Light Pollution Lab February Version
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School
University of California, San Diego *
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Course
107
Subject
Astronomy
Date
Apr 3, 2024
Type
Pages
8
Uploaded by AgentYak3506
Light Pollution Lab Name _____________________ Introduction
In this lab you will directly investigate the effects of light pollution in your neighborhood in three steps. •
Part 1: You will read important information about light pollution and take a brief quiz on Canvas. •
Part 2: You will choose a location within your community, observe which types of outdoor lighting are used, and assess their impact. •
Part 3: You will make observations at night to determine the overall darkness of the sky. Part 1: Light Pollution Basics
Please read the materials and watch the videos posted on canvas, then complete the Light Pollution Basics quiz online. Part 2: Neighborhood Lighting Assessment This portion of the lab should be completed outdoors at night, ideally in your neighborhood. However, you could also do this at your workplace or somewhere else that you feel safe at night. Only if it is safe, take a walk around the area after it is dark. It is highly recommended that you bring a friend or relative with you; do not walk around alone at night anywhere that you feel unsafe. Make sure to respect your neighbors’ privacy, and do not take any photographs into their windows. •
You will need to bring several things with you: o
This document o
Clipboard and paper or notebook for taking notes on what you observe o
Pen or pencil o
Smartphone or camera + flashlight Observing Glare 1.
Try to look up at the stars. How much does glare (direct light shining in your eyes) affect your experience in this neighborhood? Do you find that you need to move around to find spots that aren’t in direct light, or is there very little glare?
Observing Light Trespass 2.
If you’re at your hom
e or workplace, look all around the building. Is there any light trespass that your residence or workplace is causing onto other properties? 3.
If you’re at your home or workplace, look all around the building. Is there any light trespass that other lights are causing onto your residence or workplace? If so, describe it. Observing Lighting Fixtures 4.
What type of street lights are used in the area? Describe the color and brightness of the street lights. Are they shielded or unshielded? (If the street lights are too bright to tell the shape of the fixture, you may need to return in the daytime.) 5.
What other types of outdoor lighting are used on or around buildings? Are these lights shielded or unshielded?
Photographs Take 5 photographs of outdoor lighting. You will upload these to Canvas. Evaluating Outdoor Lighting 6.
For each light that you photographed, decide which example light from the next page it matches most closely, then state wither this is an unacceptable/discouraged light fixture or an acceptable light fixture. 7.
Overall, do you think this neighborhood does a good job or a poor job at limiting light pollution? Explain your reasoning and justify your answer. Light fixture Which type in the examples picture does it best match? Is it unacceptable/discouraged or acceptable? Photo 1 Photo 2 Photo 3 Photo 4 Photo 5
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Part 3: Sky Darkness Assessment If possible, you should complete this assignment on a night when the moon is not visible. During this portion of the lab, you will observe the sky in order to estimate the limiting magnitude
of the sky. Limiting magnitude is a number that identifies the faintest stars that can be seen. The higher the number, the fainter the stars that can be seen and the better the sky quality. Skies that are very light-polluted have low limiting magnitudes, meaning that only very bright stars can be seen. Please watch the video instructions on Canvas before attempting this portion of the lab. The video will show you how to locate the constellations Ursa Minor and XXXXXXX. Instructions: Find a spot where there is no direct light causing unwanted glare. If you are at home and have outdoor lights, be sure they are all turned off. Wait outside for at least 5 minutes for your eyes to adjust to the darkness. 1.
Locate the constellation Ursa Minor in the sky. Using the Ursa Minor Limiting Magnitude Guide, decide which rough estimate of limiting magnitude best matches what you see (circle one): Limiting Magnitude:
2 or worse 3 4 5 or better 2.
Locate the constellation Leo in the sky. Using the Leo Limiting Magnitude Guide, count how many stars you can see in the area of the sky represented by the shaded trapezoid, including the stars that make up its corners if they are visible. How many stars do you count? _________________________ 3.
Use the table below to find the limiting magnitude of the sky based on your answer to the previous question. What is the limiting magnitude of the sky based on your observation of Leo? _____________________________ Limiting magnitude table adapted from http://nineplanets.org Number of stars seen in trapezoid region of Leo Limiting Magnitude 0 worse than 1.3 1 1.3 2 2.2 3-4 2.6 5 3.4 6 3.8 7 4.4 8 5.0 9-11 5.6 12-13 5.7 14-15 6.0 16-18 6.1 19-20 6.3 21 6.4 22+ 6.5 or better
4.
Are your two estimates of limiting magnitude (from observing Leo and from observing Ursa Minor) consistent with one another? If not, explain why you think they don’t match. 5.
The classes below have been adapted from the Bortle Dark Sky Scale. Based on your estimate of limiting magnitude
, which class best matches the sky’s quality at your location? Does the description of the class you chose match with what you observed? Explain. Class Limiting Magnitude Description Class 1: Excellent dark sky site 7.6 - 8.0 Objects on the ground are almost completely invisible. Many galaxies and very faint deep sky objects are visible to the naked eye. Class 2: Typical truly dark site 7.1 - 7.5 Much of the structure of the Milky Way is visible. Clouds appear as “dark holes or voids in the starry background.”
Class 3: Rural sky 6.6 - 7.0 Some evidence of light pollution visible along the horizon. Objects on the ground are faintly visible to a distance of 20 - 30 feet. Class 4: Rural / suburban transition 6.1 - 6.5 Light pollution is obviously visible from towns or cities in several directions. Milky Way is clearly visible but does not appear to have well-defined structure. Clouds near light pollutions Class 5: Suburban sky 5.6 - 6.0 The Milky Way may be invisible near the horizon, and it may appear weak or washed-out. Clouds in most directions appear brighter than the sky itself. Class 6: Bright suburban sky 5.1 - 5.5 The Milky Way is only visible directly overhead. There is enough light to easily see objects on the ground once your eyes adjust to the darkness. Clouds appear fairly bright. Class 7: Suburban/urban transition 4.6 - 5.0 The Milky Way is almost or completely invisible. The whole sky has a vague grayish-white color. Light pollution sources are evident in every direction. Class 8: City sky 4.1 - 4.5 The sky appears whitish-gray or orange. It is possible to read newspaper headlines without any trouble. Familiar constellations are difficult to make out, or parts of them are invisible. Class 9: Inner-city sky Less than 4.0 The entire sky is brightly lit, even straight overhead. Many parts of familiar constellations are invisible, and dim constellations may be missing from the sky entirely.
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Ursa Minor Limiting Magnitude Guide Ursa Minor with the apparent magnitudes of key stars displayed. Ursa Minor in a sky with Limiting Magnitude = 5 Ursa Minor in a sky with Limiting Magnitude = 4 Ursa Minor in a sky with Limiting Magnitude = 3 Ursa Minor in a sky with Limiting Magnitude = 2
Leo Limiting Magnitude Guide
When you’re outside at night, see if you can find the shape of Leo. If you live an extremely light polluted area, such as the center of Los Angeles, you may only be able to see one or two of the brightest stars, but most people live in places where they can see at least some additional stars in Leo. Count up how many stars you can see in the shaded region, including the four stars on the corners of the shaded area if they are visible. If you can’t see them at all, then you can say that there were zero stars in the shaded region.