Some 1,500 years after stargazers began using rotating star maps to track celestial bodies’ journeys across the night sky, David Chandler figured out how to make the tool better.
One summer in the 1970s, Chandler struggled to use a traditional planisphere to pick out constellations in the darkness above North Carolina.
“This is a terrible map,” he said, jabbing at a copy of the one he used as it sat on his dining room table in south Denver on a recent Monday night. “It’s absolutely atrocious.”
Because the planisphere plotted a spherical sky on a flat surface, the stars were stretched and constellations distorted, particularly in the southern sky, making it hard to match the map to the stars overhead.
But that summer, Chandler figured how to get rid of much of that distortion: he made a new planisphere that was two-sided. One side best shows the northern sky, and the other side best shows the southern sky, eliminating most of the distortion.
“It’s a south polar projection of the side, masked off for use in the Northern Hemisphere,” Chandler said. “That was the reason everyone and their brother wasn’t doing this already, it’s enough of a twist of logic that I was the first kid on the block to start doing this.”
He printed the first 1,000 copies of his planisphere, “The Night Sky,” in 1976 when he was living in California, and tried hawking them to astronomy programs at junior colleges up and down the state. But his big break came when he attended a conference in Boulder and the design was spotted by someone from Sky & Telescope Magazine, the leading amateur astronomy magazine in North America.
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“He said, ‘Oh this is good, you got this right,’ and boom, everyone descended on my table,” Chandler said. The magazine went on to put in an order for 10,000 of Chandler’s planispheres, enabling him to get the company off the ground. Sky & Telescope also for years recommended Chandler’s planisphere as the best option for their readers.
“David’s innovation was to make the planisphere two-sided,” said Alan MacRobert, senior editor at Sky & Telescope Magazine. “…Making the whole thing much easier and user friendly, and less likely to send kids out with their parents to find the stars and get frustrated because they can’t match what Orion is supposed to look like with the sky.”
Chandler estimates at least a million copies of “The Night Sky” have sold since, though he hasn’t been involved with the company since the 1990s, when he gave up rights to an ex-wife as part of a divorce settlement.
Even when Chandler was involved in the company, he still kept his day job. Before he retired around 2012 and moved to Denver in 2018, Chandler, 73, spent 35 years teaching physics and math, mostly to high schoolers.
“I was born to be a teacher,” he said as he prepared to give a virtual presentation to the Denver Astronomical Society on the motion of the planets.
In retirement, Chandler launched a business, Math Without Borders, aimed at teaching math and physics to homeschoolers. He picked the best textbooks he’d ever used and created a series of digital courses, spending about a year recording each course.
“The math curriculum materials for homeschoolers is typically watered down, and my theory is it’s watered down for the comfort level of parents,” he said. “But that is not doing the kid a favor.”
He’s been focused on his teaching business more than the night sky lately, but Chandler said he is still drawn to astronomy.
“It’s nature on the grandest scale,” he said.
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