Remembering John Dobson

The phone was ringing; I had a grinding tool in my hands. Could I pull the tool off the mirror, throw some water on my hands and answer the phone in time? In those days there were no smartphones, no answering machines; phones were tethered to the wall with a cord.

I managed to grab the phone off the hook my hands dripping with water and grit and say, “Hello”.  It was Rob on the other end, asking if I’d seen the article in the Register-Guard: something about telescopes and Crater Lake. News came by newspaper tossed on your doorstep by a delivery boy. This article was talking about “18 inch and 24 inch Sidewalk telescopes available for public viewing”. Rob was pretty excited. The year was 1981 and I was skeptical (I guess some things never change).

“Yes, I saw the article. But Rob, there’s no such thing as an 18 or 24 inch Sidewalk telescope. The reporter must be confused; he’s talking about the length of the telescopes. These scopes must be small refactors, maybe two or three inches in aperture”.

Telescopes were occasionally referred to by their length, since aperture very rarely exceeded several inches. Rob was insistent and besides, Crater Lake is a beautiful destination, he argued. So Saturday morning he swung by in his 1980’s van equipped with the latest gadget, a miles per gallon sensor and display, for us to play with on the drive. I said that some things never change. We talked telescopes on the way as the scenery changed from valley to forest, from fields to snow drifts, from valley air to crisp cool mountain air.

The final stretch into Crater Lake goes around breathtaking drop-offs and curves in the road, hiding our destination, the parking lot at the rim until the final curve. I stopped talking in mid-sentence. “Rob, those are giant telescopes – look!” Pointing out the obvious is all I could do. Before Rob could park the van and come to a full stop, I swung open the door and jumped out, running.

I couldn’t believe it: giant telescopes in cardboard and wooden frames. How could this be? A thin wiry guy was in charge, showing people views of the Sun and sunspots. One visitor from Sweden was arguing that the sunspots were not real. The guy in charge was practically yelling, “Those are sunspots. Each one is bigger than the Earth!” The visitor left unconvinced.

I didn’t quite catch the guy’s name. Did someone say, “John Dobson”? He was a force of nature though, a dynamic personality, and a way of talking that reminded me of cult leaders and gurus.

John showing Rob how to use the 24 inch.


John and the 24 incher.


The sidewalk astronomy setup at Crater Lake, 1981


I could not stop looking, teasing details from the sleeping scopes. There was not a single machined bolt or adjustment screw and the thin mirrors looked to be from plate glass. On the upper end were sliding tubes for focusers and recycled eyepieces. Impossibly crude and contrary to received wisdom.  Oh, and John’s son was catching a nap in one of the giant telescope’s tubes. John had named the telescopes with counterculture names like Delphinium and Stellatrope and ‘The Little One’ (which wasn’t so little). It was all so… different.

I felt tempted in a new way. I had the apple in my hand and couldn’t wait to take that first bite. We got in line and waited our turn at the 24 incher. Decades later I still find myself at a loss for words at those first views. Perhaps Ellie’s words from Sagan’s Contact, “I didn’t know, I didn’t know” come closest. We got in line again and again.

I asked John Dobson about the telescope’s details. He was more interested in talking about what we were seeing through the eyepiece and the universe we live in though he did talk at length about the materials used for the telescope’s motions. He didn’t build the scope for the scope’s sake; he built it to see the universe and to show the denizens of Earth our place in it.

Around midnight the crowd thinned. John suddenly announced that he was tired and going to bed. We could use the scope all night for ourselves as long as we locked it into position and aimed it away from the morning Sun. Are you kidding me? I thought of the contortions I had to go through for permission to use the 15 inch Cassegrain at Pine Mountain Observatory.

I’d looked through a couple of 24 inch Cassegrains. The view in Dobson’s 24 inch could not have been more different. The tiniest brightest colorful specks of light for stars, the dark field even though the Moon was rising. We stayed at the eyepiece all night, one person at the rear of the scope helping push it along and the other up at the eyepiece. It was our first introduction to the art of ladder observing. “A little more, yes… WOW!” This was quickly followed by the ladder shake from the person below. “Oh man, hurry up and look”.

