62 July 2014 sky & telescopeGary Seronik
Telescope Workshop
recently prompted me to refl ect on the
current state of the Dobsonian telescope. The fi rst was
the publication of this magazine’s February issue with my
review of the OneSky telescope from Astronomers With-
out Borders. Soon afterwards, I was saddened to learn
that John Dobson had died (S&T: April 2014, p. 71). My
path crossed John’s many times, and I fondly remember
serving as a telescope-making judge with him one year at
the Mount Kobau Star Party in British Columbia.
While considering John’s contributions to our hobby,
I couldn’t help but think about how the Dobsonian name
now applies to all kinds of scopes, including the OneSky.
If, however, the term were to refer to telescopes like those
John actually made (or at least those that refl ect his views
on telescope making), then the OneSky and many other
instruments wouldn’t qualify as Dobsonians. Why? First,
in the case of the OneSky and others of its ilk, it’s too
small. John felt that the size of instruments commonly
used in the 1960s and ’70s contributed to a kind of “delin-Two e v en t s
A Dob by Any Other Name
With so many variations, you might wonder when a Dob is really a Dob.
quency” and observing paralysis. He thought that most
people back then looked endlessly at the same things
because they were aperture-limited. The bigger the better,
so far as John was concerned.
Second, John never built anything that didn’t have a
conventional, solid tube. I remember walking the hill at
Kobau with him when we came upon a nice 16-inch truss-
tube Dob that my friend Lance Olkovick had built. John
was impressed with the scope’s portability, and though he
didn’t express disapproval of the truss design, he never
made one himself.
Third, hands up — how many people think that short-
focal-ratio mirrors are a Dobsonian innovation? If you
raised your arm, you’re not alone. Instruments with focal
ratios around f/4.5 are commonly called Dobsonians. Yet
John never liked fast scopes. His scopes were usually never
faster than f/6. The f/4.5 variation originated with the
long-defunct Coulter Optical Company. Its f/4.5 Dobso-
nians were so popular that the focal ratio became regarded
as one of the Dobsonian’s defi ning characteristics!
In its original form, the Dobsonian was a Newtonian
refl ector made with inexpensive materials; it moved on
an alt-azimuth mount made of wood with Tefl on-and-For-
mica bearings; and it sported a big, thin primary mirror.
John’s entire reason for building telescopes was to get as
many people as possible to see the universe fi rsthand. He
didn’t want expense, aperture, or utility to be barriers.
Of course, there’s no putting the genie back in the
bottle. Today, the term Dobsonian is attached to all man-
ner of scopes, regardless of what John himself built or
blessed. And as ATMs continue to push the limits of what
a big-aperture, alt-azimuth Newtonian looks like, so will
the range of instruments bearing the Dob descriptor.
In spite of the Dobsonian design’s popularity, John was
never publicly comfortable taking credit for it. He used
to say that he didn’t like it when telescopes were named
after their inventors. He’d joke, “Maksutov Schmaksutov,
Newtonian Schnewtonian, Dobsonian Schmobsonian,
Schmidt, Schmidt!” He always laughed at that one. ✦Contributing editor Gary Seronik is an experienced telescope
maker who has built a few “real” Dobsonians, some of which
can be seen on his website, http://www.garyseronik.com.At Canada’s Mount Kobau Star Party, John Dobson (right)
and Lance Olkovick discuss Lance’s newly completed
16-inch truss-tube Dobsonian.
GARY SERONIK