ASTRONOMER’S WORKBENCH by Jerry Oltion
A 3D-Printed Binoscope
No workshop? No problem.
WHEN ROBERT ASUMENDI looked
through Frank Szczepanski’s binocular
telescope (S&T: Apr. 2019, p. 72), he
realized several things at once:- Binocular vision is vastly more
comfortable and pleasurable than
monovision. (So much so that Hans
Lippershey had to build a binocular
before the patent offi ce would even
consider his patent application for
the telescope in 1608.) - Binocular vision helps to compensate
for Robert’s severe astigmatism. - Despite wanting a binocular scope,
he also wanted grab-and-go portabil-
ity, wide fi elds, and enough aperture
to provide satisfying views of deep-
sky objects.
Robert searched for a scope that would
satisfy all his requirements but came
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up empty. “There’s no commercial
scope that delivers all those things,” he
reports. “So I made it.”
Robert faced two simple challenges:
He had never built a telescope before,
and he didn’t have any shop space. He
did, however, have a couple decades of
experience with computers. “So my com-
puter became my workshop,” he says.
“I designed everything in a parametric
computer-aided-design (CAD) program.”
And because we’re now living in the
21st century, 3D-printing the parts
became a natural outcome of the design
process. That allowed Robert to test
aspects of his design without building
the entire thing at once. He could exam-
ine a real physical object, modify its
parameters in the computer, and print
another to see how it worked. He didn’t
have a 3D printer at fi rst, so he jobbed
out his designs on 3DHubs (3dhubs.
com), an online printing service. That
worked nicely, but he quickly realized he
wanted a 3D printer of his own. Besides
eliminating shipping costs, it made
unit-testing of small components more
practical and allowed him to optimize
settings for each part, which made for
fantastic, repeatable results.
He started with the focusers. He
wanted to use 2-inch eyepieces, but he
couldn’t fi nd any commercial focus-
ers that would put the drawtubes close
enough together for most people’s
interpupillary distance (t he spacing
between eyes). He settled on a modifi ed
Crayford design that allows the draw-
tubes to nearly contact each other. And
once he’d started designing, he just
kept going. Could he 3D-print a fi lter
wheel? Could he 3D-print the second-
ary mounts? Could he design channels
in those secondary mounts to runwires for dew sensors and heaters?
He could, and did. It was an iterative
process, each step building on the previ-
ous, both intellectually and physically.
Robert says, “The resulting parts would
have been extremely diffi cult, costly, or
heavy to machine. The unique honey-
comb structure of 3D prints lets you
design lightweight, sturdy components
that just wouldn’t work in other materi-
als. And, of course, with a binoscope
you need two of everything, and several
of the components are mirrored. With
3D printing, you just use the mirror
command and print another one.”tRobert Asumendi’s “Drifter” binocular tele-
scope is a marvel of design and execution.pTop: The eyepiece adapter fi ts solidly into
the focuser thanks to neodymium magnets
embedded in each part. Bottom: The 3D printer
generates an eyepiece adapter. This piece took
about 20 minutes to print and cost about $1.65
in materials.