We spoke to an astronomy historian who's making sure we never forget about the world's oldest telescopes.
1693 manuscript documenting early astronomy. Image: Dioptrice, used with permission
There has never been an object that changed humanity’s self-perception as quickly or as completely as the telescope. It’s almost impossible to imagine what life was like before it. “How many stars have telescopes revealed to us which did not exist for our philosophers of old!” the philosopher/mathematician Blaise Pascal waxed in Pensées, referring to an era “of old” that was disrupted just 43 years earlier.
“The telescope transformed astronomy,” the science historian Stephen Case told me over the phone. “This is where Copernicus’s models went from being interesting mathematical models to being something we have evidence for.”
Case is wrapping up a PhD at Notre Dame on 19th century British astronomy and our changing perceptions of the stars (Spoiler: They’re just like us!), while also doing the graduate-student grunt work on the internet’s premier pre-1775 telescope archive, Dioptrice.
Starting in 2009, Marvin Bolt, then of Chicago’s Adler Planetarium, now of the Corning Glass Museum, and Michael Korey of the Mathematisch-Physikalischer Salon, in Dresden, have been recording and cataloging every old telescope they can find—starting with big museum collections like Adler’s, moving outward to English manor houses-turned-historical site, where someone back in the 1600s bought a telescope that’s sat in the collection without much thought since. Splitting his time between Notre Dame and Illinois, Case curates the collection and gets it online. Only a fraction of what they’ve found is up on the site now, but as the researchers get a better sense of what’s still around—some early telescopes were no more than parchment wrapped around a lens—they’re going to start seeing what the telescopes can see.
Okay, so that sounds pretty esoteric, and maybe it is, but the job of documenting the short wonderful life of early refracting telescopes—from 1608 to end of an era in 1775, when achromatic lenses became mass produced—attracted grants from both the National Endowment of the Humanities and the National Science Foundation, mostly because the early telescopes managed to knock the Earth and humanity out of the center of the universe all while those early astronomers were looking into the sky, literally, through a glass darkly.
“The early Galilean telescopes are notoriously difficult to use,” Case told me. “They’re difficult to find things with, and even once you find something with them it’s hard to know what you’re seeing.”
There’s a saying that “Computer science is not about machines, in the same way that astronomy is not about telescopes,” but a history of either science is inextricably tied to the limits of the technology it depends on. That said the limits of that technology is, to some extent, always determined by the user.
“William Herschel, the guy who discovered Uranus, says, ‘Even if you have a telescope as big as I do, you’re not going to see the things that I do because you’re not trained to see the way that I am,’” Case said.
What was Herschel seeing through his telescope? What was Galileo seeing? It’s hazy. For all its historical important, the history of the instrument is less than crystal clear.
Early telescope from the Adler Collection. Image: Dioptrice, used with permission
The first patents on the telescope were taken out in 1608 in the Netherlands, but before looking up, the telescope was first used for looking around. It was the cutting edge in military surveillance.
“When Galileo gets his hands on a telescope the first thing he does is he makes a gift of it to the Venetians,” Case said. “He says, ‘here, you can see enemy ships approaching.’”
Gerard Edelinck, 1671 Image: Dioptrice
When were they turned skyward? One of Dioptrice’s goals is to answer that question, which takes their scope (ugh) into manuscripts, illustrations and artwork from the 17th and 18th centuries. These questions of what a telescope is for, who is looking through it and what they’re looking for are cultural ones.
“We’re trying to figure out if these were originally seen as scientific instruments or as status symbols. Does your amateur gentleman natural philosopher just want to have one?” Case explained. “What we’re finding is that the telescopes are so ornate—quite lovely, really. They’re fancy, pretty objects. So they might be status symbols that people are buying them. Are they using them for astronomical observations? I don’t know. That also might be sampling bias, of course. If you have a telescope that you bought for looks it’ll stay around for longer than one you’re getting out every night at a university or for you own use.”
Some answers may not come until Dioptrice begins phase two: testing how well the telescopes work. Until recently the only way to do that was taking them apart, which museums are understandably adverse to, so Dioptrice plans to instead use adaptive optics and computer modeling to test them out. A light source is put on one end of the telescope that sends a grid through to the other side, where a wavefront detector watches the other end, and creates a map of the light’s path.
“Then you could model on the computer, say, an image of Venus or Saturn. And run that through the optical path, and this is what, physically, what astronomers could see, and the limits of what this telescope could observe,” Case said.
But according to Case the first step is just collecting all the data they can find. “Let’s be really empirical and really Baconian, and see how many of these instruments are still out there, where they are and what qualities they have,” he said, proving that astronomers speak exactly how you’d hope they would.
The internet might be known for having pornographic versions of absolutely everything that exists, but eventually, it’s also going to have archives of everything too. Naturally some will be porn, too, but at least one is of telescopes.