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Astr384 Class Projects, Spring 2008

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UPDATE August 2009: New shepherd's crook light fixtures have been installed around the commons lawn! A big thank you to the Calvin administration for the funds and to Physical Plant for the work involved with purchasing and installation. The view from the observatory deck is much improved - stop by when we're open to view the stars with us!


Proposal to Replace the Light Fixtures on the Commons Lawn

Astr 384 class: Kathy Hoogeboom, Jessie Taylor, John Vander Heide, Jess Vriesema, and Prof. Deborah Haarsma

Introduction

A clear night away from city lights can be an astounding thing. The light wash of the Milky Way, the full outline of the Little Dipper, meteors streaking across the sky, bright planets and millions of stars – maybe even a galaxy if you know where to look – are wondrous to behold, both exhilarating and humbling. Few sights can so easily show the vastness of the universe as those seen when we turn our gaze upward.

Maintaining and reclaiming dark skies is part of creating space for the appreciation of God’s creation. Furthermore, it is an important contribution to the astronomy education Calvin College can offer to both its students and its surrounding community.

Lighting on Calvin’s Campus

Current campus lighting of pathways and parking lots is accomplished primarily by three types of light fixtures: “china hat,” “cobra head” and “shepherd’s crook.” The former two types illustrate much that is problematic with older light fixtures installed without consideration for directional lighting.

Photograph of a "china hat" light fixture.

China Hat

Photograph of a "cobra head" light fixture.

Cobra Head

Photograph of a "shepherd's crook" light fixture.

Shepherd's Crook

The purpose of exterior light fixtures is to illuminate an area to help prevent crime and ease movement at night. To do this effectively, light must travel from the light source to an object (or person) to be illuminated, and bounce from there to an observer’s eye. Light that travels directly to the eye does not help one see anything – this represents a “waste” of light; worse, it can detract from a person’s night vision and hinder his or her sight of anything in dimmer light, just as when a driver or pedestrian is temporarily blinded by oncoming headlights and finds it more difficult to see for a time after the car has passed. This represents both a waste of the energy that produces the light which fails to usefully illuminate anything and a compromise to safety.

The Problem

The older campus light fixtures (cobra heads and china hats) fail by “wasting” light and making it harder for people’s eyes to adjust to different light levels as they walk around campus. Cobra head and china hat light fixtures send a great deal of light directly toward an observer’s eyes. The also send significant amounts of light up into the sky, where it is also “wasted” and contributes to overall light pollution.

Light spray pattern of

China Hat

Light spray pattern of

Cobra Head

Light spray pattern of a

Shepherd's Crook

In contrast, the shepherd’s crook light fixtures clearly send light downward rather than outward or upward (note the light cone of the shepherd's crook in image above). This puts light where it can illuminate rather than blind. Measurements of light levels show that the shepherd's crooks provide as much light at a distance of 10 meters as do the China hats, while providing more light near the posts.

While an ultimate goal will be the upgrade of all unshielded lighting fixtures on campus, some are more urgently needed than others. Here is where other goals – in particular, educational goals – can inform our priorities in accordance with Calvin’s Expanded Statement of Mission, which states, “In this community learning goes well beyond the classroom, making it possible and necessary that all campus life promote the educational tasks.” The light fixtures that most impact the educational mission of the observatory are the china hat style light fixtures on the Commons Lawn. Replacing the 23 china hat fixtures with shepherd's crook fixtures would be a total cost of $60,500, as estimated by Lucas DeVries from Calvin’s Physical Plant.

Astronomy Classes and Research

Light pollution greatly hinders the kind of research that can be done with Calvin’s telescope and the general familiarity with and appreciation of the night sky that its students can achieve. Part of the problem is our location in Grand Rapids, a city where general light pollution is a significant issue that Calvin cannot directly improve. But the china hat lights around the Commons Lawn present an additional, more direct and significant problem – a problem which can quickly be addressed by updating these lights to the shepherd’s crook style to match the Chapel patio lighting installed in 2007.

