is nearly circular, not elliptical. And seasons are more due to the solar energy the Earth experiences and not due to variation of the distance from the sun."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Precession vs. rotation was a bit confusing to understand as they are both related to motion but mean two different things."

"I found it difficult trying to visualize all of the different motions of Earth, sun and moon. Because I had a hard time visualizing them it made it difficult to distinguish between them all in my head."

"Zodiac signs still get me--not sure what they really mean or if they really do mean anything..."

What date would Virgo be just above the east horizon, as seen by an observer at 11 PM in San Luis Obispo, CA? (Ignore daylight saving time.)
February 20.  ********************* [21]
April 25.  [1]
July 4.  [0]
August 20.  [0]
(Unsure/guessing/lost/help!)  ****** [6]

Match these cycles with their approximate duration.
(Only correct responses shown.)
Earth's rotation: 24 hours [89%]
Earth's revolution: one year [82%]
Earth's precession: 26,000 years [96%]
The moon's revolution: one month [79%]

Place these moon phases in chronological order in their cycle (starting with new moon).
(Only correct responses shown, in unscrambled order.)
New moon: first [89%]
Waxing crescent: second [79%]
First quarter: third [75%]
Waxing gibbous: fourth [71%]
Full moon: fifth [71%]
Waning gibbous: sixth [82%]
Third quarter: seventh [75%]
Waning crescent: eighth [71%]

Explain what is different about homework in a flipped class.
"I feel like there wouldn't be as much tedious work. Usually homework is tedious busy work that takes a long time to complete but after a flipped classroom lecture there would maybe be less time spent doing homework because of a better understanding of the material."

"Flipped class allows for you to engage in the work for a class via a video that is able to be watched before class starts. Once you have watched this video you will have a rough understanding of what will be learned in your next class meeting allowing for more one-on-one help and assistance in the actual classroom environment. This allows students to work at their own pace and also receive help on things they don't understand when around their professors."

"The homework is to review the information that the in class activities will be based on."

Describe where/when most student learning occurs in a flipped class.
"Most the learning of lessons would be done studying by the students outside the class watching videos. Then teachers can focus on working with students one and one and answering specific questions."

"Students in a flipped class are going to learn the most during class time because they go into that environment with the lecture already in mind. They use that time to apply what they've learned, clarify, converse, and immerse themselves in the material. Conventional classes tend to flood students with information during class time and students have to do the learning during their homework time."

"In a flipped class, students learn the most before and during the lecture, whereas in the conventional class, students learn the most during or after the lecture, or just struggle because some learn at a different pace than others."

Pick one piece of student advice from the previous semester, and discuss why you agree (or disagree) with it.
"Several of the advice quotes were along the lines of 'do the online reading assignments.' I really agree with this because they make the lecture for that week so much easier to understand. I was lost the first day, but then I started doing the online reading and it was much better, much clearer."

"I agree with the importance of showing up to class. Missing a day causes you to fall behind speaking from experience which causes great deals of stress."

"'Do all of the previous semesters' archived quizzes and midterms.' This seems really helpful to being successful in the course. I wasn't even aware that you had the old quizzes and tests available to study until I read that."

"'As long as you figure out how to study for this class it isn't as hard as it seems initially.' I agree with this student advice because you can tell students to study and go to class and read their textbook and stuff (which I fully agree with), but in the end it really comes down to understanding what the teacher/professor expects you to understand. Once you get an idea of how the teacher evaluates your knowledge you'll get a hang of it pretty quickly."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Because I didn't have the textbook yet and couldn't answer all the questions accordingly will I still get credit for trying to answer them?" (Yes, as long as you tried your best.)

"Could we go over how to navigate your site/blog and where to find links/sections?" (We can review that to remind you about next week's homework, and to study for the upcoming quiz.)

"I like the flipped classroom style, this makes learning less stressful and helps the teacher tailor discussions to content most needed by students."

"Do you think Cuesta College could do a total flip for all its classes?" (I would surprised if that would happen, as at least from my experience there is a lot of instructor preparation to teach a flipped class.)

"I love the energy and excitement you have already displayed in this course, just in the first lecture. After last semester, I swore off night classes after having a rough experience with a math course. However, once I stepped foot out of the lecture last Wednesday, I instantly felt relieved. Never during the course of the class was I disengaged, staring at the clock, or snoozing off. You are the best instructor to handle this course. I am so excited to experience astronomy alongside someone so passionate about the material. Keep it up!"

