COMET WATCHER BLAZED OWN TRAIL

Guided by her love of stars, onetime librarian Jean Mueller took an atypical path to astronomy, becoming a pioneering telescope operator and making significant discoveries

- CHARITY HUME

NANCY CHRISTIANSEN JEAN MUELLER, shown at the Palomar Observatory near San Diego in 1994, was the first female telescope operator there.

More times than she can remember, Jean Mueller stood on the catwalk of the Hale Telescope at the Palomar Observatory scanning the night sky, trying to time the exact moment to close the dome.

The Palomar Observatory, located an hour and a half northeast of downtown San Diego, is owned and operated by Caltech, and as telescope operator, Mueller was responsible for protecting its instruments from the weather. Inside the structure, a 200-inch mirror captured light from distant stars in a time window crucial to the observing astronomer’s research. But when a fog bank rolled closer, Mueller had to make the call.

"I would get the dome closed within a minute or two of the fog actually hitting it," Mueller said. "We are vigilant for anything that might damage the mirror. You don’t want acid rain on the mirror because that’s going to eat the aluminum coating. Ash, combined with humidity, can be caustic."

Mueller, a telescope operator at Palomar from 1985 to 2014, called her path to astronomy “nonstandard.” She had a graduate degree in library science and had worked as a librarian for USC for 10 years when she learned about a job opening at a different Southern California observatory: Mt. Wilson, run by the Carnegie Institution of Washington. The role: collecting data and operating the 60-inch telescope.