Adler Planetarium

Remembering John Dobson

When I was a boy growing up, I longed to look at the stars through a telescope. I'd lay out in my backyard, staring up at the stars and Moon, and wonder what they would look like up close.

My mom has an old Bushnell spotting scope that she uses for birding.  It wasn't large, but she let me use it to look at the Moon, and it blew my socks off!  I could see craters, and mountains, and ever-changing shadows. I carefully traced the outlines of vast lunar plains on maps, matching it to what I could see, and in my minds eye I walked on the Moon, following the trails of the Apollo astronauts.

A Bushnell spotting scope.

A Bushnell spotting scope.

The spotting scope showed me things I could never see with my naked eye. It was by all accounts about the same as one of Galileo's telescopes.  But I wanted to see more.  I wanted a telescope that would plunge me deep into the dark velvet of the sky, gathering the misty light from galaxies that had left on a long journey Earth millions of years before.  But big telescopes were expensive, and I filed that dream in the back of my mind next to other unobtainable things: a personal submarine, a hang glider, and a subterranean lair buried under my parents backyard.

Unbeknownst to me at that time, a quiet revolution was taking place in telescope design. It had started shortly before I was born in a club known as the San Francisco Sidewalk Astronomers. One of the co-founders was a man named John Dobson, who advocated what was then considered to be craziness among telescope aficionados: build a telescope with whatever you can find and scrounge up, it doesn't have to be perfect; don't worry about tracking the stars, just build a stable mount that rotates so you can point to where ever on the sky you need to.  John called his telescope design a "sidewalk telescope," but today it is universally known as a "Dobsonian."

Dr. Shane L. Larson and his two Dobsonian telescopes.

Dr. Shane L. Larson and his two Dobsonian telescopes.

The Dobsonian design revolutionized astronomy for three reasons.  First, they were cheap and easy to build, which meant uncountable numbers of people who could not have afforded a telescope before now had easy access. Second, they were easy to take apart and set up, which meant they were easy to transport.  And third, the design was very stable, allowing huge telescopes to be built; with bigger telescopes, people could see much more in the Universe than ever before.

By the time I was in college, the Dobsonian revolution was in full swing. At an opportune moment I was exposed to the idea, and built my first telescope, realizing that age old dream from my childhood.  Today I own two Dobsonian telescopes --- one that I can easily cart around, and one that is quite a bit larger!  And I owe it all to John Dobson, who had the remarkable audacity to think about telescopes in a way that had not been thought before.

Sadly, John Dobson passed away on 15 January 2014 at the age of 98. He was, for all the years I have been in astronomy, intimately involved in helping people build and own telescopes, and using them to see the sky.  He has been a great inspiration to untold numbers of us, and brought the Universe closer to more people than any other person has before.  He will be sorely missed!

Written by Shane Larson, astronomer at the Adler Planetarium.

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