Before we could catch our breath the skies brightened – it was 4:30am. We locked up the scope and headed to the van for the drive back in the morning sunlight. “I have got to build a 24 inch”, I kept repeating. Finally Rob slowed down and said, “If you say that one more time, I’ll throw you out and you can find your own way home!”

Within weeks I had ordered a 24 inch Pyrex blank from Corning in New York and began corresponding by letter with Bob Kestner, one of John’s protégés who would later, as a top professional optician at Tinsley, lead the effort to grind and figure the COBE corrective lenses for the Hubble Space Telescope.

John’s telescope design was opposite to all that I had learned. He used simple non-precision recycled parts. Everything had to be push-pull adjustable. The scope didn’t track, instead it used an altazimuth mount where the scope was pushed into position by hand and when let go, staying put, even in the night breeze. There was no shaking at the eyepiece. The vast majority of scopes of that era quivered in the wind, shaking after touching the focuser. The Cave Astrola 12 inch f8, a monster of a scope, the largest portable telescope that I had looked through, had a maddening dampening period at the eyepiece. One literally counted to twelve then looked through the eyepiece, being careful to not bump it with one’s eye. But John’s scope was nothing like that.

Moreover, his 24 inch, 18 inch and 12 inch mirrors were plate glass, a material that drew serious frowns from the experts. John had removed every item and accessory that was not absolutely essential to the task of viewing, simplifying the design and substituting stiff materials like wood and cardboard for metal. His mirrors floated on suspension arms, held in position with slings. Steve Jobs at Apple would become famous decades later for similar design aesthetics.

As I worked on my 24 inch, Mike and I planned a trip to Portland to scour the surplus ship yards for salvage plate glass. John had told me where he got his glass from surplus ship yards. Mike and I hopped from place to place. They all told us the same story. “Some white haired hippie from San Francisco came through a few years ago and bought up all the glass”. In desperation, we began looking around the yards, not taking the guy’s word who stood behind the counter.

Finally near the end of one Saturday I spied some glass in the back of this joint – a lot of it. The guy up front didn’t know about it, otherwise he would have sold it to John Dobson. We negotiated a price, $400 for a huge stack of glass weighing hundreds of pounds. We returned the next weekend with my station wagon. The guy had taken the least interesting half of the glass and moved it to the front, crossed his arms and insisted that this was all that there was the previous week. While Mike argued with him, I looked around and found the missing half in the back. I drove the station wagon to the back and loaded it up. On my return Mike’s eyes widened when he saw the glass. We quickly began covering it with the glass stacked in the front as the guy tended to other duties. This guy was ex-Marine ex-fighter and could have pounded the living daylights out of us just by glaring at us. I knew this was true because his tattoos said so. I gave him the check saying, “$400 for all the glass in the station wagon - that was our deal, yes?” I pointed to the station wagon, weighed down with glass. With an evil smile on his face, the guy said, “Yep”.

I drove out of there as fast as I could, the station wagon bouncing on its rear axle. Whew, we’d pulled off Mission Impossible. Jim Phelps would have been proud. At least until Mike said, “Say, Mel, that check you handed him. It had your address on it?” I lived in fear and closed the drapes and turned off the lights at night for several weeks until I was convinced the guy was not coming after me.

We had about 60 pieces of plate glass, mostly 12 inchers with a few 16 inchers. Mike immediately began a 16 incher – a size heretofore impossible to contemplate. Between what we turned into mirrors and what we sold, we kept busy for years, happily making mirrors with cheap materials that Mike would scrounge up: bags of titanium oxide for polishing compound and road tar for pitch. The thinnest glass served as tools.

My life would intersect with John’s from time to time. The most memorable was a week spent with Dobson at John Casino’s place in Seattle in 1989. Casino was finishing a 36 inch and needed help with the final tuning. As you can see from the Ronchigram, the mirror suffered from an overcorrected outer zone. Casino was experimenting with mirror mounts that warped the thin glass into a better figure.



Dobson in private was quiet, thoughtful and prone to thinking in long periods of silence. He talked about WWII, working for the war effort as a chemist, having his soul shaken when the atom bomb went off. He talked about China and his studies of eastern thought. He talked about sneaking out of the Vedanta monastery to get buckets of sand from the beach, sifting the sand into sizes to grind mirrors. I tried sand. It is tough going, grinding itself into mud almost instantly. What sheer determination John had to make mirrors from such crude materials.