Online reading assignment: motion

Physics 205A, fall semester 2016
Cuesta College, San Luis Obispo, CA

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on the reading textbook chapters and previewing a flipped class presentation on (constant acceleration) motion.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"When dealing with equations of kinematics you need to know certain elements of the equation in order to solve for the final piece. Given that information you would then choose which equation to use."

"There are five different equations that were mentioned in the reading that can help in solving problems that deal with a combination of initial and ending velocity, displacement, acceleration, and time."

"For specific situations you need to dissect them individually to see which equation you need to use. Some equations have different factors and according to these different factors depends on the equation that is needed."

" I also understand the 'chain of pain' and how we can connect all three key quantities such as position, velocity, and acceleration. I also have a full understanding of what all the symbols presented in the presentation preview mean."

"I feel like I am very comfortable with kinematics and I understand all of the concepts. I haven't had time to practice using the equations yet, but once I do a few practice problems I should have the material down."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"I am still a little confused in the differences between both tangent and chord slopes as well as instantaneous and average velocity/acceleration. I need the 'chain of pain' explained to me a little better because it almost makes these concepts harder than they actually are."

"I'm not sure how the graphs work."

"The slopes and equations made me a little crazy."

"I found it confusing when to use which equations for constant acceleration."

"I understand but need to practice using equations when given different variables."

"It took me a long time to realize what the variables stood for... I do not know what a chord slope is, and I will need to look over the 'chain of pain' graph longer to understand it. (I know the graph is meant to be self explanatory, but without a decently large amount of time, for me it isn't."

Briefly describe the difference(s) between a chord slope and a tangent slope on a graph.
"Chord slope is the slope of a line segment crossing at least two points of a graph of a function. Tangent slope is derived from the slope of a line that touches the graph of a function at exactly one point."

"On a position versus time graph, tangent slope determines the instantaneous velocity and the chord slope determines the average velocity."

"I'm still pretty confused by this one."

Mark the level of your exposure to (basic calculus) concepts of derivatives/integrals.
None at all.   ********* [9]
Slight.   ************ [12]
Some.   ************ [12]
A fair amount.  ******* [7]
A lot.   ****** [6]

Indicate how each of these quantities are determined from kinematic graphs.
(Only correct responses shown.)
Displacement ∆x: area under a vx(t) graph. [50%]
Position x: (None of these choices.) [26%]
Change in (instantaneous) velocity ∆vx: area under an ax(t) graph. [44%]
(Instantaneous) velocity vx: tangent slope of an x(t) graph. [43%]
Average velocity vx,av: chord slope of an x(t) graph. [37%]
(Instantaneous) acceleration ax: tangent slope of a vx(t) graph. [46%]
Average acceleration ax,av: chord slope of a vx(t) graph. [50%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can we briefly go over the kinematic graphs to get a better grasp of the 'chain of pain?'"

"Could you go over some examples of when to use the kinematic equations, and that whole 'hell network' thing or whatever you called it."

"I like when you do examples on the board for challenging or difficult concepts. I learn the material best that way." (As long as you let me know that's what you need to see in class, then yes, I'll try to fit in more examples.)

"Can we expect to have two reading assignments and two homework reports every week, due both before each Monday and Wednesday?" (Yes, except for weeks with holidays, or midterms.)

"How do we see what scores we are getting on these reading assignments?" (They'll be posted on the course website after each quiz.)

"Mystic, Instinct, or Valor?" (Actually, I'm with the Enlightened. #donotresist #toresististofighttheinevitable)

"Not really getting these graphs. But I like my lab instructor. He's cooler than you, to be honest." (#smh)

20160823

Online reading assignment: flipped classroom, motions and cycles (NC campus)

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

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on Earth's rotation/precession/revolution/tilt, the moon's motions and cycles, and watching two video presentations on the flipped class: "What Is the Flipped Class?" and "How the Flipped Classroom Works."


Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"How you can tell where the stars are at any given date or time in the sky by using the starwheel."

"That Earth slowly tilted over 26,000 years, and that for the majority of the 26,000 year cycle there isn't a 'north star.'"

