On a warm, spring day in 1974 I planned a visit to the California Academy of Sciences in San Francisco's Golden Gate Park. But I never made it inside because a collection of telescopes set up on its front portico caught my attention. All had strange but simple altazimuth mountings, and all were pointed at the Sun. In their midst stood a few amateur astronomers led by a frail-looking man in his late 50s, who was explaining the miracle of sunspots to a watching crowd. Then I realized that this shirtless man with a ponytail was none other than the telescope-making wizard John Dobson.
Since there were more telescopes than people to run them, I offered to help. The next two hours were a revelation, as I watched Dobson and his San Francisco Sidewalk Astronomers in action. "Our only reason for being is to show the sky to the people," Dobson told me. "Let other clubs do research with fancy telescopes. We want to share the sky with everyone."
Dobson religiously believes in making telescopes with the simplest materials and by the simplest procedures. He is like the 19th-century American naturalist and author Henry David Thoreau, who opened his masterpiece, Walden, by borrowing an axe so he could begin work on his pondside home. But Dobson takes the Walden concept a step further, because he uses his simple creation to show the universe to as many people as care to look.
"I want a telescope in every driveway, on every sidewalk!" he trumpets. "We don't make telescopes for us to use in our backyards and then go to bed," he snaps. "We make simple scopes for the people to use."
And that is the heart of the Dobson Revolution.
Eighty years ago this September 14th, Dobson was born in Beijing, China. His father was then teaching zoology at Beijing University. In 1927 the Dobson family, including his parents and three brothers, moved to the United States. They stopped briefly in San Francisco, intending to move on, but because of lack of funds -- a circumstance that would become Dobson's lifelong badge of pride -- the family stayed there.
In the fertile environment of Golden Gate Park, Dobson's parents provided their children with most of their schooling. In 1934 Dobson enrolled at the University of California in Berkeley. In his book How and Why To Make a User-Friendly Sidewalk Telescope, Dobson reveals that he did this "for the sole purpose of finding out how to keep Einstein alive." From those early days, Dobson became interested in cosmology, and he believed that Einstein was our best hope to "get the cosmos figured out."
After several interruptions in his schooling -- which included joining the Carol Beals dance group, which specialized in politically motivated dramatizations -- Dobson graduated in 1943 with a degree in chemistry and mathematics. He quickly found jobs in war-related fields at Caltech and at the Berkeley Radiation Laboratory.
On May 8, 1944, his life utterly changed course. On that day Dobson entered a Vedanta monastery, part of the Ramakrishna religious order. Located near the San Francisco marina, the monastery ran a strict daily schedule that began with rising at 4:45 a.m. for worship, study, and meditation. During his stay, Dobson increased his efforts to understand how the universe ticked. He believed that contemplating the universe would not be complete without seeing it in detail. The question "Why do we see what we see?" has occupied Dobson's mind since his youth. By the early 1950s Dobson decided to make a telescope so he could at least see more of the universe for himself.
His first telescope combined an achromalic lens of 14-inch focal length with an eyepiece scrounged from an old pair of binoculars. The 37x telescope was a start, but by 1956 Dobson wanted something bigger. He remembered a 12-inchwide porthole glass lying on a friend's tabletop -- maybe used as a trivet -- and offered lo turn it into a telescope.
With the help of Allyn Thompson's book Making Your Own Telescope, Dobson soon completed the instrument and turned it on the last-quarter Moon. Our neighbor in space looked so close he felt he was about to land on it. He immediately formed a principle that would guide him for the next four decades: If you own a telescope, it is your duty to share it with people who don't.
Despite the rigors of monastic life, Dobson began making telescopes for others. He'd use whatever materials he could find -- even the bottom of a gallon jug was good raw material for a mirror. For abrasive, he'd collect sand and separate it by size -- just as William Herschel had -- with mesh screens he designed himself. And from available gardening supplies he made polishing rouge. Two years later Dobson was transferred to another monastery, in Sacramento, where he continued building telescopes.
On some clear evenings Dobson would sneak out of the monastery and roam the nearby streets with his 12-inch 1/7 telescope perched atop a station wagon, to offer passersby a glimpse of the heavens. If a youngster showed serious interest in the sky, Dobson would speak to the child's parents and offer to lend them the telescope free for a month. Eventually he helped some of these people make their own telescopes -- all while AWOL from the monastery. He knew he was jeopardizing his career doing this. "Either I could tell these kids to go to hell," he figured, "or risk getting thrown out of the monastery. I wasn't going to tell them to go to hell."
By the time he had finished fifteen 12-inch and two IX-inch telescopes for various households, the monastery, which had grown suspicious of his frequent absences, discovered his nocturnal activities. Dobson was warned to give up telescope making or face expulsion. He desperately wanted to stay, but eventually he was asked to leave (S&T: November 1989, page 530).
