The colorful circles, squiggle, and lines of Stephen Antonakos’s sculpture hovering in the sky just north of Center City are still discernible. But the piece’s essence, its wow factor, is in its medium — neon — and that feature has long been gone.

Once a seemingly impromptu scribble in the dark sky, Neons for Buttonwood had its off-switch flipped more than a decade ago.

Now, though, the sculpture’s fans are working to bring it back. A committee of residents of CityView Condominium, on whose south tower the piece is perched, is seeking the money required for its restoration and relighting. About $100,000 has been raised toward a goal of $750,000, says Lynda Orfanelli, co-chair with Sonja Eveslage of the Relight the Sky Committee.

“I feel like it’s starting to happen,” said Orfanelli during a recent rooftop visit to see the sculpture, “but what we really need is that one big donor who has confidence in us, and that’ll give [other potential donors] a feeling like, ‘Yes, let’s get on this train.’”

Neons for Buttonwood sits atop a privately owned building, yet it is among Philadelphia’s most visible and recognizable pieces of public art. It may be little-remembered now, but in 1990, when the sculpture was first lit on what was then KormanSuites at Buttonwood Square, the city’s nighttime skyline was considerably less dazzling.

There was no coordinated effort to bathe building ensembles emerald when something was on the line for the Eagles or render them in cobalt or pink on other occasions.

“The reason we turned it off initially was because the Pope was coming to town [in 2015], and we had been spending a lot of money doing repairs,” said Orfanelli, “and it was only partially lit. So we decided to turn it off rather than embarrass the building.”

The sculpture remained off until last year, when it was discovered that while the smaller checkmark facing east could still illuminate, no other part would. The neon tubing was removed because parts of it were breaking off.

Planning a comeback for the 111-foot-long work required clearing a few hurdles.

The city’s Percent for Art program, which originally shepherded the sculpture, was contacted for approval since the restoration calls for using LED technology instead of the original neon.

The Greek American artist Antonakos — who died in 2013 and whose works are in the collections of major museums — was noted as a pioneering exponent of neon, and so Orfanelli and Eveslage paid a visit to his widow, Naomi Antonakos, in New York, for her blessing.

“Her reaction initially was, ‘My husband was a neon artist,’ and we said, ‘If he was alive today he’d probably be using LED,’” said Orfanelli. “And then she spoke to art consultants that she still deals with, and she got back to us and said, ‘OK.’”

The new LED won’t change colors as other building lighting elements in the city do, and will remain true to the original colors chosen by the artist.

As fundraising proceeds, leaders have a chance to piggyback onto another project. The repainting phase could happen while the building is putting up scaffolding for unrelated maintenance work expected next year — if the next $50,000-$100,000 can be found by then. Installation of the LED elements would happen when the rest of the money is raised.

It’s not lost on the committee that when Neons for Buttonwood is restored and relit, there will be one major group of Philadelphians who won’t be able to look out of their windows at night to see it: the building’s residents themselves.

“That was exactly our point in calling it ‘Relight the Sky,’” said Orfanelli, “because it’s for everybody else.”

For more information and to donate to the project: relightthesky.org.