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Allegheny Observatory is put out to pasture
Sunday, April 23, 2000 By Dennis B. Roddy, Post-Gazette Staff Writer
Correction/Clarification: (Published April 26, 2000) A story in Sunday's editions on the Allegheny Observatory referred to its telescope, whose lenses were crafted by John Brashear, as the Brashear telescope. It is more properly known as the Thaw Memorial Refractor.
For 87 years, the 30-inch Thaw Memorial Refractor telescope atop Observatory Hill on the North Side has swept the heavens like a huge vacuum, amassing 111,000 photographic plates that cataloged the skies and helped pin down Earth's place in the milky wash of light that is the universe.
Now, almost a century after the Allegheny Observatory evolved into a research center where astronomers found two of the 32 known planets outside our solar system, it will all but cease as a ground-based observatory.
Tours by the public will replace the basic research in which it once reigned supreme.
The Thaw telescope, still held in wonder for its precision and workmanship, has been eclipsed by larger ground-based scopes in less cloudy regions, and by satellites that ring the Earth, pulling in data from a place where every moment is night.
"With all the satellites up there, it's getting pretty hard to compete," said George Gatewood, the observatory's director. The observatory's federal research grants have run out, with agencies directing their dollars to more advanced projects. Recently, the observatory laid off Tim Persinger, its chief technician, and Tom Reiland, the chief observer whose nighttime inspection of the skies compiled the data from which scientists like Gatewood deduced the presence of new bodies in the universe.
"The glamour work is the stuff that gets the headlines and the funding," said Jeff Chester, an astronomer at the U.S. Naval Observatory in Washington D.C., another astronomical institution that will shortly set aside its telescope's scientific work. In fact, the Naval Observatory will now work with Allegheny to crunch data from an ambitious satellite telescope due for launch in four years.
The Allegheny's plight is not unique. It is a tough time for ground observatories everywhere. John G. Radzilowicz, director of the Buhl Planetarium and Observatory at The Carnegie, all but shudders when he talks of the Royal Greenwich Observatory in England, where research ended long ago.
"For all practical purposes, it no longer exists," he said.
"I think we did all right up until the time the satellites started to fly," said Gatewood, whose computerized system for collecting data from the telescope -- known as the Multi-channel Astrometric Photometer -- extended the instrument's life.
But even though its grants are gone, Allegheny -- along with dozens of other observatories around the world -- is sitting on a hoard of photographic plates that chart the movement of stars over nearly a century. Only one third of those 500,000 photographic exposures have been measured on scientific equipment, meaning that Allegheny may well have discovered other planets, but has not yet discovered that it has discovered them.
"There's as much information on those plates as the European satellite collected," said Gatewood. The satellite, known as Hipparchus, named for a Greek astronomer, was launched in 1989 and collected data for more than three years. Most satellite telescopes have missions limited to a few years at most, and are moved out of the way to free their orbits for newer satellites.
Hipparcus had roughly the same precision as the Thaw telescope, but because of its position above earth's atmosphere, it could clearly measure activity around more than 100,000 stars, where Allegheny was able to focus on only 100 in the past 19 years.
When NASA launches the FAME (for Full-sky Astrometric Mapping Explorer) space telescope in 2004, Allegheny, along with the Naval Observatory and the Smithsonian Observatory in Cambridge, Mass., will receive data that will be sorted by their computers. The information is expected to cover 40 million stars at 20-times better precision than the large, refracting telescopes those observatories used.
"In other words," Gatewood said, "it's almost a perfect replacement for what we did from the ground."
What Allegheny did from the ground began in 1859, when three men from what was then called Allegheny City discussed the purchase of a telescope "the magnifying power of which would bring the heavenly bodies near enough to be viewed with greater interest and satisfaction."
They formed the Allegheny Telescope Association, bought a 13-inch scope from a Henry Fitz in New York City, and put up an observatory building on the North Side in 1861. The moon and planets were their focus.
In 1867, the observatory was donated to the Western University of Pennsylvania, forerunner to the University of Pittsburgh. S.P. Langley, a university professor who became the observatory's director, installed a transit telescope, which he used to determine star positions and, from them, get a more precise time of day -- something he sold to railroads and other time-sensitive businesses, generating almost $3,000 in annual income. (Langley later tried to become the first man to build a human-powered flying machine -- a steam-powered contraption he attempted to launch from a catapult -- but he was overtaken by the Wright Brothers).
It was Langley's successor, James Keeler, who drew up plans for a new observatory with a 30-inch refracting telescope. John Brashear, a famed local lens-maker, built the new scope, using lenses made from two glass discs cast by a German company. A later director then decided against using the scope as a visual refractor -- one through which an observer looks by eye. Instead, it was designed to use photographic plates, allowing the collection of data that could be inspected and measured later.
One of the major discoveries made by the Allegheny Observatory in the late 1895 was that Saturn's rings, once thought to be solid, were made up of billions of particles held in place by the planet's gravity.
But it wasn't the study of this solar system that made Allegheny important.
Unlike large reflecting telescopes, which pick up data by using huge mirrors, or radio telescopes, which measure waves given off by distant objects, refracting telescopes take direct light and magnify it through lenses, much the way a pair of binoculars does. Their precision makes them useful for collecting long-term information about star positions.
Photographic plates allow technicians -- Reiland is considered one of the best in the business at this -- to look for microscopic shifts in movement by distant stars. This "wobble" -- measurable only over long periods of time -- is one way to find distant planets.
Even though it can't be seen, a planet circling a distant star pulls that star slightly out of its direct orbit.
That was how Allegheny's team found that Lalande 21185, a star in the Ursa Major system, had two planetary "companions." The star is eight light years away, so the planets, roughly the size of Jupiter, could be "seen" only by the wobble in Lalande's movements in space.
Gatewood said he found these planets with the help of Reiland.
"Tom measured the plates and there was a wobble," Gatewood said. "This isn't an engineering feat. This is data that sits in a basement."
Since those days, the observatory's plate reader, a finicky, technical instrument able to detect the slightest movement on 8-by-10 inch photographic plates, has broken. There is no money to fix it and continue the important, if unglamorous, job of measuring the plates for evidence of other bodies picked up during this century.
"That's the kind of work that should be done," says Jim Phillips, the Smithsonian physicist whose own work on the FAME satellite is about to overtake ground-based observing. With 87 years worth of plates, Phillips said, the kind of long-term information that can be gleaned is significant.
"There are thousands and thousands of plates in vaults all over the world and nobody's measured them," said Chester, the astronomer at the Naval Observatory. "Who knows what's lurking there?"
What's even more remarkable than this trove of untapped information is how the Allegheny Observatory expanded understanding of the universe even though it was based in a city that was renowned for its smoke and soot, in which two-thirds of the night skies are often suffocated by clouds, said the Buhl Planetarium's Radzilowicz.
"It's amazing that we know as much as we do," he said.
The holy grail of astronomy, while few speak of it aloud, is the search for Earth-sized planets. So far, the technology of ground-based astronomy has allowed even the most careful observers to find only the big, gaseous, Jupiter-sized blobs circling stars such as Lalande.
"When it comes down to it, we really want to know if there are Earth-like planets, if there's potential for life there," Radzilowicz said.
Doing that from a hilltop in Pittsburgh doesn't seem likely just now. Still, there is valuable information sitting on those unanalyzed photographic plates at the Allegheny.
"Let's hope," Radzilowicz said, "they can find the money to analyze what they have."
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