Dobson never lost his monastic spirit; in fact, he continued to live the spartan way in the outside world. He slept on a friend's rug, ate sparsely, and every clear night set up his 12-inch telescope he named Stellatrope at the corner of Jackson and Broderick Streets. Soon he began giving lectures on telescope making, first at a local Jewish Community Center and later at various places in the Bay Area.
The first telescope Dobson made didn' t fare well. Rumor has it that the monastery's abbot, Swami Ashokananda, ordered the telescope disposed of and allegedly had it tossed into San Francisco Bay. That was a tragic night for amateur astronomy.
In 1968 Dobson and Bay Area amateurs Bruce Sams and Jeff Roloff started a new kind of astronomy club. The San Francisco Sidewalk Astronomers, as it was called, would do no research and hold no formal meetings -- its sole purpose was to share the sky with the public (S&T: April 1980, page 338).
Eventually the club acquired an aging school bus, dubbed Starship Centaurus A. For nearly a decade it served as the roving club's bedroom and telescope storage shed. The bus died in 1978 during the return trip from a star party at the Grand Canyon. Fortunately, the growing fame and reputation of the San Francisco Sidewalk Astronomers led the Skaggs Foundation to award them a modern motor home. With these more comfortable quarters the group continued its raison d'etre: "have telescopes, will travel."
Pamela Reid, the secretary of the Sidewalk Astronomers' Los Angeles branch, fondly recalls the day in 1979 when Dobson set up a telescope in the front yard of a local church. Several years later he also helped Reid finish her 8-inch mirror. She was impressed at how quickly Dobson diagnosed the mirror's condition. "I watched him turn my disastrous attempt at mirror grinding into a success in 35 minutes," she says. "He just knew what the mirror's problems were."
Dobson had to struggle to get his telescope-making and testing methods accepted by the larger amateur community. His earliest attempts were rebuffed. Sky & Telescope's founding father, Charles A. Federer Jr., for example, doubted in 1969 that Dobson's simple plywood mountings and lightbulbtesting procedures would be of any use to serious observers. Federer missed Dobson's point. Dobson was not after perfection -- he was after the simplicity with which practically anybody could build, own, or use a big scope.
But once the design caught on, it was Dobson himself who did the underestimating. At all major star parties these days the Dobson-type telescope is by far the most common. At Florida's Winter Star Party each year, many stand like trees in a spot now called the Valley of the Dobs (S&T: August 1995, page 107).
What defines a Dobsonian telescope? Dobson, by the way, objects to the moniker. He says applying his own name to a class of telescope is anathema to him, quipping, "Cassegrain, Schmasse-grain! Maksutov, Schmaksutov! Dobsonian, Schmobsonian!" He believes Richard Berry first coined the term "Dobsonian" in Telescope Making.
A sidewalk telescope, as Dobson calls his creation, is not just any telescope with a plywood-box altazimuth mount. It is a Newtonian reflector with a lightweight mirror, usually made of porthole glass. The mounting uses plywood and Teflon strips to ease the motions in azimuth and altitude.
The original 12-inch sidewalk telescope used roof shingles to support the secondary. Its tube was made of readily available materials. For example, since Dobson could not afford a Sonotube, he used the cardboard cores of discarded garden-hose reels. Each reel core was 22 inches long. If it took three such cores to fashion a tube, Dobson would call it a three-barrel 12-incher. Today, most of the telescope tubes are converted Sonotubes.
Some people say that Dobson's approach encourages sloppiness. The idea of using inexpensive lightbulbs to test a mirror might appear to work in principle but leads to inaccurate results in practice. Dobson counters that argument by saying that he and his sidewalk astronomers are interested in public service, not laser testing and technogadgetry.
On September 2nd Dobson's beloved Sidewalk Astronomers plan to toast him with a big celebration at San Francisco's Randall Museum (see facing page). With sidewalk telescopes all over the place, the people of San Francisco, with flowers in their hair and stars in their eyes, will look at the universe that Dobson has been trying to comprehend all his life. And on that night he will do what he always does: he will ask people to look, and to think. It doesn't matter that they might not agree with him, but it does matter that they think about it. What better way to celebrate a man's dream?
Since 1988, David Levy has featured the lives of some the most illustrious members of the astronomical community.
Subscriptions to Sky & Telescope: To order from the U.S. and Canada, call 800-253-0245, Monday Friday, 8:30 a.m. - 5 p.m. Eastern Time. U.S., Canadian, and international inquiries may also be mailed to PO Box 9111, Belmont, MA 02178-9111 or faxed to 617-864-6117.
Dobson is renowned for his innovative, unorthodox telescope-making ideas. His 90-minute instructional video, Telescope Building with John Dobson, is available for: $39.95 from Dobson Astro Initiatives, P.O. Box 460915, San Francisco, CA 94146.
Free public viewing and lecturing have been Dobson's mission all his life. He and his Sidewalk Astronomers have logged tens of thousands of miles with their telescopes, setting them up at street corners, parking lots, shopping malls, star parties, and state parks. And they are still going strong.