"The flipped classroom--this is the first time I've been in a class that has used this method and from what I see, I'm a big fan and I'm interested in how I'll do in it."

"That stars are present in the sky even in daytime not just nighttime."

"That Earth is revolving, rotating and precessing all at the same time. I never really think about Earth as actively moving because it does not feel like it is."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"How the seasons change based on the solar energy received from the sun, not on Earth's distance away from the sun."

"I'm still confused about the starwheel. I am still having issues locating the stars when given the date and time."

"Precession--why does Earth do it? Did an asteroid hit the earth at a critical time for this to happen?"

"The names of the phases of the moon. And putting them in order."

What date would Virgo be just above the east horizon, as seen by an observer at 11 PM in San Luis Obispo, CA? (Ignore daylight saving time.)
February 20.  **************** [16]
April 25.  [0]
July 4.  [0]
August 20.  * [1]
(Unsure/guessing/lost/help!)  *********** [11]

Match these cycles with their approximate duration.
(Only correct responses shown.)
Earth's rotation: 24 hours [96%]
Earth's revolution: one year [89%]
Earth's precession: 26,000 years [93%]
The moon's revolution: one month [89%]

Place these moon phases in chronological order in their cycle (starting with new moon).
(Only correct responses shown, in unscrambled order.)
New moon: first [93%]
Waxing crescent: second [64%]
First quarter: third [17%]
Waxing gibbous: fourth [17%]
Full moon: fifth [75%]
Waning gibbous: sixth [64%]
Third quarter: seventh [57%]
Waning crescent: eighth [46%]

Explain what is different about homework in a flipped class.
"The main difference is that it allows students to go over the material as many times as needed before the class period and allows students to check their understanding and extend learning after class."

"In a flipped class, one should complete the assignments before the class period to participate effectively in the classroom assignments."

"The homework includes presentations which would normally be showed and lectured upon in class."

Describe where/when most student learning occurs in a flipped class.
"Some people learn by either doing or seeing so it's effective for students to watch the videos without any anxiety issues and can rewind the videos as many times as they want to fully understand it."

"Most student learning should occur at home or in their personal time so then the teacher can provide help in class during a flipped-class setting."

"In class because they can get one on one time with the instructor and get clarification from questions they might have from presentations ahead of time making it easier to keep up with the class."

"Students learn more when they are able to ask questions on difficult material."

Pick one piece of student advice from the previous semester, and discuss why you agree (or disagree) with it.
"I completely agree that reading the book before class can maximize the learning potential of the next class period because the information is fresh in your mind."

"I liked, 'for the love of God, read the textbook.' You never know if the reading is actually necessary for a class or if it's just assigned to prove that the teacher gives homework and you can get away without doing it. I appreciate the warning."

"'Study, study , study...' Repetition is key to remembering. I agree with this because I have a hard time remembering anything."

"The advice you I got is that I have to put a lot of effort if I want to succeed."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"What you can recommend for me in order to understand the material in a better way?" (Practice with the additional questions on the flashcard question packets, which includes many questions from actual past quizzes.)

Are we going to have to memorize the names of certain constellations and what they look like? Also, are the flashcard question packets homework that we print out and turn in?" (You don't need to memorize the constellation shapes and names, but you should be familiar enough with them to locate them on your starwheel. The flashcard question packet is just a resource we'll use to ask questions in class; and many of these questions are from quizzes from previous semesters, so going over the questions we don't cover in class is good practice.)

"Will we still be doing all of our learning in the class, or will all of the learning be done at home? I only ask for people that aren't that good at learning from reading a textbook." (I would say half-and-half; the purpose of the flipped-class is to make sure that the time in class and at home is best spent for the specific type of learning you need.)

"What, in your opinion, is the most interesting part of astronomy?" (How stars are born, live, and die. Especially how stars die.)

"Do you believe astrology is able to make accurate predictions about your future?" (My horoscope said that you would ask that.)

"Flipped classes are not my favorite because I like to have a instructor on front of me." (Don't worry, I'll still be there in front of the class to clarify whichever concepts you're having problems with. Even if that's everything. As long as before class you provide me feedback on specifically what you had problems with.)

"Aren't you a some sort of secret side DJ?" (Yes, for Monday swing dancing at the Madonna Inn. Shh, it's a secret.)

