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John_Dobson

John Dobson. [via Sky and Telescope]

John Dobson died Jan. 15, 2014.  He was 98.

In 1968, when Dobson introduced his now-namesake methods to the San Francisco Sidewalk Astronomers, I was 15 years old and I’d just built my first telescope, including grinding the mirror. I made the mount, too, a standard equatorial mount made from cobbled i-together steel pipes and fittings. I wish I’d known then what Dobson was doing in San Francisco because then I’d have built one of the first Dobsonian telescopes.

Like many brilliant ideas, Dobson’s was simple and elegant. He used readily available materials to produce telescopes that were cheap, but superb mechanically and optically. My first mirror was 6″ because that was the biggest blank I could afford to buy. Back then, most amateur reflectors were 4.25″. A 6″ reflector was a serious telescope. I think the biggest amateur scope in the county was 8″, and people would have happily driven a hundred miles one-way for a chance to look through a 10″ scope. Dobson made huge instruments, 16″, 18″, and bigger. He didn’t have enough money to buy large mirror blanks, either, so he improvised. He made one 18″ mirror at a cost of literally $0. He used salvaged ship porthole glass.

But his mount was at least as important as his mirror innovations. A traditional equatorial mount for a scope the size of some of those early Dobsonians–18″ to 24″–would have cost about as much as a decent house. Dobson couldn’t afford that, so he improvised. He used scrap plywood, plastic, and other discarded items to build mounts that were stable, smooth, and intuitive to use. His mount is by far the most popular type among amateur astronomers, with millions in use worldwide.

I don’t know if Dobson qualifies as the first-ever maker, but he sure belongs on the honor role.

Editor’s note: Here are several projects inspired by Dobson:

A handmade Dobsonian telescope

Building a Dobsonian telescope

Making a portable Dobsonian telescope

Robert Bruce Thompson

Robert Bruce Thompson is the author of the Illustrated Guide to Home Chemistry Experiments and co-owner of the Home Scientist.


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