Night Sky Initiatives

Steaming geysers spray skyward to the starry night at Yellowstone National Park, Wyoming.
Steaming geysers spray skyward to the Milky Way and starry night at Yellowstone National Park, Wyoming.

Neal Herbert / NPS

NPS landscape architect Lynn Chan stands beside and looks up at the lamp post fixture.
NPS landscape architect Lynn Chan looks up at a light fixture that she helped design to improve outdoor lighting and reduce light pollution in Yellowstone National Park, Wyoming.


Yellowstone National Park: Q&A with Lynn Chan, landscape architect

Yellowstone National Park was often referred to as “Wonderland” by early visitors, and with good reason. Spanning three states and encompassing more than 2.2 million acres in the center of the Greater Yellowstone Ecosystem, the park is rich with features that are a wonder to behold. Its colorful hot springs, steaming geysers, thundering waterfalls, and diverse wildlife, including many large mammal species, are among the attractions that have drawn visitors there since its establishment as “the first national park” in 1872. And at night, glittering above this remote landscape is the star-filled sky—a vast wonderland of its own.

Nighttime views and environments are among the important resources the National Park Service protects. Since the early 1990s, Yellowstone has taken a leadership role in preserving its nighttime setting by making outdoor lighting improvements across the park. Landscape architect and park employee Lynn Chan has led many of these initiatives. Chan discussed the work of her team with NPS communications specialist Julie West of the Natural Sounds and Night Skies Division (NSNSD). The division provides expertise for measuring light pollution, reducing its effects, and raising awareness about the importance of the night sky resource.

Winter, snowy view to the yellow exterior of the Lake Hotel with a fully shielded replica of a historic light in the foreground
Winter view to Lake Hotel shows a fully shielded light fixture, a replica of the historic lighting design in Yellowstone National Park circa early 1900s.



Julie: How does a naturally dark night sky contribute to the “wonderland” character of Yellowstone National Park? Why is this important?

Lynn: The majority of Yellowstone is recommended wilderness. With more than four-million people a year, tourism mostly takes place along the road corridors and in developed areas. The rest of the park is still very much a wilderness setting. That setting at night is an important resource that we want to keep dark, not just for our own experiences but also for the natural elements such as wildlife and plants that need a normal day and night cycle to survive and thrive. Yellowstone is a hub in a large, remote natural resource area surrounded by U.S. Forest service and Bureau of Land Management land and connected to Grand Teton National Park. We have a great opportunity to set an example for preservation of the dark night sky in the Greater Yellowstone Area. Yellowstone is a special and unique place, and we want to preserve that remoteness and vastness at night as well as by day.

Julie: Take me back in time to Yellowstone’s early years and the original park lighting.

Lynn: The first electric power in the park was generated in Mammoth Hot Springs in 1903. Lights were then added around the parade ground at Fort Yellowstone. When lighting started to become common, there was not much thought for the importance of the dark beyond the area being lit, and little understanding of the importance of good lighting design, either for safety or minimizing light pollution. The 100 years of lighting that followed added sporadic lighting, most of which added to the park’s light pollution.

Today we’re trying to improve much of our existing outdoor lighting. We’re shielding lights to be respectful of the wilderness beyond while installing light fixtures that create a safe night-time setting for employees and visitors within developed areas. Our lights are fully shielded, which means not only no upward light but also no sideways light. Color spectrum is another consideration. In those early days, the park had incandescent lighting that cast a warm white light. We think it is important to maintain that historic ambience. Although more efficient, modern, blue-white light is harsh and refracts into the atmosphere, which creates light pollution. It adversely affects wildlife and visitors. At the same time, the least impactful form of light, in the amber or yellow spectrum, looks industrial and doesn’t fit the historic park setting, either. So what we want is that early, incandescent, warm-white color.

Lighting Improvement Strategies

Julie: What were the goals driving lighting improvements?