20160822

Backwards faded scaffolding laboratory/presentation: limiting magnitude (Orion's Torso)

Astronomy 210L, spring semester 2011
Cuesta College, San Luis Obispo, CA

(This is the second Astronomy 210L laboratory at Cuesta College, San Luis Obispo, CA. This course is a one-semester, optional adjunct laboratory to the Astronomy 210 introductory astronomy lecture, taken primarily by students to satisfy their general education science transfer requirement.)

So where would you go in San Luis Obispo county to find the darkest skies available?

...and once you were there, let's say you were so impressed by the sheer number of stars that you wanted to count them all.

Maybe not--you might be able to look up the expected number of stars in a dark sky.

Or better yet, let's consider a systematic approach where you can count the number of stars on and within a certain part of the sky (the "Orion's Torso" asterism), and then be able to extrapolate this count to the total number of stars in the rest of the sky.

First, let's consider how to rate the brightness of a star. This is not the same thing as the "true" brightness of a star, just how bright a star is as it appears in the our sky. (So yes, our sun, a rather mediocre brightness star "cheats" because it happens to be very close, so that's why we talk about its "apparent" magnitude being bright in comparison to the rest of the stars that we can see from Earth.)

The original Greek scale has +1 for the brightest stars, and +6 for the dimmest stars. If the smaller number for brighter stars bothers you, think of ranking schemes (as did the Greeks), where the brightest stars were "first place" or "top tier" stars, and the dimmest stars are in "sixth place," earning the Miss Congeniality prize. And the scale did need to get revised, as there a few stars that blow the top off the original +1 to +6 scale. Brighter than the "first place" +1 stars are "zero place" stars, and brighter than those stars are "-1 place" stars. These are the hella bright stars--at least, for those astronomers who come from Northern California. There are also lots of stars dimmer than +6, but due to the limitation of the human eye these cannot be seen with the naked eye, even under the best of circumstances, but these stars can easily be observed with telescopes or even decent binoculars.


Streetlights cause light pollution. However, the other part of this effect is the atmosphere itself, as stuff in the air reflects the upward light back down towards our eyes, making it difficult to see the stars. And light pollution is not all manmade--the moon also does its damage as well.

So compare this view seen from a dark sky location (here seen through a telescope, so there are lots of stars much dimmer than +6 visible, as well as nebulae)...

...with the same part of the sky, seen with the skyglow of downwards reflected streetlight. The dim stars disappear, and even the brighter stars are harder to make out.

So instead of the naked eye being limited to seeing stars +6 and brighter, light pollution shifts the limiting magnitude to the left.

Let's now get to the process of counting stars within a representative, manageable portion of the sky, in order to extrapolate this to find the total stars in the rest of the sky.

Each group will pick up a packet of star charts showing Orion's Torso under dark, suburban, and urban conditions. Consider this training for actually doing this observation in the night sky.

You can't touch the stars with your fingers...no way, nuh-uh. So you need to stand at least 1 m back from the charts, and count these stars in your head, in order to simulate the approximate conditions for counting stars at night. Count stars on the border as well as inside Orion's Torso, compare results with your group members (you might even discover a "secret star" or two!), and determine the average number of stars within Orion's Torso for each light pollution condition.

The "Orion's Torso Stars, Ranked by Apparent Magnitude" table lists the stars from brightest to dimmest apparent magnitudes. If say, your group had counted an average of 22 stars under certain lighting conditions, then you look up the 22nd brightest star in Orion's Torso, and since it has an apparent magnitude of +4.93, this is the limiting magnitude for those lighting conditions--you can see all stars +4.93 and brighter, and can't see stars dimmer than +4.93.

Now use the "Number of Celestial Sphere Stars versus Limiting Magnitude" graph. With our example of a limiting magnitude of +4.93 in Orion's Torso, draw a line vertically upwards until you hit this diagonal, and then go horizontally and read off the corresponding number of stars in the entire celestial sphere under these lighting conditions. Here, approximately 1,600 stars.

But since this 1600 is the stars in the entire celestial sphere, and you can only see half of the celestial sphere above the horizon at any given time, then under these lighting conditions (22 stars in Orion's Torso, limiting magnitude +4.93), there would be expected to be only 1600/2 = 800 stars in the night sky.

