Designing for Darkness: Combating Stray Light at the 46 North Astronomy Center

Building a community astronomy center is an exciting endeavor, and as the team behind the 46 North Astronomy Center in Wisconsin's northwoods gears up, they're facing a critical design hurdle: minimizing the impact of stray light.

The 46 North Astronomy Center is set to feature an observatory with a substantial 20-inch telescope, an observing lawn for public stargazing, and a community education building that will also house administrative space, storage, and potentially dormitories.

A significant part of ensuring optimal viewing conditions involves carefully planning the landscaping to shield the observatory and observing lawn from artificial light sources, particularly vehicle headlights. The team is considering two main approaches:

Option 1: The Protective Berm

This design involves constructing a berm to separate the parking lot from the observatory and observing lawn. The idea is that the elevated earthwork will physically block the direct line of sight from vehicle headlights to the sensitive viewing areas.

Option 2: The Raised Plateau

Alternatively, the plan could involve creating a flat, raised plateau. This would position the observing lawn and observatory approximately 15-20 feet higher than the parking area, effectively creating a natural barrier against headlights from cars, trucks, ATVs, UTVs, and snowmobiles entering the facility. The main access road is also being designed with curves to help mitigate light spill.

Considerations from the Community:

When this design question was posed to the wider astronomy community, valuable insights emerged. One suggestion pointed to the recent renovations at Cherry Springs State Park in Pennsylvania, which incorporated berms to block nearby roadways. This approach was found to be highly effective, although it was noted that in conditions of fog or high humidity, headlights could still refract through the moisture, appearing as visible light over the berms. However, in such conditions, astronomical viewing is often already compromised, making this a less significant issue.

Another crucial consideration highlighted is the placement of doors for all buildings. These need to be strategically positioned so that when opened, interior lights do not spill out and illuminate the observing field, especially during activities like quick trips to the restroom or warming up inside during colder months. This is vital for events like star parties where telescopes are set up on the lawn.

The Path Forward

While the plateau option hasn't been as widely documented in practice, the consensus leans towards the effectiveness of physical barriers. The 46 North Astronomy Center team has a significant decision to make that will directly impact the quality of their stargazing experience. We'll be following their progress with great interest!

(Image placeholder: Imagine a graphic illustrating the two landscape design options with arrows indicating light paths.)