Lynn: We started improvements in the early ’90s, and made sure that any lighting retrofits or improvements were fully shielded, recognizing that developed areas in Yellowstone are small and surrounded by darkness. We got a good start by working with General Electric (GE) through our non-profit organization. GE had a lighting engineer who helped us understand the importance of taking light readings, checking lumen and foot-candle levels, and making sure areas weren’t over-lit and were properly designed to accomplish consistent, low-light levels. At the time, the big push from the International Dark-Sky Association was to prevent upward light from going into the sky. We wanted to take it one step further and say that we didn’t want sideways light, either.

In order to get fully shielded, low-level lighting appropriate to our historic districts, we had to design and build our own lights. We were fortunate to have a great metalsmith and chief electrician. I designed many lights based on historic styles because there weren’t any available in the commercial lighting industry. We built three or four different, early designs. We think we built the first lantern style fixtures that you see now with LED bulbs in the top and no glass in the sides. We looked for those 20 years ago, but nobody was making them. One of our lights was nicknamed the cow bell—a simple, iron hat with a bulb inside. Then we made a lantern that was similar to the historic lanterns at Old Faithful Inn but with no glass in the sides. People said it looked unfinished and needed glass, but we knew that glass acts like a lens and creates light pollution. We stuck to our guns. Once people got used to them, they thought they were cool. Now everyone is making fully shielded historic-looking lights; the industry has gradually changed to meet that need.

Photo compares un-shielded and shielded lights at Mammoth Hot Springs, Yellowstone NP.
Photo compares un-shielded (left) with shielded (right) light fixtures at Mammoth Hot Springs, Yellowstone National Park.


Fully shielded light fixture directs light down over a cabin door.
A fully shielded light directs lights down over a cabin door at Yellowstone National Park.


Julie: Surely the learning curve was fairly steep. What did you do to educate yourself? Walk me through your process of initiating a plan and getting others on board.

Lynn: We were a team right from the beginning. As a landscape architect, I had the skills to design the lights and the lighting plans. My supervisor was supportive and keen that we take the lead. We worked closely with our electric shop and other park staff to make sure that everybody knew what we were doing, what our goals were, and the science behind it.

We purchased a light meter and did retrofits in test areas. We went out at night and took readings of the foot-candles on the ground. Full moon light was our standard for the least level of light in a lit area. We used 2 foot-candles as the standard for the highest level of light under the fixture itself, and 0.02 at the furthest edge of the lit area (the same as full moon light). We used GE computer software that would tell you the foot-candles on the ground at a certain pole height, so you’d know how far apart your lights needed to be if you wanted a certain level of continual light. We learned how to do lighting design based on those parameters. We still use those parameters today. Of course, there have been many changes in the industry since then, and LEDs have become mainstream for outdoor lighting. LEDs changed everything—size, wattage, energy conservation, color opportunities, and controls.

Julie: That’s good to hear that the lights that you installed back then and those standards are still effective and holding. Some parks use alternative lighting like glow-in-the-dark paint, step lights, and sensors. Is Yellowstone exploring these alternatives?

Lynn: We tackle things on a case-by-case basis. We have snow in winter, so lights on steps or the ground don’t work very well for us. If you put step lights in, they will shine out into the night. Our aim is to create lighting that always points down. If you want to light steps and there is a bannister, then put shielded lights under the bannister and space them so they can light the treads without shining out. We’ve done yellow paint in some places, but we don’t do that a lot because it tends to wear off with heavy foot traffic and doesn’t look great in historic or natural settings. Sensors are very useful. One of our goals is energy conservation. Every retrofit and upgrade we carry out, we do not only for the night sky but for energy conservation. With sensors, you are making sure lights are off when not needed, thereby saving energy.

Julie: Have visitors been receptive to these improvements? Or have they expressed concerns for safety?

Lynn: Visitors have been very positive. I think people appreciate coming into an area and seeing that we’re making an effort to keep light low. We get compliments when we’ve done it right. I actually get more letters about the improvements, and complaints about the over-lit areas or lighting we haven’t improved than people complaining about too little light. It’s more the employees who have told us where we need light, and we have always worked with them to create the right level of lighting that we feel creates a safe setting. We go through it case by case. We look at the need and decide as a team what is needed. For example, does this path need to be fully lit? Are the people walking it more concerned about needing to know where the path is than about animals jumping out (which is unlikely)?