After completing this laboratory, you should then be successfully trained star counters, and can find the limiting magnitude (and total number of visible stars in the sky) at various locations around San Luis Obispo county. Good times.

EQUIPMENT
Cuesta ThinkPad(TM) laptops (wireless networking, internet browser)
(appropriate, responsible in-class use of personal laptops allowed)
Orion's Torso light pollution star charts
"Orion's Torso Stars, Ranked by Apparent Magnitude" table
"Number of Celestial Sphere Stars versus Limiting Magnitude" graph
meter sticks (1 m)
rulers

CURRENT EVENTS QUIZ
(First 10 minutes of laboratory.)

BRIEFING
Limiting Magnitude (*.pdf) (*.mov)

BIG IDEA
Star brightnesses in the night sky are quantified by (apparent) magnitudes; man-made (and moon) light pollution limits the stars that can be seen with the naked eye.

GOAL
Students will conduct a series of inquiries about the magnitudes of stars using printed-out simulations of key asterisms, and be able to locate these asterisms using internet simulations and in the night sky for potential observations.

COMPUTER SETUP
Access the Heavens Above website for your campus by clicking on the appropriate link below, and then select "Astronomy > Sky Chart":
*Bowen Observatory, San Luis Obispo campus (*.html)
*Telescope shelter, North County campus (*.html)

You should now see a star chart for the current time/date, where north is at the top, and west is to the right.

TASKS
1. Exploration
"Orion's Torso" is not a true constellation, but an asterism made up of the brightest stars of the central part of the constellation Orion. You will determine when Orion's Torso will be highest overhead on the next available moon-less night. Then you will simulate counting the visible stars on and inside Orion's Torso, in order to determine the limiting magnitude, and the total number of visible stars in the sky.

a. Advance the time such that Orion's Torso is highest overhead tonight. If the sun and/or moon is visible anywhere in the sky, you will need to advance the date and adjust the time to find a moon-less date/time later this semester, within the next month or so when Orion's Torso is highest overhead at night. Record the following date/time below:

Available moon-less night within next month or so: __________.
Orion's Torso highest overhead time (to within +/- 10 min): __________.

b. Use a meter stick to space yourself at least 1.0 meter away from charts showing Orion's Torso under various conditions (dark sky, suburban sky, and urban sky). Count the number of stars visible on or within Orion's Torso (include the "corner stars"). Do this individually first, then determine the average result in your group for each viewing condition.

Dark sky average count: __________.
Suburban sky average count: __________.
Urban sky average count: __________.

c. Refer to the "Orion's Torso Stars, Ranked by Apparent Magnitude" table, which lists Orion's Torso stars, ranked from brightest to dimmest, along with the value of their apparent magnitude, denoted by m. List the names of Orion's Torso stars (if any) that are brighter than Polaris (the "North Star," a +2.00 magnitude star).

Stars brighter than Polaris in Orion's Torso (if any): __________.

d. The limiting magnitude corresponds to the dimmest star that can be seen under given viewing conditions. Using the "Orion's Torso Stars, Ranked by Apparent Magnitude" table, determine the average limiting magnitude value for your group for each viewing condition.

Dark sky limiting magnitude: __________.
Suburban sky limiting magnitude: __________.
Urban sky limiting magnitude: __________.

e. Refer to the "Number of Celestial Sphere Stars versus Limiting Magnitude" graph, which allows you to look up the total number N of visible stars in the entire celestial sphere, given a limiting magnitude from +1.00 to +6.00. (Divide N by two to get the number of visible stars in the sky, as it is only possible to see half of the entire celestial sphere at any given time.) From your limiting magnitudes in (d), use this graph to determine the total number of visible stars in the sky for each viewing condition.

Dark sky visible stars: __________.
Suburban sky visible stars: __________.
Urban sky visible stars: __________.

f. What generalization statements, in a complete sentences, can you make about (1) how the limiting magnitude changes with respect to light pollution; and (2) how the number of visible stars in the sky changes with respect to light pollution?

Generalization statements: __________.

Each person in your group should summarize their own Exploration answers, to be turned in today and selected randomly to be graded for their group(*).