While some of these lights have buildings or trees between them and the observatory, a few of them shine directly at the observatory dome (marked with colored dots on this map). They are bright enough to cast clear shadows in the observatory

View of China Hat and Shepherd's Crook from Observatory deckThis photo (click to enlarge) was taken on the Observatory deck, looking south towards the chapel. On the right side of the photo is a china hat fixture, which is bright because light is shining directly toward the observatory. On the left side of the photo is a shepherd's crook fixture, which is almost impossible to see because it is NOT shining light toward the observatory. The pole, banner, and ground below the shepherd's crook are faintly visible.

Lights shining into the observatory are responsible for two types of damage. First, glancing in their direction can ruin one’s night vision, forcing the observer to wait several minutes before seeking faint objects or trying to identify constellations with dimmer stars. Second, they contribute to the overall sky glow, making it difficult to observe galaxies, nebulae or other faint objects, especially near the horizon.

These lights directly limit the ability of the observatory and the observers who work there to teach people about the night sky. Being able to see interesting objects in the sky is crucial for all astronomy classes as well as for those from the college and its community who visit the observatory.

Security

Maintaining a safe campus is obviously and rightly a major priority at Calvin and the main reason that we have so many exterior lights. These lights are designed to illuminate external areas to help prevent crime and ease movement at night. Both of these functions are necessary for the proper functioning of the campus, but they can be done more effectively than the current fixtures do.

Having an even distribution of light is beneficial because of how the human eye works. Our eyes are amazing light detectors that are able to function over a wide range of brightness levels. This is demonstrated by our ability to see both in full sun at noon and in the almost utter darkness of a moonless night. Still, the transition between those two light levels takes time, particularly when transitioning from bright light to dim light.

Uneven illumination from light fixtures on campus causes problems because out eyes are constantly adjusting as we move from one light level to another. The current china hat fixtures shine light directly into the eye. If a pedestrian then glances into a nearby shadowed area, the eye is not capable adjusting quickly enough to easily detect a person standing in the shadows.

The shepherd's crook fixtures have already been accepted as safe on the east side of campus where they are used in the parking lots and along the pathways around KE, the DeVos Communications Center and the Prince Conference Center,

Energy Usage

Lighting dark places requires a substantial amount of energy, especially when those dark places are as large as Calvin’s campus; the challenge is finding ways to light the campus as efficiently as possible.

Higher watt lights use more energy and often, but not always, produce more light as a consequence. Recently newer lamps have been developed that are able to produce more light using less power. The older china hat fixtures on Commons Lawn use 175-watt bulbs while the newer shepherd’s crook fixtures on the Chapel patio use only 150-watt bulbs. Moreover, the energy is used more effectively because more of the light shines on the sidewalk and pedestrians and less is wasted shining outward and upward. The replacement fixtures would use less energy, but provide

Grand Rapids Community

As a point of contact between the college and the Grand Rapids community, the observatory offers a perfect opportunity for light pollution issues to be easily communicated to others who may go out to affect their own communities. In this way, Calvin can indirectly improve the lighting conditions throughout the Grand Rapids by serving as leader and working model of such improvements. Dark skies require the cooperation of a whole community. A community as large as that of Grand Rapids will require a leader to follow if it is to change lighting to a more dark-sky friendly arrangement. Calvin College is well-poised to be such a leader by setting up an accessible, working system which others can learn from and imitate or improve.

Conclusion

The replacement of the china hat light fixtures around Commons Lawn with the newer shepherd's crook style lights will accomplish progress toward many of Calvin's goals. It will use energy more efficiently for lighting what needs illumination. It will improve the level of safety by allowing better vision in dim areas at night. It will further educational goals in the area of astronomy, as well as in general light pollution. It will help demonstrate to our community that light pollution can be reduced. And it will represent one more step toward reclaiming the dark sky that offers so much space for wonder at the magnificence of God’s creation.

