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
“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
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
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
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
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
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. Testament to his mirror making skills was an optics
award at the Riverside Telescope Makers Conference in 1971. 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.
PS Check out the youtube video, especially John's students working on the Hubble Space Telescope COSTAR corrective optics