2. Does Evidence Match a Given Conclusion?
Consider the following claim:
"In the center of a city, where the naked-eye limiting magnitude due to extreme amounts of light pollution can be [+4] or less, as few as 200 to 500 stars are visible [in the sky]."
--http://en.wikipedia.org/wiki/Naked_eye
Would you agree or disagree with this generalization based on the methods/evidence used in the previous task? Explain your reasoning and provide specific evidence from data to support your reasoning(*).

3. What Conclusions Can You Draw From This Evidence?
Due to campus streetlights, and from the neighboring Camp San Luis Obispo and the California Men's Colony, the Bowen Observatory on the roof of Building 2400 on the San Luis Obispo campus experiences a certain amount of light pollution.

What conclusions and generalizations can you make from data collected by Cuesta College Astronomy 210L students in spring 2006-2010 in terms of "Does the Bowen Observatory experience light pollution comparable to other suburban areas in San Luis Obispo county?"

Location:Orion's Torso stars:
Morro Bay27
South San Luis Obispo40
Creekside Farms, Paso Robles    21
San Miguel19
Santa Margarita35
Morro Bay23
Central San Luis Obispo19
Central San Luis Obispo17
Bishop's Peak30
Just off Cal Poly campus25
Cal Poly campus23
Templeton20
Bowen Observatory14, 13, 19, 17, 16, 17

Explain your reasoning and provide specific evidence to support your reasoning(*).

4. What Evidence Do You Need to Pursue?
Describe precisely what evidence you would need to collect in order to answer the research question of, "Is there more or less light pollution at the star party location on the North County campus (at the Telescope Shelter) than at the Bowen Observatory on the San Luis Obispo campus (Building 2400)?" You do not need to actually complete the steps in the procedure you are writing.

Create a detailed, step-by-step description of evidence that needs to be collected and a complete explanation of how this could be done--not just "Drive to each location and count stars," but exactly what would someone need to do, step-by-step, to accomplish this. You might include a table and sketches--the goal is to be precise and detailed enough that someone else could follow your procedure by simply checking off each step, without having to "interpret" the instructions(*). (Note: be sure to specify a moon-less date/time at least one week from today that these observations can be made.) Write up your procedure on whiteboards(*), to be worked on and presented as a group.

Reference:

Backwards faded scaffolding laboratory/presentation: limiting magnitude (Summer Triangle)

Astronomy 210L, fall semester 2013
Cuesta College, San Luis Obispo, CA

(This is the second Astronomy 210L laboratory at Cuesta College, San Luis Obispo, CA. This course is a one-semester, optional adjunct laboratory to the Astronomy 210 introductory astronomy lecture, taken primarily by students to satisfy their general education science transfer requirement.)

So where would you go in San Luis Obispo county to find the darkest skies available?

...and once you were there, let's say you were so impressed by the sheer number of stars that you wanted to count them all.

Maybe not--you might be able to look up the expected number of stars in a dark sky.

Or better yet, let's consider a systematic approach where you can count the number of stars on and within a certain part of the sky (the "Summer Triangle" asterism), and then be able to extrapolate this count to the total number of stars in the rest of the sky.

First, let's consider how to rate the brightness of a star. This is not the same thing as the "true" brightness of a star, just how bright a star is as it appears in the our sky. (So yes, our sun, a rather mediocre brightness star "cheats" because it happens to be very close, so that's why we talk about its "apparent" magnitude being bright in comparison to the rest of the stars that we can see from Earth.)

The original Greek scale has +1 for the brightest stars, and +6 for the dimmest stars. If the smaller number for brighter stars bothers you, think of ranking schemes (as did the Greeks), where the brightest stars were "first place" or "top tier" stars, and the dimmest stars are in "sixth place," earning the Miss Congeniality prize. And the scale did need to get revised, as there a few stars that blow the top off the original +1 to +6 scale. Brighter than the "first place" +1 stars are "zero place" stars, and brighter than those stars are "-1 place" stars. These are the hella bright stars--at least, for those astronomers who come from Northern California. There are also lots of stars dimmer than +6, but due to the limitation of the human eye these cannot be seen with the naked eye, even under the best of circumstances, but these stars can easily be observed with telescopes or even decent binoculars.


Streetlights cause light pollution. However, the other part of this effect is the atmosphere itself, as stuff in the air reflects the upward light back down towards our eyes, making it difficult to see the stars. And light pollution is not all manmade--the moon also does its damage as well.