In Yellowstone our developed areas are like villages. We recognize the need to create a safe setting by lighting areas where people have to go after dark. But once you step beyond a building, parking area, or porch light, often you’re in complete darkness and approaching that wilderness setting. We work to make sure lights are low level, consistent, and don’t create bright spots surrounded by darkness in the middle of nowhere. To this end we have learned a lot about transition zones, e.g. making sure that a porch light is dimmer than a hall light, and if there are parking area lights beyond a porch light, then those levels should be dimmer in order for the eyes to adjust.

In areas where we don’t need to light the whole pathway, we use post-mounted bollard lights as wayfinding aids. A light on a small, 3-foot post is not going to spread much light if it’s fully shielded. In a developed area where there is a high need for lighting where people exit buildings, we make sure the lumen levels that we’ve set forth are met, and that the area is continually lit so you don’t go from light to dark and light to dark again. We may decide to light an entire parking area if a building is used after dark, but we won’t light beyond that. Our standards specify no lighting in the backcountry. You will not see any permanent outdoor lights on backcountry cabins or at road junctions.

Shielding is installed on typical par spot lights on a building
Shielding is installed on typical par spot lights on a building at Yellowstone National Park.


Putting Plans Into Action

Julie: You spoke about improvement strategies. Are there specific areas in Yellowstone where you are concentrating your efforts? How do you decide where to start?

Lynn: That’s a great question. In the past we focused on improving safety and old lights that caused glare issues. Recently we’ve been working with Bryan Boulanger, an engineer and professor at Ohio Northern University, to do an entire inventory of outdoor lighting in the park. That is one of the things needed before you can apply to be a “Dark Sky Park” with the International Dark-Sky Association. We have over 5,000 outdoor lights in Yellowstone, so it’s a huge job. I had wanted to do an inventory for years. Using a phone app he developed, Bryan took photos and “GPS’ed” every light in the park. Now we have a list with each light pinpointed on a map. This is a huge help for developing a lighting strategy. You can click on the map and see what light is where. Bryan is also starting to help other parks and hoping they can use his app for collecting data.

Bryan and I divided lights into categories to figure out how bad or good they are, e.g., “shielded, too bright,” or “not shielded, too bright,” or “compatible in all ways” (shielded, not too bright, and in the right color spectrum). To become a Dark Sky Park, a park is required to get to 67 percent compliance with fully shielded lights at the right lumen level and color spectrum within 3 years of their application. What I would like to do is to start with the lights that are the worst—too bright, too high, and not shielded. We can then take this information to park management, our electrical shop, and concessioners and say, “OK, we have this list. Can we support a strategy each year to improve?”

Julie: You were implementing lighting changes before the Natural Sounds and Night Skies Division was even formed. Have you worked with members of our team to realize your goals?

Lynn: In the early days, we engaged with the NPS dark sky team, which at that time consisted of employees Chad Moore and Dan Duriscoe. They were taking night sky inventories in parks and did some photography for us that showed light pollution levels. I also had contact with NPS headquarters in Washington and our Intermountain Region office. Recently I’ve worked with Frank Turina [NSNSD Policy Planning and Compliance Manager], and Karen Treviño [NSNSD Division Chief] from your team. Their focus is more on night sky science, and understanding why proper lighting is appropriate and important. Frank explains the types of effects that lighting has on the atmosphere, wildlife, and human health, and I am able to follow that with solutions, i.e., how to fix existing lighting issues and design new lighting. The two approaches work well together, and I would love to do more collaboration.

 Bison proof, rustic bollard lights are installed on an employee pathway at Yellowstone NP.
Bison proof, rustic bollard lights are installed on an employee pathway at Yellowstone NP.


Julie: How have these improvements made a difference, and to what or whom?

Lynn: There is more and more evidence that artificial lighting impacts wildlife and human health. Science has shown that we need to be in the warm-white or amber spectrum. Basically, don’t create daylight when it’s supposed to be night. We want to stay away from higher Kelvin (K) color ranges that replicate daylight. [Kelvin refers to the color temperature of lights. Home fixtures typically have color temperatures of 2700K, compared to industrial-commercial lighting, which can be higher than 3500K.] If we need light at night, then we should be in a color spectrum that supports our circadian rhythms and doesn’t have a negative impact.

