JUST AFTER 6 o'clock on Monday night, about a dozen people were scattered around the meeting room at the Chestnut Hill Friends Meetinghouse, laying on their backs, staring at the ceiling.

They stretched out on yoga mats and padded benches in the minimalist, white-walled room, waiting for sunset. The retractable roof opened, exposing the meetinghouse to the elements and providing its inhabitants an unobstructed view of the sky.

Then the lights began, multicolored hues that circled the opening in the vaulted ceiling as part of an art installation titled "Greet the Light," which artist James Turrell calls a "skyspace."

During a captivating 50-minute show, deep hues of amethyst, emerald and turquoise faded into each other through the skylight - like watching colors on film, with only the occasional bird flying overhead to remind viewers that it's actually the sky. Organizers say no two shows are the same.

Stuart Shils, a painter who grew up in Mount Airy, said he was captivated by the way the artist made something extraordinary out of what seems so simple.

"With paintings, canvasses are filled with pigment, but there's no pigment here," Shils said after sundown, his eyes flickering with excitement. "It's a viewfinder to nothing, yet that ceiling is extremely active. What's going on between the two of them [the sky and ceiling] is beyond any painting I've seen. It's more like cinema."

Since the permanent installation opened this week in the new meetinghouse, on Mermaid Lane just off Germantown Avenue, the skyspace has been open to the public at dawn and dusk. The viewings will be held twice daily through Saturday. After that, the installation will be open at sunset Tuesdays and Sundays, and an hour before sunrise on Tuesdays and Thursdays, weather permitting.

Turrell worked with local architect James Bradberry to plan and design the installation at the meetinghouse, which opened last month. Some of Turrell's work was recently exhibited at the Guggenheim Museum in New York.

The weeklong special skyspace showings also drew two Temple University students working on their master's degrees in architecture. Student Mike Carwile, 24, said he couldn't have anticipated what it would look like.

"It just came over me," Carwile said.

Shils, the painter, said the skyspace inspired him and his work.

"It rips you off the floor. You're levitated," Shils said. "He's creating something here that's total extraordinary magic. We're in the presence of a great magician."