So compare this view seen from a dark sky location...

...with the same part of the sky, seen with the skyglow of downwards reflected streetlight. The dim stars disappear, and even the brighter stars are harder to make out.

So instead of the naked eye being limited to seeing stars +6 and brighter, light pollution shifts the limiting magnitude to the left.

Let's now get to the process of counting stars within a representative, manageable portion of the sky, in order to extrapolate this to find the total stars in the rest of the sky.

Each group will pick up a packet of star charts showing Summer Triangle under dark, suburban, and urban conditions. Consider this training for actually doing this observation in the night sky.

You can't touch the stars with your fingers...no way, nuh-uh. So you need to stand at least 1 m back from the charts, and count these stars in your head, in order to simulate the approximate conditions for counting stars at night. Count stars on the border as well as inside the Summer Triangle, compare results with your group members (you might even discover a "secret star" or two!), and determine the average number of stars within the Summer Triangle for each light pollution condition.

The "Summer Triangle Stars, Ranked by Apparent Magnitude" table lists the stars from brightest to dimmest apparent magnitudes. If say, your group had counted an average of 27 stars under certain lighting conditions, then you look up the 27th brightest star in the Summer Triangle, and since it has an apparent magnitude of +4.93, this is the limiting magnitude for those lighting conditions--you can see all stars +4.93 and brighter, and can't see stars dimmer than +4.93.

Now use the "Number of Celestial Sphere Stars versus Limiting Magnitude" graph. With our example of a limiting magnitude of +4.93 in the Summer Triangle, draw a line vertically upwards until you hit this diagonal, and then go horizontally and read off the corresponding number of stars in the entire celestial sphere under these lighting conditions. Here, approximately 1,600 stars.

But since this 1600 is the stars in the entire celestial sphere, and you can only see half of the celestial sphere above the horizon at any given time, then under these lighting conditions (27 stars in the Summer Triangle, limiting magnitude +4.93), there would be expected to be only 1,600/2 = 800 stars in the night sky.

After completing this laboratory, you should then be successfully trained star counters, and can find the limiting magnitude (and total number of visible stars in the sky) at various locations around San Luis Obispo county. Good times.

EQUIPMENT
Cuesta ThinkPad(TM) laptops (wireless networking, internet browser)
(appropriate, responsible in-class use of personal laptops allowed)
Summer Triangle light pollution star charts
"Summer Triangle Stars, Ranked by Apparent Magnitude" table
"Number of Celestial Sphere Stars versus Limiting Magnitude" graph
meter sticks (1 m)
rulers

CURRENT EVENTS QUIZ
(First 10 minutes of laboratory.)

BRIEFING
Limiting Magnitude (*.pdf) (*.mov)

BIG IDEA
Star brightnesses in the night sky are quantified by (apparent) magnitudes; man-made (and moon) light pollution limits the stars that can be seen with the naked eye.

GOAL
Students will conduct a series of inquiries about the magnitudes of stars using printed-out simulations of key asterisms, and be able to locate these asterisms using internet simulations and in the night sky for potential observations.

COMPUTER SETUP
Access the Heavens Above website for your campus by clicking on the appropriate link below, and then select "Astronomy > Sky Chart":
*Bowen Observatory, San Luis Obispo campus (*.html)
*Telescope shelter, North County campus (*.html)

You should now see a star chart for the current time/date, where north is at the top, and west is to the right.

TASKS
1. Exploration
TThe "Summer Triangle" is not a true constellation, but an asterism made up of the three brightest stars (Altair, Deneb, and Vega) from the constellations Aquila, Cygnus, and Lyra. You will determine when the Summer Triangle will be highest overhead on the next available moon-less night. Then you will simulate counting the visible stars on and inside the Summer Triangle, in order to determine the limiting magnitude, and the total number of visible stars in the sky.

a. AAdvance the time such that the Summer Triangle is highest overhead tonight. If the sun and/or moon is visible anywhere in the sky, you will need to advance the date and adjust the time to find a moon-less date/time later this semester, within the next month or so when the Summer Triangle is highest overhead at night. Record the following date/time below:

Available moon-less night within next month or so: __________.
Summer Triangle highest overhead time (to within +/- 10 min): __________.

b. Use a meter stick to space yourself at least 1.0 meter away from charts showing the Summer Triangle under various conditions (dark sky, suburban sky, and urban sky). Count the number of stars visible on or within the Summer Triangle (include the "corner stars"). Do this individually first, then determine the average result in your group for each viewing condition.

