David Chandler has helped thousands of people find the stars

Some 1,500 years after astronomers began using rotating star maps to track celestial bodies’ journeys across the night sky, David Chandler discovered how to improve the tool.

One summer in the 1970s, Chandler struggled to use a traditional planisphere to locate constellations in the dark over North Carolina.

“It’s a terrible map,” he said, pointing to a copy of the one he used as it sat on his dining room table in South Denver on a recent Monday night. . “It is absolutely excruciating.”

Because the planisphere traced a spherical sky on a flat surface, the stars were stretched out and the constellations distorted, especially in the southern sky, making it difficult to match the map with the stars above.

But that summer, Chandler figured out how to get rid of much of that distortion: he made a new two-sided planisphere. One side shows the northern sky better, and the other side shows the southern sky better, eliminating most of the distortion.

“It’s a south polar projection from the side, masked out for use in the northern hemisphere,” Chandler said. “That was the reason why everyone and their brother weren’t doing this already, it makes sense that I was the first kid in the neighborhood to start doing this.”

Helen H. Richardson, The Denver Post

The two-sided planisphere created by David Chandler pictured at his home on November 8, 2021, in Denver.

He printed the first 1,000 copies of his planisphere, “The Night Sky,” in 1976 while living in California, and attempted to sell them to astronomy programs at junior colleges around 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, North America’s leading amateur astronomy magazine.

“He said, ‘Oh, it’s okay, you got that right,’ and boom, everyone came down to my table,” Chandler said. The magazine then placed an order for 10,000 of Chandler’s planispheres, allowing it to get the business off the ground. Sky & Telescope has also for years recommended Chandler’s world map as the best option for its readers.

“David’s innovation was to make the planisphere double-sided,” said Alan MacRobert, editor-in-chief of Sky & Telescope Magazine. “… make it a lot easier and more user-friendly, and less likely to send kids 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 that at least a million copies of “The Night Sky” have since sold, although he has not been involved with the company since the 1990s, when he waived his rights to an ex- woman in divorce settlement.

Even when Chandler was involved in the business, he still kept his day job. Before retiring around 2012 and moving to Denver in 2018, Chandler, 73, spent 35 years teaching physics and math, mostly to high school students.

“I was born to be a teacher,” he said as he prepared to give a virtual presentation to the Denver Astronomical Society on the movement of planets.

In retirement, Chandler started a business, Math Without Borders, to teach homeschoolers in math and physics. He chose the best textbooks he had ever used and created a series of digital courses, spending about a year recording each course.

“The math curriculum material for home students is generally watered down, and my theory is that it is watered down for the comfort level of the parents,” he said. “But that doesn’t do the kid a favor.”

In recent times he has focused more on his teaching activity than on the night sky, but Chandler said he’s still drawn to astronomy.

“It’s nature on a large scale,” he said.

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