John also talked me into the star test. John could do that; he could be quite convincing. John’s mirrors were outstanding; they gave superb star tests. They had rather long focal lengths, optimized to work with simple eyepieces to give the best magnification for sidewalk astronomy.

Later I found myself and my newly minted computerized telescope talking to John at an Oregon Star Party. He complimented me on my design.

John Dobson never strayed from his goal: showing as many people as possible the wonders of the Heavens so that they could first see, then understand. He was ignored by the establishment for years: Sky and Telescope's editor-in-chief famously writing that, "...your shortcuts...can hardly lead to satisfactory instruments of the kind most amateurs want in these large sizes. Porthole glass, makeshift wooden altazimuth mountings...are no longer suitable for telling thousands of other people who lack your knack of getting something "passable"." At the Riverside Telescope Makers Conference, a senior editor gave icy stares, refusing to look through Dobson’s telescopes because of the wooden slatted spider vanes, un-machined construction and psychedelic paint schemes. It is a cautionary tale that expertise can be at a loss when confronted by invention. Even after his breakthrough, John spent years trying to get his book, "How and Why to Make a User-Friendly Sidewalk Telescope", published. The book is unusual in that it combines product vision and simplified telescope making techniques, honed through the teaching of thousands of telescope and mirror making students.

What people failed to understand and sometimes do not understand today is the revolutionary nature of John Dobson’s design, taking advantage of a mix of precision parts where it mattered (large aperture thin plate glass mirrors, mirror mountings with floatation levers and slings, stiction based Teflon, cork and Formica movements) and non-precision parts where it did not matter (cardboard tubes, slide focusers, wooden altazimuth mounts). Through his perseverance and intelligence, John gradually came to understand what it meant to support large thin mirrors, materials that led to smooth high powered motions at the eyepiece and a mounting design that was rock solid. Prior to the Dobsonian, there was hardly a single telescope that I can remember that didn’t have some shake at the eyepiece, that didn’t have trouble making small motions at high magnifications.

John radically removed features that were not essential to the mission of showing objects through the eyepiece of a large aperture telescope. In particularly, John eschewed tracking mounts, expensive eyepieces and focusers. This made his design all the more compelling for its single mission to show people the heavens through large aperture telescopes.

Further, John developed mirror making techniques for large diameter thin plate glass mirrors and their mounting in a telescope. John was first to widely disseminate large pitch lap making techniques. He brought back to life star testing, first used successfully by John Hadley in 1722 to make the first true reflecting telescope with a parabolic mirror. Along with his sidewalk astronomy, we must never forget the countless telescope and mirror making classes he conducted over the decades, particularly up and down the west coast. He made mirror making accessible for anyone.

Further, it was a requirement of John’s that the design use inexpensive recycled materials. Since John did not invent a gadget or material (as he sometimes pointed out), his design could have been built decades prior. But it wasn’t, because no one thought of or put in the blood sweat and tears it took to create a revolutionary new design.

Today we celebrate design and understand its importance. Product design is the focus of individuals and companies worldwide. In John’s time, it was novel and misunderstood. For example, look at the early copies of his telescope design by some amateurs. They tried to add precision back in, walking away from the compelling simplicity of the Dobsonian. It took years for amateurs to appreciate the design. John’s students made numerous large aperture telescopes, introducing the era of the large aperture, low cost telescope in amateur astronomy. Through articles written by John’s students in Richard Berry’s Telescope Making Quarterly, the design and techniques spread like wildfire. Most popular was the 16 inch f5, a size and focal ratio that continues in popularity today.

John would say that the value of a telescope is in how many people look through it, not how burnished the wood. He put his design in the public arena, eschewing financial reward. John was proud of his design and pleased with the growth of sidewalk astronomy, though the world didn’t turn out exactly how he wanted: amateur astronomers too often focused on the telescope design rather than sidewalk astronomy; his cosmology fell into disfavor.

John was unfailing kind to me over the years. John was a force of nature that comes along once every few generations. John will be missed; the Earth is a lonelier place without him. But like a great comet, John will not be forgotten.

Mel Bartels, January 2014, upon John Dobson’s death at 98.