Dark sky average count: __________.
Suburban sky average count: __________.
Urban sky average count: __________.

c. Refer to the "Summer Triangle Stars, Ranked by Apparent Magnitude" table, which lists Summer Triangle stars, ranked from brightest to dimmest, along with the value of their apparent magnitude, denoted by m. List the names of Summer Triangle stars (if any) that are brighter than Polaris (the "North Star," a +2.00 magnitude star).

Stars brighter than Polaris in the Summer Triangle (if any): __________.

d. The limiting magnitude corresponds to the dimmest star that can be seen under given viewing conditions. Using the "Summer Triangle Stars, Ranked by Apparent Magnitude" table, determine the average limiting magnitude value for your group for each viewing condition.

Dark sky limiting magnitude: __________.
Suburban sky limiting magnitude: __________.
Urban sky limiting magnitude: __________.

e. Refer to the "Number of Celestial Sphere Stars versus Limiting Magnitude" graph, which allows you to look up the total number N of visible stars in the entire celestial sphere, given a limiting magnitude from +1.00 to +6.00. (Divide N by two to get the number of visible stars in the sky, as it is only possible to see half of the entire celestial sphere at any given time.) From your limiting magnitudes in (d), use this graph to determine the total number of visible stars in the sky for each viewing condition.

Dark sky visible stars: __________.
Suburban sky visible stars: __________.
Urban sky visible stars: __________.

f. What generalization statements, in a complete sentences, can you make about (1) how the limiting magnitude changes with respect to light pollution; and (2) how the number of visible stars in the sky changes with respect to light pollution?

Generalization statements: __________.

Each person in your group should summarize their own Exploration answers, to be turned in today and selected randomly to be graded for their group(*).

2. Does Evidence Match a Given Conclusion?
Consider the following claim:
"In the center of a city, where the naked-eye limiting magnitude due to extreme amounts of light pollution can be [+4] or less, as few as 200 to 500 stars are visible [in the sky]."
--http://en.wikipedia.org/wiki/Naked_eye
Would you agree or disagree with this generalization based on the methods/evidence used in the previous task? Explain your reasoning and provide specific evidence from data to support your reasoning(*).

3. What Conclusions Can You Draw From This Evidence?
Due to campus streetlights, and from the neighboring Camp San Luis Obispo and the California Men's Colony, the Bowen Observatory on the roof of Building 2400 on the San Luis Obispo campus experiences a certain amount of light pollution.

What conclusions and generalizations can you make from data collected by Cuesta College Astronomy 210L students in spring 2006-2010 in terms of "Does the Bowen Observatory experience light pollution comparable to other suburban areas in San Luis Obispo county?"

Location:Summer Triangle stars:
Poly Canyon31, 31
Base of Bishop's Peak74
Tank Farm Road30
Avila Beach Road86
Templeton56
Los Osos40
Paso Robles61, 26, 79
Sand Spit Beach, Montaña del Oro    36
Highway 4176, 45
Bowen Observatory20, 48, 9, 18, 17, 10, 50, 12

Explain your reasoning and provide specific evidence to support your reasoning(*).

4. What Evidence Do You Need to Pursue?
Describe precisely what evidence you would need to collect in order to answer the research question of, "Is there more or less light pollution at the star party location on the North County campus (at the Telescope Shelter) than at the Bowen Observatory on the San Luis Obispo campus (Building 2400)?" You do not need to actually complete the steps in the procedure you are writing.

Create a detailed, step-by-step description of evidence that needs to be collected and a complete explanation of how this could be done--not just "Drive to each location and count stars," but exactly what would someone need to do, step-by-step, to accomplish this. You might include a table and sketches--the goal is to be precise and detailed enough that someone else could follow your procedure by simply checking off each step, without having to "interpret" the instructions(*). (Note: be sure to specify a moon-less date/time at least one week from today that these observations can be made.) Write up your procedure on whiteboards(*), to be worked on and presented as a group.

Reference: