Acoustic Monitoring

Scientists have developed clever ways to study wildlife without disturbing them. One such method is called acoustic monitoring, which is used to estimate the population of amphibians, like frogs, in the wild. Instead of capturing or counting them one by one, researchers perform manual calling surveys (MCS). During these surveys, scientists listen for the calls of male frogs, which are most vocal during breeding season. By analyzing these calls, they can estimate the number of frogs in an area. But what does this have to do with astronomy?

Counting Frogs in Douglas County

In 2019, Dr. Doug Reagan, a renowned ecologist and naturalist, was conducting an MCS in a Douglas County Open Space Park near Larkspur. Since frogs are most vocal at night, these surveys are often conducted in the dark when the environment is quieter and the calls are easier to detect. While listening for frogs, Dr. Reagan happened to look up—and what he saw took his breath away. The night sky above him was stunningly dark, with countless stars twinkling overhead. Nestled in a valley, this park was naturally shielded from the bright lights of nearby cities like Colorado Springs, Castle Rock, and Denver. It was a perfect place, not just for counting frogs, but for observing the cosmos.

A Partnership is Born

Later that year, in August 2019, Dr. Reagan, Cliff Simpson, and a handful of members from the Denver Astronomical Society (DAS) were invited to visit the property, known as Sandstone Ranch. The goal was to explore the possibility of providing volunteers with telescopes for public stargazing events. The visit was a resounding success. DAS members marveled at the pristine night sky, and Douglas County representatives saw the potential for a new kind of outdoor education. A partnership was born. Through this collaboration, DAS gained access to a beautiful dark sky site for astronomical observation, while Douglas County could offer its residents a chance to connect with the night sky through educational events. By working together, both organizations could foster a greater appreciation for nature—both on Earth and beyond.

Sandstone Ranch Open Space

Sandstone Ranch is a breathtaking 2,038-acre open space in Douglas County, officially acquired by the county on December 27, 2017. With its stunning red rock formations, expansive hay meadows, and diverse wildlife habitat, it is considered the crown jewel of the county’s Open Space properties. The land also holds a rich ranching history, and its preservation ensures a careful balance between protecting its natural beauty and providing public access for recreation and education. Located just 40 miles south of Denver, Sandstone Ranch sits in the foothills of the Rampart Range, west of Larkspur. The property is bordered by Pike National Forest on one side and surrounded by ranches and open space, with very few nearby homes. This isolation makes it an excellent location for stargazing. The surrounding mountains help block much of the light pollution from Denver and Colorado Springs, allowing for spectacular views of the Milky Way and thousands of stars that are often washed out in brighter areas.

Sandstone Ranch Star Parties

The Denver Astronomical Society holds monthly star parties at Sandstone Ranch, offering visitors the chance to experience the wonders of the night sky in a truly dark location. Current events are temporarily held at an unoccupied house on the ranch’s property, which features a level concrete patio on two sides with excellent views of the northern, eastern, and southern horizons. The house itself provides modern amenities, including a full kitchen, seating, and two restrooms, offering a warm and comfortable retreat for attendees. Additional space is available on the surrounding lawn and around the building for those who do not require power for their equipment. During star parties, Open Space staff and DAS volunteers are on-site to facilitate entry and exit, ensuring a smooth and enjoyable experience for all attendees. These gatherings provide a fantastic opportunity for the public to engage with experienced astronomers, look through telescopes, and gain a deeper appreciation for the night sky in one of the best stargazing locations in the region.

More Than Just Stargazing

While Sandstone Ranch star parties are primarily about observing the night sky, they also serve as valuable educational opportunities. Many events feature special presentations and hands-on learning experiences for attendees of all experience levels. For example, the February 28, 2025, event featured Tommy Lease and Charlie Hagen from the DAS Astrophotography Special Interest Group (ASIG). They led a session on Astrophotography Assistance for Beginning and Intermediate Imagers, covering topics such as choosing photographic equipment, capturing celestial objects, and processing images to enhance data quality. Meanwhile, visual astronomers took advantage of the dark skies to work their way through the Messier catalog, viewing stunning targets like M42 (the Orion Nebula), M44 (the Beehive Cluster), M48, M67, and M81 (Bode’s Galaxy).

Looking Toward the Future

Future stargazing events will be moved to their permanent location at another house on the ranch that is under preparation with the same amenities as the current house. Future projects for Sandstone Ranch between Douglas County Open Space and volunteers from the DAS  include building an observatory that will house three telescopes; six cement pads with power for additional telescopes will be placed near the observatory; and a multi-use amphitheater will be constructed near the building that will serve as a warming facility and classroom. Additionally. the DAS aims to hold more frequent star parties at Sandstone Ranch, but of course, this is dependent on assembling a staff of volunteers, training official Open Space Guides, and coordinating with Douglas County, who ultimately sets the number of visitors and the frequency of events held in the park. Please check out our volunteer page you’re interested in helping out at Sandstone Ranch. DAS Members can also find out more information in the #Sandstone channel in Slack.

Keep Your Eyes Open

Dr. Doug Reagan may have been counting frogs that night in 2019, but by simply looking up, he discovered something extraordinary—an amazing dark sky in Douglas County. In the same way, astronomers look up and find breathtaking celestial wonders, from distant galaxies to glowing nebulae. Whether you’re scanning the night sky or just enjoying the natural beauty around you, there’s always something to discover if you keep your eyes open. The Denver Astronomical Society continues to host regular events at Sandstone Ranch, offering unique opportunities to experience this incredible dark sky site. If you’re interested in joining a future star party, keep an eye on your email inbox for announcements and invitations. You never know what amazing sights await at Sandstone Ranch.