Cuesta College :: Astronomy 210L :: Spring 2020

"Ever since we crawled out of that primordial slime, that's been our unifying cry, 'More light.' Sunlight. Torchlight. Candlelight. Neon, incandescent lights that banish the darkness from our caves to illuminate our roads, the insides of our refrigerators. Big floods for the night games at Soldiers Field. Little tiny flashlights for those books we read under the covers when we're supposed to be asleep. Light is more than watts and footcandles. Light is metaphor. Light is knowledge, light is life, light is light."
--Diane Frolov and Andrew Schneider, Northern Exposure,
Falahey/Austin Street Productions, (1993).

Equipment
Cuesta ThinkPad 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 (*.pdf)
"Number of Celestial Sphere Stars versus Limiting Magnitude" graph (*.pdf)
meter sticks (1 m)
rulers

Current Events Quiz
(First 10 minutes of laboratory.)

Briefing
Limiting Magnitude (*.blog)

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, set for your campus, by clicking on the appropriate link below, and then select "Astronomy > Interactive 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
(Record your lab partners' names on your worksheet.)
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.

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): __________.

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: __________.

Refer to the "Orion's Torso Stars, Ranked by Apparent Magnitude" table (*.pdf), 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): __________.

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 (*.pdf), 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: __________.

Refer to the "Number of Celestial Sphere Stars versus Limiting Magnitude" graph (*.pdf), 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: __________.

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], 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 Bay 27
South San Luis Obispo 40
Creekside Farms, Paso Robles 21
San Miguel 19
Santa Margarita 35
Morro Bay 23
Central San Luis Obispo 19
Central San Luis Obispo 17
Bishop's Peak 30
Just off Cal Poly campus 25
Cal Poly campus 23
Templeton 20
Bowen Observatory 14, 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(*).
(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.

Preparation/Reflection Points
1.0 = Pre-lab reading assignment
1.0 = Current events quiz
1.0 = Post-lab reflection assignment

Group Work Points(*)
Documentation (Tasks 1-3, graded from randomly selected group member)
2.0 = exploration complete and reasoning correct
1.5 = minor problem with exploration or reasoning
1.0 = minor problems with both exploration and reasoning
0.5 = problematic exploration and reasoning
2.0 = Poster/presentation (task 4)
(Graded for completion this week)

(Backwards Folded Scaffolding framework adapted from: Tim Slater, Stephanie Slater, Daniel J. Lyons, Engaging in Astronomical Inquiry, W.H. Freeman & Company, New York (2010).)