CASTEL GANDOLFO, Italy — The Vatican Observatory at the papal palace at Castel Gandolfo was host for several days in early June to 90 professional and advanced amateur astronomers. Half of them observed from the roof of the palace overlooking Lake Albano in this hillside town south of Rome the June 8 transit of Venus.

The Specola, as the Vatican Observatory is also called, is not only one of the most highly respected observatories in the world but also is one of the oldest astronomical institutes. It dates back to 1582 when Pope Gregory XIII formed a committee to look at the scientific data and ramifications involved in a reform of the calendar.

The guests were part of a group organized by the American astronomy magazine Sky & Telescope, whose assistant editor, Imelda Joson, and her husband were the only two people in the group of 40 to have previously visited the Vatican Observatory.

The second half of the group viewed the celestial event from a site at a nearby town and visited the observatory June 10.

Sky & Telescope titled the June 8 event “Venus Has Its Day in the Sun” and noted in a report from Rome that “the rain and clouds that had persisted for days suddenly cleared up after 4 a.m., and observers watched the transit with perfect skies.”

An astronomical “transit” is the passage of one object in the sky in front of another: In this case, Venus passed between Earth and the sun. Because this event occurred before sunrise in the Western Hemisphere, astronomers from Canada and the United States came to Europe for the viewing.

One of the Jesuits present at the June 8 transit, Brother Guy Consolmagno, explained that because proper equipment is necessary to safely observe the transit and the sun, the Tucson-based Coronado Technology Group, in preparation for the event, gave the Specola a telescope especially equipped for solar observation. It was presented May 31 to Jesuit Father George Coyne, director of the observatory, at Castel Gandolfo.

“The new telescope,” Brother Consolmagno said, “is very small and very elegant. We simply strapped it to the side of one of the larger telescopes we have at the observatory. Its special optics were designed to allow astronomers to look safely at the sun.”

He said they took many photos June 8, including some through the telescope and others using both webcams and TV cameras.

The rare transits of Venus happen in pairs, eight years apart, separated by 130 years. Since the invention of the telescope, only five such transits have occurred, the last on Dec. 6, 1882. There will be one other transit this century, on June 6, 2012. Venus was approximately 60 million miles from the Earth on June 8 during the six-hour transit.

Brother Consolmagno said one reason the Specola welcomed guests was part of a continuing effort to show how the Church embraces science. He said he thought the Vatican was the drawing card in getting so many people, including a Presbyterian minister who is an amateur astronomer, to sign up for the trip.

A native of Detroit who was an astronomer with a degree from the Massachusetts Institute of Technology in planetary sciences before entering the Society of Jesus in 1989, Brother Consolmagno has been at the Specola since 1993. He spends part of his year at the Castel Gandolfo headquarters of the Vatican Observatory and another part in Tucson, where the principal telescope used in their work — the Vatican Advanced Technology Telescope — is located.

The Jesuit astronomer, whose enthusiasm about his science is contagious, called the reaction to the June 8 transit “fascinating.”

“I expected people to cheer or laugh or applaud, but instead there was a profound silence,” he said. “The transit was not a spectacular event but rather a sublime moment because of its rarity and history. There was a sense of the wondrous predictability of it all, a sense that this was so beautifully predicted hundreds of years ago and it occurred right on schedule. Nonetheless, to see it happen — as predicted — gives you a sense of wonder.”

“There is so much chaos in the universe,” he continued, “yet this gave you an emotional sense of ‘some things work’ in the universe. Here, on June 8, it worked.”

Brother Consolmagno explained that long before the invention of satellites and today's highly sophisticated measuring instruments, events such as transits were used to calculate distances in the universe. Transits were used, for example, by English astronomer Edmund Halley (of Halley's comet fame) in celestial mechanics, which is the mathematics of predicting where planets are supposed to be. A close friend of his was Isaac Newton, and Newton's theory of gravitation greatly influenced Halley's work.

Asked what special attributes a person needed to become an astronomer, Brother Consolmagno replied, “a pair of eyes, a sense of logic, enthusiasm and patience. Many brilliant astronomers, self-taught, had only these qualities.”

If enthusiasm alone could make one an astronomer, Brother Consolmagno could transform armies of people into stargazers.

Joan Lewis works for Vatican Information Service.