On the night of July 22, 1995, the stars aligned for Thomas Bopp. A 47-year-old parts manager living in Glendale, Ariz., he worked for an asphalt and concrete supply company and had taken to stargazing on Saturday nights, traveling to a remote patch of desert with a telescope-owning friend, Jim Stevens.

Although Mr. Bopp had been marveling at the heavens since childhood, when his father took him outside to see the Perseid meteor shower, he was still a hobbyist, unfamiliar with the locations of many deep-space galaxies, nebulae and star clusters.

Stevens, a telescope maker who had become something of an astronomical mentor for Mr. Bopp, urged his protege to step up to the lens to gaze at a prominent cluster of stars in the constellation Sagittarius. A few minutes after 11 p.m., however, Mr. Bopp saw not just the cluster but also "a little fuzzy glow," he later told the Canadian magazine Maclean's. "I thought I had a faint galaxy or something."

Rather, Mr. Bopp — within minutes of another Southwest astronomer, 37-year-old Alan Hale — had discovered what is officially known as C/1995 O1, a dirty snowball of dust, rock and ice that went on to inspire a California death cult and light up the sky for hundreds of millions of observers around the world.

Mr. Bopp, who received a flurry of international attention and a form of scientific immortality from the Hale-Bopp comet that bears his name, died Jan. 5 at a hospital in Phoenix. He was 68.

The cause was liver failure, said his daughter, April Esch.

Mr. Bopp had never seen a comet before the summer of 1995, missing Halley's in 1986 and the disappointing smudge of Comet Kohoutek in 1973. But he and Hale, unusually similar in appearance, became the balding, portly faces of comet science for several months in 1997, when the Hale-Bopp comet came within 122 million miles of Earth, sported a tail millions of miles long and landed the two astronomers on an episode of the TV show "Bill Nye the Science Guy" and on ABC News with the shared title of person of the week.

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"I don't do much," Mr. Bopp told the Phoenix New Times, still taken aback at his newfound fame. "I have my work, my family, and I like to look at stars."

At various times on that night in July 1995, the stargazers believed they had discovered Comet Bopp, Comet Bopp-Stevens and Comet Hale, following an astronomical convention in which a comet's discoverers are credited by name.

Hale, who was unemployed at the time, had a doctorate in astronomy and had spotted dozens of comets outside his home in Cloudcroft, N.M. This one, he said in a phone interview, initially appeared as "just a dinky little fuzzball," showing no signs that it would eventually brighten and become visible to the naked eye.

Unaware of each other's observations, he and Mr. Bopp spent several minutes tracking the comet, ensuring that it wasn't a star cluster or some other object in the sky, before reporting their findings to the Central Bureau for Astronomical Telegrams at Harvard University, which has long been known for the announcement of newly discovered astronomical objects.

Unlike Hale, however, Mr. Bopp was standing in the middle of the desert, with spotty cell service and far from a computer he could use to send an email. He drove 20 miles to a truck stop, according to an account in People magazine, and when a Western Union representative told him there was no address on file to send a telegram to the Central Bureau, Mr. Bopp got in his car again and drove all the way to Glendale. He eventually found the address at home and placed the telegram, well after Hale had sent multiple emails with detailed coordinates for the comet.

By what he later remembered as "bizarre chance," Dan Green, the bureau's associate director at the time, was in the office Sunday morning when a call came from Western Union announcing Mr. Bopp's discovery.

"If I hadn't answered the phone," Green wrote in an email, "Bopp's name probably would not have gone on the comet's name," with Hale receiving sole credit.

Instead, both names were memorialized, with the two astronomers connecting the following day and developing an intermittent friendship on the lecture and television news-show circuits, booking enough appearances that Mr. Bopp effectively quit his job.

"I can find another job, but this is something that happens once in 10,000 lifetimes," he told Newsweek, referring to the comet's expected return in what was then estimated as 4897.

While the two stargazers tried to use the comet as a means of expanding public interest in astronomy, others saw it in prophetic terms. Several dozen men and women in a cult called Heaven's Gate viewed the comet as a means of ascending to heaven, and under the direction of leader Marshall Herff Applewhite killed themselves in a mass suicide in Rancho Santa Fe, Calif.

Mr. Bopp, whose finances were reportedly dwindling as the comet made its closest approach to Earth in spring 1997, faced his own personal tragedy. A brother and sister-in-law were fatally struck by a car while standing in the desert and photographing the comet.

"This," he told National Geographic days later, as photographs of the comet appeared on the covers of newspapers around the world, "has been the best week of my life. And the worst."

Thomas Joel Bopp was born in Denver on Oct. 15, 1949, and raised in Youngstown, Ohio. His father was a jeweler who gave 10-year-old Tom his first telescope, according to Sky & Telescope magazine. Mr. Bopp said his interest in the sky dwindled until his Air Force service took him to the Philippines, where he observed the optical phenomenon in which green flashes appear on the horizon during sunrise or sunset.

Mr. Bopp graduated in 1974 from Youngstown State University with a bachelor's degree in business administration and moved to the Phoenix area in 1980.

A marriage to Charlotte Carter ended in divorce. Survivors include his daughter, of Peoria, Ariz.; three sisters; two brothers; and a granddaughter.

Mr. Bopp worked as a Toyota dealership shuttle driver in recent years, and he continued speaking about the Hale-Bopp comet while volunteering at observatories in the Phoenix area.

"I just hope it inspires people to go out and look at the stars," he told the Phoenix New Times in 1996.