Being a big wildlife park, Yellowstone wants to be a leader in preserving and protecting that resource, both in the day and the night. We pay attention to the science because it is important for wildlife, birds, insects, and all of Yellowstone. More and more, people recognize the importance of having a dark sky setting, and that you can also create a safe environment with less light. They don’t want to be annoyed by glaring lights and light pollution that we all used to take for granted.

Julie: In what ways does the park raise awareness around night sky issues?

Lynn: Yellowstone has an opportunity to educate people through what we do. We want to show that it’s possible to do things better. Yellowstone is a great place for stargazing. Our resource education division has made an ongoing effort to host stargazing sessions involving local universities. There is a very active astronomers association in Bozeman, Montana, which is the closest university town to our headquarters. Bozeman has been progressive in putting forward standards for dark sky and outdoor lighting. And the town of Livingston, MT is starting to do the same.

Night sky programming and education are things we would like to do better going forward. And I would love to do more with our gateway communities, which are much smaller towns. I hope Yellowstone’s effort to become a Dark Sky Park will give us an opportunity to say, “Hey, Yellowstone is trying to do this. Could we help you do something in your town?” Implementing change can be difficult, but there’s enthusiasm to do better. Working with other parks is also something we do. Glacier National Park took our design for bollard lights, which look rustic and won’t get knocked down by large wildlife rubbing up against them. I sent that design to several other parks.

A sky guard replaces the lens on a typical yard light to make it fully shielded
LED lighting combined with fully shielded fixtures save energy and reduce light pollution.


Practical Benefits

Julie: What about energy efficiency and cost savings?

Lynn: Energy efficiency is probably as big if not bigger a driver of these improvements as light pollution. With the age of LEDs, it makes so much more economic sense to upgrade lights, as energy use can be cut by half or more. Any time we do a lighting retrofit, we run energy comparisons. It’s simple math. For example, there are X number of lights burning X many watts that are on X amount of the time, which equals X amount of cost to us. We know what our electric power bill is per kilowatt hour, so it’s easy to calculate the savings fairly accurately. Lighting improvements typically pay back within a year.

Early LEDs were cheaply made diodes mostly in the blue light spectrum, and they didn’t last as long as they were supposed to. Now you can get quality LEDs in almost any color that are very reliable and last a long time. The cost has come down considerably, and, most importantly, they are getting more and more energy efficient. Every park should be retrofitting with LEDs, and there’s an LED for everything, indoor and outdoor. Another benefit is that recycling is much easier. That had been a big downside with fluorescents and compact fluorescents, which had mercury in them, as did many of the vapor type lights. LEDs are a totally different technology. It’s like having a computer chip more than a bulb.

Julie: What makes you most proud about the role you’ve played in addressing lighting improvements in Yellowstone?

Lynn: Things like this interview make me feel there is growing interest and understanding, and also when people approach me and ask to hear what we have done and to share information. My biggest goal is to get everybody on board so that those involved in lighting understand and carry out best practices. Lighting is an impact on natural resources that is easy to change if we have the resources to do it. I don’t want to imply that we’ve met our goals. We are nowhere near where we would like to be. This is a huge park. But I do think there is a lot more recognition now from our staff and managers of what good lighting needs to be. We’ve done some great projects in Yellowstone, and I think we’ve learned a lot and continue to learn how to do things better.

Julie: That’s great! Thank you, Lynn, for taking the time to speak with me.

Lynn: Thank you! I am really enthusiastic about this topic. I also can’t speak highly enough of the work that Bryan has done to support Yellowstone’s effort to become a Dark Sky Park. I hope to bring more people in along the way.

Article by Julie West, Communications Specialist, National Park Service Natural Sounds and Night Skies Division.

Photo shows the glow of wasted, excess light from an un-shielded light (as bright as the moon), compared to a shielded light.
Photo shows wasted, excess light from an unshielded light glowing as bright as the moon, left, compared to a shielded light, right.