 


Resources

Map indicating priorities

This map of part of Calvin's campus highlights which light fixtures we consider to be high-priority for replacement. Prof. Larry Molnar constructed the map, and writes:

"1) The highest priority are the three marked in red. From the dome, no building or tree blocks them in any way and they brightly illuminate our southern view (which is usually the most important direction as a consequence of how stars move).

2) The second highest priority are the two marked in green. Analogous to the red ones to the south, they directly illuminate our northern view.

3) The third priority is the one marked in cyan. After south, our eastern view is the most important. Most of the lights in this direction are at least partially obscured by trees. However, this one light is not, so it is prominent both from the dome and the observing deck."

Data

Light levels were measured around several campus light fixtures in spring 2008. Click here to download an Microsoft Excel 2003 document containing the data (also available in html). The graph below (click on it to enlarge) summarizes the results, comparing the light levels at various radii from the pole of the light fixture. The gray band marks the light level indoors in the Calvin's Crossing bridge.

graph of light distribution for various fixtures

 

Image Gallery

The following photos illustrate the light spray patterns of several fixtures on Calvin's campus. The photos were taken on a snowy, misty evening (February 4, 2008) when light scattered off the mist and illustrated the light distribution pattern of the fixture.

Thumbnail
Location
Light Fixture
Comments
Lower Knollcrest East parking lot

White: Shepherd's Crook

Orange: Cobra Head

The shepherd's crook fixtures have a clear downward light cone and illuminate the ground. Compare to the glaring orange from the more distant cobra head fixtures.
Science Building/Burton Street parking lot Cobra Head Notice the glare of light shining directly at the viewer.
Knollcrest East ice rink area Shepherd's Crook Notice how the light is directed downward.
Fine Arts Center parking lot Cobra Head  
Light near the Commons Lawn China Hat Notice the glare of light shining directly at the viewer.
Blue Safety Phone Other This blue safety light is meant to be easily seen at a distance rather than illuminate the ground, so the light is correctly directed at the viewer.
Sidewalk from Knollcrest East to Calvin's Crossing bridge Shepherd's Crook Notice how the light from each fixture is directed down, and how the sidewalk is fairly evenly illuminated.
(Same sidewalk from the bridge) Shepherd's Crook

When viewed from above, there is no light visible from the bulbs themselves. We mostly see the circles of light projected onto the ground where pedestrians walk. This shows that the light is being directed down.

Commons Lawn China Hat The light is shining directly at the viewer, and is much brighter than the ground it is supposed to be illuminating.
Looking towards Bolt-Heyns-Timmer from the observatory deck China Hat These lights cast shadows on the inside walls of our observatory dome.
Looking towards the Chapel from the observatory deck

China Hat (foreground, right)

Shepherd's Crook (background, left)

From the observatory deck, the difference in the fixtures is striking. Clearly, the china hat light shines light all the way to the observatory, but the shepherd's crook light keeps its light close by.
Looking towards the Chapel from between the Science Building and Hiemenga Hall

China Hat (foreground)

Shepherd's Crook (background)

The shepherd's crook light fixtures illuminate the banners in the background. Although the light posts are only slightly more distant than the china hat fixture in the foreground, they waste far less light by directing it down, where it is needed.
An older light on the wall of the Hekman Library Other Note the glare.
A newer light on the wall of the Hekman Library Other The shadow on the wall shows us that the light doesn't go towards the viewer, but illuminates the wall and the walkway below.
A light on the side of the DeVos Communication Center Other  
Walkway lights behind the Chapel Other Notice how these lights glare at the viewer.
Newer walkway light (and its lightcone!) near the Chapel Other This light isn't perfect, but it does keep its light below its source level.
Unshielded lights near DeVries Hall Other Although these lights resemble shepherd's crook fixtures, they lack the shield above the bulbs. This allows light to be lost as it spreads out in all directions.
Bunker Interpretive Center Other Isolated in the woods, the Bunker Interpretive Center casts almost no light at a distance, but still provides plenty of illumination in the entry way for safety's sake.